Backend-Kommunikation

HTTP(S)-Kommunikation

• NSData repräsentiert Binärdaten und erlaubt auch das Laden von Daten von URLs:

  NSURL* url = [NSURL URLWithString:@"http://www.google.de/"];
  NSError* error = nil;
  NSData* data = [NSData dataWithContentsOfURL:url options:0 error:&error];
  if (error) {
      NSLog(@"Error %@, %@", error, [error userInfo]);
      // ... handle error
  }
  else {
      NSLog(@"Loaded data: %@", data);
  }
  

• Alternativ: [NSString stringWithContentsOfURL:encoding:error]

• NSURLConnection erlaubt die Ausführung von asynchronen Requests

Beispiel: Asynchrone Requests mit NSURLConnection 1/2

- (void) loadData {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    NSURL* url = [NSURL URLWithString:@"http://www.example.com/"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    self.connection =
        [[[NSURLConnection alloc] initWithRequest:request delegate:self] autorelease];
}

#pragma mark NSURLConnection delegate methods

- (void) connection:(NSURLConnection *)con didReceiveResponse:(NSURLResponse *)resp {
    self.data = [NSMutableData data];
}

Beispiel: Asynchrone Requests mit NSURLConnection 2/2

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)aData {
    [self.data appendData:aData];
}

- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    NSLog(@"URL connection failed with %@, %@", error, [error userInfo]);
    self.data = nil;
    self.connection = nil;
}

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    // parse data here
    self.data = nil;
    self.connection = nil;
}

TouchJSON

• TouchJSON ist ein Objective-C JSON-Parser und -Generator.

• JSON parsen:

  #import "CJSONDeserializer.h" 
  
  NSDictionary *dictionary = [[CJSONDeserializer deserializer]
      deserializeAsDictionary:jsonData error:&error];
  

• JSON generieren:

  #import "CJSONSerializer.h" 
  
  NSDictionary *dictionary = [NSDictionary dictionaryWithObject:@"value" forKey:@"key"];
  NSString *jsonString = [[CJSONSerializer serializer] serializeObject:dictionary];
  

Alternativen zur Kommunikation / Serialisierung

• NSXmlParser: SAX-XML-Parser (Bestandteil vom iPhone-SDK)
• TouchXML: DOM-XML-Parser
• Protocol Buffers: Nachrichten-/Protokollbasiertes Serialisierungsformat
• Connection Kit: Dateitransfer via HTTP, FTP, SFTP, WebDAV, .Mac und zu Amazon S3

Reachability

• SCNetworkReachability erlaubt die Abfrage und Beobachtung der Netzwerk-Erreichbarkeit des iPhones
• Beantwortet die Frage “Können Pakete das iPhone verlassen?”
• Siehe Beispielanwendung ”Reachability”

Tipps & Tricks: Webserver ad hoc starten

cd webroot/
python /cd/toolbox/scripts/www_here.py

Weiterführende Informationen 1/2

• TouchJSON Howto http://code.google.com/p/touchcode/wiki/TouchJSONHowTo
• TouchXML http://code.google.com/p/touchcode/wiki/TouchXML
• Building an Advanced RSS reader using TouchXML: http://dblog.com.au/general/iphone-sdk-tutorial-building-an-advanced-rss-reader-using-touchxml-part-1/
• Protocol Buffers: http://code.google.com/p/protobuf/
• Objective-C Protocol Buffers for OSX and the iPhone: http://code.google.com/p/metasyntactic/wiki/ProtocolBuffers
• iPhoneWebServicesClient: Showcase for transport formats and libraries: http://github.com/akosma/iPhoneWebServicesClient

Weiterführende Informationen 2/2

• HTTPRiot - Easily Consume REST Resources on the iPhone and OS X: http://alternateidea.com/blog/articles/2009/7/11/introducing-httpriot-easily-consume-rest-resources-on-the-iphone-and-os-x
• Connection Kit: http://opensource.utr-software.com/connection/