• I want the data to be processed  and shown to the user as quickly as possible.
• If the file is large I don’t want to have to store the entire contents in memory.

Using NSXMLParsers initWithURL: method the xml file is downloaded synchronously with NSURLConnection before parsing. If NSXMLParser was able to begin as soon as stream buffer began to fill, even though the overall parsing time wouldn’t be reduced significantly if the updates are immediately displayed the user perceived time decreases significantly.

Using the excellent objective c expat wrapper library by Robbie Hanson as a base iPhoneExpat uses CFNetwork & CFHTTPMessage to create and feed a http stream gradually into Expat. If the server supports gzip compression zlib is used to decompress the stream on fly.

iPhone Expat offer 3 methods for initialization

- (id)initWithContentsOfURL:(NSURL *)url;
- (id)initWithContentsOfFile:(NSString *)path;
- (id)initWithData:(NSData *)data;

The delegate messages are also a drop in replacement for NSXMLParser

@protocol ExpatXMLParserDelegate 
 
@optional
- (void)parserDidStartDocument:(ExpatXMLParser*)parser;
- (void)parserDidEndDocument:(ExpatXMLParser*)parser;
- (void)parser:(ExpatXMLParser*)parser didStartMappingPrefix:(NSString *)prefix toURI:(NSString *)namespaceURI;
- (void)parser:(ExpatXMLParser*)parser didEndMappingPrefix:(NSString *)prefix;
- (void)parser:(ExpatXMLParser*)parser foundComment:(NSString *)comment;
- (void)parser:(ExpatXMLParser*)parser foundProcessingInstructionWithTarget:(NSString *)target data:(NSString *)data;
- (void)parser:(ExpatXMLParser*)parser parseErrorOccurred:(NSError *)parseError;
- (BOOL)parser:(ExpatXMLParser*)parser shouldProcessAttributesForElement:(NSString *)elementName;
 
@required
- (void)parser:(ExpatXMLParser*)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict;
- (void)parser:(ExpatXMLParser*)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName;
- (void)parser:(ExpatXMLParser *)parser foundCharacters:(NSString *)string;
 
@end

However

- (void)parser:(ExpatXMLParser *)parser foundCharacters:(NSString *)string;

Will report the entire contents of a tag so you don’t need an NSMutablestring to buffer fragments in your delegate. e.g.

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
	[buffer release];
	buffer = string;
	[buffer retain];
}

Should be good in 99% of cases to get the entire contents of a tag

The project can be found here

http://github.com/zootreeves/iPhoneExpat

Alternatively checkout the code using git: http://github.com/zootreeves/iPhoneExpat

Benchmark test output:

I’ve included a test application which sequentially downloads and parses the following feeds:

@"http://ax.itunes.apple.com/WebObjects/MZStoreServices.woa/ws/RSS/topalbums/sf=143441/limit=300/explicit=true/xml",
@"http://ax.itunes.apple.com/WebObjects/MZStoreServices.woa/ws/RSS/topalbums/sf=143441/limit=300/explicit=true/xml",
@"http://feeds.feedburner.com/DilbertDailyStrip",
@"http://designsponge.blogspot.com/atom.xml",
@"http://www.slate.com/rss/",
@"http://rssfeeds.usatoday.com/UsatodaycomBooks-TopStories",
@"http://googleblog.blogspot.com/atom.xml",
@"hhttp://api.flickr.com/services/feeds/groups_pool.gne?id=61057342@N00〈=en-us&format=rss_200",
@"http://phobos.apple.com/WebObjects/MZStore.woa/wpa/MRSS/topsongs/limit=25/rss.xml",
@"http://www.readwriteweb.com/rss.xml",
@"http://rssfeeds.usatoday.com/UsatodaycomNation-TopStories",
@"http://dictionary.reference.com/wordoftheday/wotd.rss",
@"http://www.quotationspage.com/data/qotd.rss",
@"http://sports.espn.go.com/espn/rss/news"

Time to reach the first element Expat: 8.611217 — NSXMLParser: 15.404100
Total time for Expat: 10.902272 — NSXMLParser: 17.108309

Memory is also reduced by a factor of about x4 (see screenshots)

Further Considerations

• It would be great if http requests were persistent, however after setting kCFStreamPropertyHTTPAttemptPersistentConnection to true using httpscoop I will still able to intercept “connection close” messages between requests to the same server. I think I must be doing something wrong here.
• It would be preferable if as many objects as possible were released manually rather than using an autorelease pool. For example the delegate methods that pass an elementName it is common for the client to use this string to determine their current tag, but rare that they actually want to retain it. The code could be altered so these strings are not placed in a pool and are released immediately after the delegate message is sent. Not only can the overhead of collection be avoided but CFStringCreateWithCharactersNoCopy can be used as well.
• With UTF8 creating CFStrings with the [NSString stringwithutf8string:] was no problem. However when I configured Expat to use UTF-16 characters internally I found that CFStringCreateWithCharacters would often return garbage. The problem is I was passing in UINT16_MAX as the buffer length hoping that the CFString would be terminated at null, however it doesn’t work that way and I had to change everything to calculate the buffer size using UniCharStrlen(buffer) before hand.
• FTP (CFFTPStream) and file streams could easily be supported.

The animated intro was achieved using CoreAnimation to drop UIButtons from the top of the screen. The “multi value fields” used in the search screen are simply UILabels embedded in a UIScrollview using the paging feature to provide smooth scrolling between values. There are existing Calendar libraries for the iphone however I decided in the end to write a custom control which allows much tighter integration into the design.

JCJ Locums app is available free on the app store

The code below is provided under an MIT license, but if you do make any updates it would be great if you could send them back.

Usage:

   //Example to download google's source and print out the urls of all the images
   NSError * error = nil;
   HTMLParser * parser = [[HTMLParser alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://www.google.com"] error:&error];
 
   if (error) {
     NSLog(@"Error: %@", error);
     return;
  }
  HTMLNode * bodyNode = [parser body]; //Find the body tag
 
  NSArray * imageNodes = [bodyNode findChildTags:@"img"]; //Get all the <img alt="" />
 
 for (HTMLNode * imageNode in imageNodes) { //Loop through all the tags
       NSLog(@"Found image with src: %@", [imageNode getAttributeNamed:@"src"]); //Echo the src=""
  }
 
  [parser release];

You can grab a copy of the code here on github:
http://github.com/zootreeves/Objective-C-HMTL-Parser
git@github.com:zootreeves/Objective-C-HMTL-Parser.git

Note:

-(NSString*)rawContents; does not work, you need to use NSString * rawContentsOfNode(xmlNode * node, htmlDocPtr doc); to dump the entire html contents of a node.

Again this project was undertaken with the guys at Gedgers and engineroomapps. Core location and the Mapkit API are used to pinpoint the users location and find their default constituency. Core data is then used to store the list of constituencies and candidates details. The contact feature issues a request to the backend web service, which will forward the provided details onto the candidate. The striking orange buttons and rounded containers are drawn using Quartz 2D.

The semi-interesting part is the way it handles collisions. When Sievehash encounters a collision is makes another hash table smaller than it’s parent. Each new key is dropped through the Seive until an empty spot is found and becomes it’s new home, forming a structure like a Seive.

Similar to most hash tables, when any table reaches the specified load factor all keys will be copied to a new larger table.

Sieve Hash Library: SieveHash.h

Hash test package: HashTests

*** Starting String Test: STL TR1
- Insert Took: 2.751855
- Lookup Took: 2.694130
} Test Took: 8.425282
*** Starting String Test: SieveHash
- Insert Took: 4.447270
- Lookup Took: 2.972444
} Test Took: 10.369791
*** Starting String Test: KHash CPP
- Insert Took: 2.676008
- Lookup Took: 3.056431
} Test Took: 8.704912
*** Starting String Test: Google Dense Hash Test
- Insert Took: 5.109226
- Lookup Took: 4.746739
} Test Took: 12.817609

WARNING: This is not meant for production code, it is for testing purposes only.

Features:

• Themeable UI
• DOM HTML parser
• Save Questions Offline
• Search AND, OR, Phrase, body and title
• FREE!

At present the version available in store is v0.1, which does not include most of the features seen in the screenshots, an update has been submitted and will be available soon. In the meantime you can still download Stack Overflow v0.1 in the app store

• A user will be able to view news content whilst the application is on-line and off-line
• A user will be able to share a news article by e-mail.
• A user will launch the app and be able to read the latest news from The Business Desk
• A user will view a headlines list to choose a full article to view.
• A user can login

Solution

I worked with the team at engineroomapps.com <http://engineroomapps.com> on this project using using agile development techniques and collaboration tools such as basecamp, git and targetprocess. The app front end interface and logic were development by me using objective c and the SDK 3.0 API. Initially the news data was proposed to be supplied using Ruby & activeresource, however the library was eventually discarded due to stability issues. Instead the feed was provided by the web service team in xml format and parsed on the app side using touchxml. For offline viewing data is saved persistently using core data, reachability code is used to display when reading news online or offline.

The business desk app is available FREE in the app store

#include <stdio.h>
#include <time.h>
#include <netinet/in.h>
typedef struct { int ID; char * title; char * link; char * date; int upVotes; int downVotes; void * next; } Article; Article * root; char * getVal(char * query, char * key) { char * str = malloc(1); int match = 0; int pMatch = 0; char * cur = query; while (*cur != '\0') { if (pMatch >= 1 && (*cur == '&' || *cur == '\n' || *cur == ' ')) { break; } else if (pMatch >= 1) { str = realloc(str, pMatch+1); *(str+pMatch-1) = *cur; ++pMatch; } else if (match == strlen(key)) { pMatch = 1; } else if (*cur == key[match]) { ++match; } else { match = 0; } cur++; } if (pMatch >= 1) { str[pMatch-1] = '\0'; return str; } free(str); return NULL; } char from_hex(char ch) { return isdigit(ch) ? ch - '0' : tolower(ch) - 'a' + 10; } char to_hex(char code) { static char hex[] = "0123456789abcdef"; return hex[code & 15]; } char *url_decode(char *str) { char *pstr = str, *buf = malloc(strlen(str) + 1), *pbuf = buf; while (*pstr) { if (*pstr == '%') { if (pstr[1] && pstr[2]) { *pbuf++ = from_hex(pstr[1]) << 4 | from_hex(pstr[2]); pstr += 2; } } else if (*pstr == '+') { *pbuf++ = ' '; } else { *pbuf++ = *pstr; } pstr++; } *pbuf = '\0'; return buf; } void send_headers(FILE *f, int status, char *title, char *extra, char *mime, int length) { char timebuf[128]; fprintf(f, "%s %d %s\r\n", "HTTP/1.0", status, title); fprintf(f, "Server: %s\r\n", "redditserver/1.0"); if (extra) fprintf(f, "%s\r\n", extra); if (mime) fprintf(f, "Content-Type: %s\r\n", mime); if (length >= 0) fprintf(f, "Content-Length: %d\r\n", length); fprintf(f, "Connection: close\r\n"); fprintf(f, "\r\n"); } void reddit(FILE *f) { fprintf(f, "<HTML><HEAD><TITLE>Reddit Clone</TITLE></HEAD>\r\n"); fprintf(f, "<BODY><H1>Submit</H1><form action=\"/\" method=\"get\">Title:<input type=\"text\" name=\"title\" /> Link:<input type=\"text\" name=\"link\" /><input type=\"submit\" value=\"Submit\" /></form>\r\n"); if (root) { fprintf(f, "<h1>Articles</h1>"); Article * cur = root; while (cur != NULL) { fprintf(f, "<p><font size=\"5\">%d<b><a href=\"/?up=%d\">&uarr</b></font><a href=\"%s\">%s</a><br /><font size=\"5\">&nbsp;&nbsp;<b><a href=\"/?down=%d\">&darr</a></b></font>%s -- %s</p>", cur->upVotes - cur->downVotes, cur->ID, cur->link, cur->title, cur->ID, cur->link, cur->date); cur = cur->next; } }fprintf(f, "</BODY></HTML>\r\n"); } int fsize(FILE * f) { fseek(f, 0, SEEK_END); int size = ftell(f); fseek(f, 0, SEEK_SET); return size; } int main(int argc, char *argv[]) { int sock; int port = 1337; struct sockaddr_in sin; sock = socket(AF_INET, SOCK_STREAM, 0); sin.sin_family = AF_INET; sin.sin_addr.s_addr = INADDR_ANY; sin.sin_port = htons(port); while (bind(sock, (struct sockaddr *) &sin, sizeof(sin)) < 0) { printf("Failed bind\n"); sleep(2); } listen(sock, 5); printf("HTTP server listening on port %d\n", port); root = NULL; while (1) { int s; int size; int hsize; char * buff; FILE * t; FILE * ht; FILE * f; s = accept(sock, NULL, NULL); if (s < 0) break; char * header = calloc(255, 1); size = read(s, header, 255); char * titleEnc = getVal(header, "title"); char * linkEnc = getVal(header, "link"); if (titleEnc && linkEnc) { char * title = url_decode(titleEnc); char * link =  url_decode(linkEnc); free(linkEnc); free(titleEnc); printf("Title: %s -- Link: %s\n", title, link); char  * s = malloc(30); size_t i; struct tm tim; time_t now; now = time(NULL); tim = *(localtime(&now)); i = strftime(s,30,"%b %d, %Y; %H:%M:%S\n",&tim); Article * new = malloc(sizeof(Article)); new->title = title; new->link = link; new->next = NULL; new->date = s; new->upVotes = 0; new->downVotes = 0; if (!root) { root = new; new->ID = 0; } else { int dupe = 0; Article * cur = root; Article * prev = NULL; while (cur != NULL) { if (strcmp(cur->title, new->title) == 0 || strcmp(cur->link, new->link) == 0) { dupe = 1; } prev = cur; cur = cur->next; } if (dupe == 0) { new->ID = prev->ID + 1; prev->next = new; } else free(new); } } char * upID = getVal(header, "up"); if (upID) { int ID = atoi(upID); Article * cur = root; while (cur != NULL) { if (cur->ID == ID) { cur->upVotes++; break; } cur = cur->next; } } char * dID = getVal(header, "down"); if (dID) { int ID = atoi(dID); Article * cur = root;  while (cur != NULL) { if (cur->ID == ID) { cur->downVotes++; break; } cur = cur->next; } } t = tmpfile(); ht = tmpfile(); reddit(t); size = fsize(t); send_headers(ht, 200, "Ok", NULL, "text/html", size); hsize = fsize(ht); buff = malloc(hsize); fread(buff, 1, hsize, ht); write(s,buff,hsize); free(buff); buff = malloc(size); fread(buff, 1, size, t); write(s,buff,size); free(buff); fclose(t); } }

$ gcc reddit.c -o reddit
$ ./reddit
HTTP server listening on port 1337 — http://localhost:1337/

reddit.c

For example if were creating a news application, we want to be able to import news in the background and display updates to the user with no interruption of the GUI. The task can be divided into several stages:

1. Download the xml feed with the latest news
2. Parse the feed
3. Insert the articles into core data
4. Notify the UI and refresh the display.

We already have our core data API defined. A simple method to retrieve all the articles and a method to add a new article.
DataSource.h

@interface DataSource : NSObject { }
-(NSArray*)getNewsFor:(Region*)region;
-(void)addArticle:(Article*)article forRegion:(Region*)region;
@end
}

Now suppose we want to the web service to import the latest articles. We might define our implementation something like this:
WebService.h

@interface WebService : NSObject {
	id delegate;
	LocalDataSource * source;
}
 
@property(nonatomic, retain) id delegate;
@property(nonatomic, retain) LocalDataSource * source;
-(void)importNewsForRegion:(Region*)region;
 
@end

Our implementation of importNewsForRegion would look something like this:

WebService.m

-(void)importNewsForRegion:(Region*)region
{
	//Perform in background if called from main
	 if ([NSThread currentThread] == [NSThread mainThread])
	{
		[self performSelectorInBackground:@selector(importNewsForRegion:) withObject:region];
		 return;
	}
 
	//Setup pool
	 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 
	 NSArray * articles = [XML parseArticleFeed:region.feedURL]; //Not safe 1.
	 for (Article * article in articles)
	{
		[source addArticle:article forRegion:region]; //Not safe 2.
	}
 
	[delegate finishedImport]; //Not safe 3.
	[pool drain];
}

However this because importNewsForRegion is running in a separate thread this is unsafe and will likely cause core data to crash or corrupt our database.

1. The region passed to to importNews has likely come from a core data context which was constructed on the main thread. Even though were not even altering the region directly with core data it’s not safe to even read the feedURL, because every operation can trigger faulting.
2. When we instruct the source to add an article it will use the main threads context, this is fine when we are in the main thread, but in a background thread we need to specify our own context.
3. Not related to core data, but when we notify the delegate it will likely perform UI updates which are not safe to perform in a background thread. we need to ensure the delegate only received notifications on the main thread.

To make our program thread safe we first need to make some small alterations to our API.

DataSource.h

@interface DataSource : NSObject { }
-(NSArray*)getNewsFor:(Region*)region;
-(NSArray*)getNewsFor:(Region*)region context:(NSManagedObjectContext*)context;
 
-(void)addArticle:(Article*)article forRegion:(Region*)region;
-(void)addArticle:(Article*)article forRegion:(Region*)region context:(NSManagedObjectContext*)context;
@end
}

In our data source we specify two more methods which allow us to provide a context for the method to use. All our queries should be updated to only use the provided context. The original methods that don’t specify a context should call the newly implemented method with the default context, e.g.

-(void)addArticle:(Article*)article forRegion:(Region*)region
{
        [self addArticle:article forRegion:region context:mainThreadContext];
}

Only when we are using core data in a background thread do we need to use the newly added methods. So we can now update our WebService.m:

-(void)importNewsForRegion:(Region*)unsafeRegion
{
	//Perform in background if called from main
	 if ([NSThread currentThread] == [NSThread mainThread])
	{
		[self performSelectorInBackground:@selector(importNewsForRegion:) withObject: unsafeRegion];
		 return;
	}
 
	//Setup pool
	 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 
	//Create a new context just for this thread
	NSManagedObjectContext * managedObjectContext = [[NSManagedObjectContext alloc] init];
	[managedObjectContext setPersistentStoreCoordinator:  [source persistentStoreCoordinator]];
 
        //Create a new region which is safe to use in this thread
	Region * region = (Region*)[managedObjectContext existingObjectWithID:[unsafeRegion objectID] error:nil];
 
	 NSArray * articles = [XML parseArticleFeed:region.feedURL];
	 for (Article * article in articles)
	{
               //Ensure we provide the context for the source to use
		[source addArticle:article forRegion:region context:managedObjectContext];
	}
 
	//Save changes and close the new context
	[managedObjectContext save:&error];
	[managedObjectContext release];
 
	[delegate performSelectorOnMainThread:@selector(finishedImport) withObject:nil waitUntilDone:NO];
	[pool drain];
}

As you can see we crate a new context using out shared persistentStoreCoordinator, we ensure that anytime we touch core data from this thread we are using this context. The also means that we have to create a new region which belongs to this context, and we do this with the existingObjectWithID method and using the [unsafeRegion objectID]. Finally we ensure that the delegate receives the notification on the main thread.

for more information about threading in core data see:

http://developer.apple.com/Mac/library/documentation/Cocoa/Conceptual/CoreData/Articles/cdMultiThreading.html

Download the latest source from:

http://code.google.com/p/cocos2d-iphone/downloads/list

I recommend you stick with the stable releases, unless there is a specific feature your require from a new version.

Unzip the folder and the template installation script:

$ ./install_template.sh

This will make a series of cocos-2d templates available from XCode.  Launch/restart xcode and choose File->New Project->cocos2d Application build and run the new application in the simulator and it should look something like this:

Were going to build on this template to add a main menu

First download the test image and add it to the new xcode project (Make sure it is copied into the application directory)

Create a new class name MenuScene and add the following code to the header file:

#import
#import "cocos2d.h"
 
@interface MenuScene : Scene
{
 
}
 
@end
 
@interface MenuLayer : Layer
{
}
 
-(void)startGame: (id)sender;
-(void)help: (id)sender;
 
@end

The add the following to the .m file:

#import "MenuScene"
 
@implementation MenuScene
 
- (id) init
{
    self = [super init];
    if (self != nil) {
        Sprite * bg = [Sprite spriteWithFile:@"MainMenuBackground.png"];
        [bg setPosition:ccp(160, 240)];
        [self addChild:bg z:0];
        [self addChild:[MenuLayer node] z:1];
    }
    return self;
}
 
@end
 
@implementation MenuLayer
 
- (id) init
{
    self = [super init];
    if (self != nil)
	{
        [MenuItemFont setFontSize:24];
        [MenuItemFont setFontName:@"Helvetica"];
 
        MenuItem *start = [MenuItemFont itemFromString:@"Start Game"
												target:self
											  selector:@selector(startGame:)];
 
        MenuItem *help = [MenuItemFont itemFromString:@"Help"
											   target:self
											 selector:@selector(help:)];
 
        Menu *menu = [Menu menuWithItems:start, help, nil];
		menu.color = ccc3(0, 0, 0);
 
        [menu alignItemsVertically];
        [self addChild:menu];
    }
    return self;
}
 
-(void)startGame: (id)sender
{
    NSLog(@"start game");
}
 
-(void)help: (id)sender {
    NSLog(@"help");
}
 
@end

Finally modify the app delegate (CocosTestAppDelegate.m) to include MenuScene.h

#import "MainMenuScene.h"

and replace the line:

[[Director sharedDirector] runWithScene: [HelloWorld scene]];

with:

[[Director sharedDirector] runWithScene: [MenuScene node]];

also remove the line:

[[Director sharedDirector] setDeviceOrientation:CCDeviceOrientationLandscapeLeft];

Compile and run the project and you should end up with a menu and two clickable buttons:

• Graphics / Html have never been my strong point. Sure I can cut and paste from other designs and cobble together something which resembles a web page, but they always look just that, cobbled together.
• It doesn’t get much traffic or provide much business value at present and hence I don’t want to have to pay a designer.

I had previously used iWeb and then up until recently rapidweaver, these applications are fine up to a point, but soon there lack of advanced features and template editing becomes apparent.  Between an application like iWeb and designing the site from scratch we have content management systems (CMS), the most popular being Drupal, Joomla and wordpress.

I had heard good reviews of Drupal before so this was my first port of call. I won’t go into detail about the setup, but it was overall fairly straight forward, however after that things went downhill. The admin panel was confusing and slow, I spent several hours trying to get the sites navigation and content to resemble something how I wanted. It seemed like every theme I tried ended up looking like the same boxy layout, you could immediately tell the site was using drupal. The themes were poor quality, difficult to modify and modules were complicated to install. After my drupal experience I gave up on CMS for a while.

Today I decided to give wordpress a shot. Since I already had php setup, Installation really was a case on unpacking the zip file and placing it in the apache home directory. I immediately went to install a new template. Wordpress features an automatic template installation system, however this is where I hit my first stumbling block. Wordpress kept asking for my ftp information, however a quick google search revealed my file permissions were wrong.

The following command did the trick: sudo chmod -R 777 /Path/To/Wordpress

Other than that templates where easy to install and I had found several decent looking ones in a few minutes. The next task was to add a contact page, unfortunatly wordpress doesn’t come with one as standard however the plugin “Contact Form 7″ was easy to install without leaving the admin interface. Even the more advanced task of separating the wordpress blog into two different pages (see The Loop) could be done without leaving the admin interface.

Overall I have been extremely impressed so, maybe I’ll run into customisation limitations again later, however at the moment I can’t praise wordpress enough.

When the device is connected to a cellular network, iVersion does not load its contents.  After the user enters the URL (http://svn.collab.net/repos/svn/trunk/) and taps “connect,” an error message is received.

Apparently the error message is not clear enough or something, anyway this is not a rant, this is what apple recommends.

Please take a look at the Reachability iPhone program sample which demonstrates the use of the System Configuration Reachability API to detect the absence of WiFi and Wireless Wide Area Network (WWAN) services. Your application can then take appropriate action at the first point where network services are required.

The sample code can be found on Apple developer site, however the two file we are interested in are:

Download the Reachability Code:
Reachability.h

Reachability.m

How to use:
Lets say you have a simple UILabel which you want to update with either “(Offline)” or “(Online)” depending on whether the network is reachable. Your view controller would be defined something like this:

@interface MyStatusView : UIViewController
{
	UILabel * statusLabel;
}
 
@property(nonatomic, assign) IBOutlet UILabel * statusLabel;
 
- (void)reachabilityChanged:(NSNotification *)note;
- (void)updateStatus;
 
@end

Then we add the following code to the view controller .m file:

-(void)viewWillAppear:(BOOL)animated
{
	self.reachability = [Reachability reachabilityWithHostName:@"google.com"];
	[reachability startNotifer];
 
	[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:@"kNetworkReachabilityChangedNotification" object:nil];
 
	[self updateStatus];
}
 
-(void)viewWillDisappear:(BOOL)animated
{
	self.reachability = nil;
	[[NSNotificationCenter defaultCenter] removeObserver:self];
}
 
-(void)reachabilityChanged:(NSNotification*)notification
{
	[self updateStatus];
}
 
-(void)updateStatus
{
	NSLog(@"Reachability changed");
 
	if ([reachability currentReachabilityStatus] == NotReachable)
	{
		statusLabel.text = @"(Offline)";
	}
	else
	{
		statusLabel.text = @"(Online)";
	}
}

I think it’s fairly self explanatory. Basically when the view appears the reachability class is created and started using startNotifier. Then we hook in our reachabilityChanged: method into the notification centre, so it is automatically called when the network status changes. reachabilityChanged: calls updateStatus which simply changes our label depending on the connectivity.

First we create a new class which has a view which will be loaded from a nib, a thread condition to lock the calling thread and two NSString fields to store the result and the string of the button which was clicked.

@interface MessagePrompt : NSObject
{
 
UIView * view;
NSCondition * promptCondition;
NSString * clickedButton Text;
NSString * result;
{
@end

Our new prompt method can be called from the thread which needs to be locked, it will subsequently call UIKit on the main thread.

+(id)newPrompt:(MessagePrompt*)prompt
{
 
     if ([NSThread currentThread] == [NSThread mainThread])
    {
          printf("Should not be called by Main thread\n");
          return nil;
    }
 
     prompt.promptCondition = [[[NSCondition alloc] init] autorelease];
 
    [prompt performSelectorOnMainThread:@selector(prompt:) withObject:view waitUntilDone:NO];
    [prompt.promptCondition wait];
 
    return prompt;
}

This method is called by +(id)NewPrompt and displays a prompt in our window. It also adds targets to each UIButton to receive user actions.

-(void)prompt:(UIView*)inView
{
     NSArray * nib = [[NSBundle mainBundle] loadNibNamed:@"MyPromptView" owner:self options:nil];
     inView = [nib objectAtIndex:0];	
 
     NSArray * subviews = [self.view subviews];
     for (UIView * cview in subviews)
    {
          if ([cview isKindOfClass:[UIButton class]])
          {
               UIButton * button = (UIButton*)cview;
                [button addTarget:self action:@selector(clicked:) forControlEvents:UIControlEventTouchDown];
          }
    }
 
    [inView.superview addSubview:view];
}

This is called when a user clicks a button, it finds the value field and retreives and stores the value in self.message. The prompt condition is then signalled which causes the calling thread to continue running.

-(IBAction)clicked:(UIButton*)sender
{
     self.clickedButton = sender.currentTitle;
 
     UITextView * text = [iVersionAppDelegate findSubViewOfKind:self.view class:[UITextView class]];
     if (text)
    {
         self.message = text.text;
    }
 
    [self.view removeFromSuperview];
     self.view = nil;
 
    [promptCondition signal];
}
 
@end

Usage

/* Called when svn requires a log message */
svn_error_t *
iversion_svn_cl__get_log_message(const char **log_msg,
const char **tmp_file,
const apr_array_header_t *commit_items,
void *baton,
apr_pool_t *pool)
{
 
CommitLogMessagePrompt * prompt = [CommitLogMessagePrompt newPrompt];
 
    /* Clicked Continue */
     if ([prompt.clickedButton isEqualToString:@"Continue"])
    {
        *log_msg = [prompt.message UTF8String];
         return SVN_NO_ERROR;
    }
 
     return svn_error_create(SVN_ERR_CANCELLED, NULL, _("Delete Cancelled"));
}

#include "FileSystemMonitor.h"
 
//Setup the monitor
FileSystemMonitor * monitor = [[FileSystemMonitor alloc] init];
monitor.delegate = self;
[monitor monitorPath:@"/"];
 
//...In your delegate class
-(void)nodeWasCreatedAt:(NSString*)path
{
     printf("Created %s\n", [path UTF8String]);
}
 
-(void)nodeWasDeletedAt:(NSString*)path
{
    printf("Deleted %s\n", [path UTF8String]);
}
 
-(void)fileSizeDidchange:(NSString*)path bytes:(size_t)difference
{
     printf("file Added %ul bytes\n", difference);
}

Notes:

• Can monitor for Deleted files, Created Files and File Size Changes
• On an iPhone 3GS it is able to monitor the entire SVN 1.6 source tree and the iVersion source tree (total 11,050 File/Directories) in an execution time of 12s. Due to the low thread priority and the fact that the majority of execution time is IO it does not cause much/any slow down to the UI. However there is still room for improvement.

Download:

FileSystemMonitor.h

FileSystemMonitor.m

FileMonitorDelegateProtocol.h

In the inner parsing loop I have been using the standard NSMutableArray to keep track of various objects and tokens. Objective C message passing is of course an order of times slower than a C function call, even if purely for the fact that they can’t be inlined. A great article that explains more about the objective c runtime an be found on the cocoa samurai blog

So I decided to drop down to a dynamic array using plain C. However even though I’m sure dynamic arrays have been implement thousands of times I couldn’t seem to find any simple implementations.

//** Usage
//Create an array with capacity 2
CArray * array = CArrayInit(2);
 
//Add two buckets
CArrayAdd(array, "test");
CArrayAdd(array, "another test");
 
//Add another and it will resize accordingly
CArrayAdd(array, "yet another");
 
//Print All
for (int ii = 0; ii < array->count; ++ii)
{
        const char * buffer = CArrayObjectAtIndex(array, ii);
        printf("Index: %d - %s\n", ii, buffer);
}

Download:

CArray.h

CArray.c

Notes:
The following test function usually reports about 5x faster than NSMutableArray which I think is a credit to how efficient the Objective C library and messaging system really is considering all the things your missing out on (exceptions, null pointers etc)

void CArrayTestRoutine()
{
 
    CArray * array = CArrayInit(0);
 
    NSTimeInterval start = [[NSDate date] timeIntervalSince1970];
    NSString * test;
 
    for (int ii = 0; ii < 10000000; ++ii)
    {
        CArrayAdd(array, @"test");
        test = CArrayObjectAtIndex(array, CArrayCount(array)-1);
    }
 
     CArrayRemoveObjectAtIndex(array, 0);
 
     NSTimeInterval end = [[NSDate date] timeIntervalSince1970];
     printf("CArray 100,000,000 Elements took %fs\n", end-start);
 
     NSMutableArray * nsarray = [[NSMutableArray alloc] initWithCapacity:0];
     start = [[NSDate date] timeIntervalSince1970];
     NSString * string;
 
     for (int ii = 0; ii < 10000000; ++ii)
    {
        [nsarray addObject:@"test"];
        string = [nsarray objectAtIndex:[nsarray count]-1];
    }
 
    [nsarray removeObjectAtIndex:0];
 
     end = [[NSDate date] timeIntervalSince1970];
    [nsarray release];
     printf("NSMutableArray 100,000,000 Elements took %fs\n", end-start);
 
     printf("%s\n", [string UTF8String]);
     printf("%s\n", [test UTF8String]);
     CArrayDestroy(array);
 
}

iVersion uses the open source subversion 1.6 client library, written in plain C, with an Objective C wrapper for simpler interfacing with the Objective C UI. Using an objective C Wrapper the client can easily be abstracted to work with other version control protocols. In the future git, mercurialand bazaar support maybe included.

Features

• Multi-threaded non-locking ui
• OpenSSL support for https:// and svn+ssh:// connections
• svn commands: list, info, cat,
• Browse Directories
• View Commit Logs
• View file Info
• Bookmarks, History & Directory Cache through NSUserDefaults

** Commit Support
Subversion does not allow commiting of a single file without a working copy of the previous directory. A work around for this has been found and commit support should be available in a future version.

1. Loads an XML file;
2. Presents the XML data in an a table that can be sorted by each column;
3. Enables custom views of data, i.e., show all columns or only some;
4. Exports updated information back into the XML format;
5. Has an “FTP Widget” that can upload images to a server.

Solution:
As per the clients specification the application was written using primarily Objective C, with Xcode as the development IDE. The UI is designed to be powerful and customizable. Profiles can be created to customize the view of the XML data. The Main window is split between an image view and a table view, which the user can adjust and hide if necessary, which is smoothly animated. Side drawers are used to display additional Options to the user.

XML parsing is handled using Cocoa’s bundled NSXMLParser using the format supplied by the client. The XML file can be imported, searched and exported using a tabular style layout. Fields can be edited, copied or deleted using single or multiple selections. The XML file can be uploaded to the site from within the app using NSURLConnection and http post.

Initially the possibility of using an existing Objective C Ftp library, such as Connection kit was explored, as well as the possibility of interfacing directly with an existing Mac ftp client such as Cyberduck. However the final solution was to write a lightweight ftp client using C Sockets with an Objective C API wrapper. The result is the user can quickly and easily upload and download images directly from the program, without any external dependancies.

Mosiaco has been tested throughly with Xcode’s Leaks and GNU gdb and is stable and leak free without garbage collection.

“ zootreeves was exactly the kind of provider I was looking for in this collaboration: he knew exactly how to take my vision for the app and make it a reality. In addition, he always brought alternative solutions and new ideas to the table. The final product is above and beyond what I had hoped to create. He was a thorough pleasure to work with and I would highly recommend him to anyone looking for a Mac OS X app developer. Timothy Allen President & Creative Director Hypergolica, Inc. www.hypergolica.net”

For more information regarding the Mosaico web gallery desktop software or if you are interested in finding an all in one solution for your online web gallery hosting please contact Mosaico or Hypergolica

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