Fuer meine iPad app hab ich mir mit Django nen backend geschrieben. Das hier ist eine abstrakte Klasse, die ich mir gebaut hab um das backend anzusprechen.

request.m

//
//  Request.m
//  IronMon
//
//  Created by Marco Lamina on 29.09.11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Request.h"
#import "ASIHTTPRequest.h"
#import "ASIFormDataRequest.h"

@implementation Request

@synthesize url, params, method, postParams, timeoutInSeconds;

- (id)init
{
    self = [super init];
    if (self) {
        adapter = [SBJsonStreamParserAdapter new];        
        adapter.delegate = self;
        parser = [SBJsonStreamParser new];
        parser.delegate = adapter;
        parser.supportMultipleDocuments = YES;
        self.method = @"GET";
        self.params = [NSMutableDictionary new];
        self.postParams = [NSMutableDictionary new];
        self.timeoutInSeconds = 0;
    }
    
    return self;
}

- (id) initWithUrl: (NSString*) requestUrl {
    self = [self init];
    if (self) {
        self.url = requestUrl;
    }
    return self;
}

- (void) fire: (NSObject<RequestDelegate>*) del {
    // Fetch all available machines
    
    delegate = [del retain];
    
    
    
    // Add parameters to URL
    if ([self.params count]>0) {
        self.url = [NSString stringWithFormat:@"%@?", self.url];
        for (NSString* key in [self.params allKeys]) {
            NSString* value = @"";
            if ([key isEqualToString:@"limit_attributes"])
                for (NSString* filter in ((NSArray*)[self.params objectForKey: key]))
                    value = [NSString stringWithFormat:@"%@,%@", value, filter];
            else
                value = [self.params objectForKey:key];
            self.url = [NSString stringWithFormat:@"%@&%@=%@", self.url, key, value];
        }
            
                
        
            
    }
    
    NSURL *requestUrl = [NSURL URLWithString: self.url];
    
    
    
    
    
    if ([self.method isEqualToString:@"POST"]) {
        
        ASIFormDataRequest* request = [ASIFormDataRequest requestWithURL: requestUrl];
        
        // Enable gzip compression
        request.shouldWaitToInflateCompressedResponses = NO;
        for (NSString* key in [self.postParams allKeys])
            [request setPostValue: [self.postParams valueForKey: key] forKey: key];
        
        [request setDelegate:self];
        [request setTimeOutSeconds: self.timeoutInSeconds];
        [request startAsynchronous];
        
    } else {
        ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:requestUrl];
        // Enable gzip compression
        request.shouldWaitToInflateCompressedResponses = NO;
        [request setDelegate:self];
        [request setTimeOutSeconds: self.timeoutInSeconds];
        [request startAsynchronous];
    }
    


}

- (void)requestFinished:(ASIHTTPRequest *)request
{
    // Use when fetching text data
    
    NSData *responseString = [((ASIFormDataRequest*)request) responseData];    
    
    SBJsonStreamParserStatus status = [parser parse:responseString];
    
    if (status==SBJsonStreamParserError) {
        // parser error
        [delegate requestFailed: parser.error];
        [delegate release];
    } else if (status==SBJsonStreamParserWaitingForData) {
        // waiting for data
    }
    
}

- (void)requestFailed:(ASIHTTPRequest *)request
{
    NSError *error = [request error];
    NSLog(@"Request Error: %@: %@ ", [error localizedDescription], [error localizedFailureReason]);
    [delegate requestFailed: [error localizedDescription]];
    [delegate release];
}


#pragma mark SBJsonStreamParserAdapterDelegate methods

-(void)parser:(SBJsonStreamParser*)parser foundArray:(NSArray *)array {
    
    NSArray* models = [self parseJSONArray: array];
    [delegate requestFinished: models];
    [delegate release];
    
    
}

-(void)parser:(SBJsonStreamParser*)parser foundObject:(NSDictionary *)dict {
    
}

- (NSArray*) parseJSONArray: (NSArray*) array {
    // Abstract method
    @throw [NSException 
            exceptionWithName:NSInternalInconsistencyException 
            reason:[NSString stringWithFormat:@"You must override %@ in a subclass", NSStringFromSelector(_cmd)] 
            userInfo:nil];
}

- (void) limit: (int) num {
    [self.params 
        setValue:[NSString stringWithFormat:@"%d", num] 
        forKey:@"limit"];
}

- (void) latest: (int) num {
    [self.params 
     setValue:[NSString stringWithFormat:@"%d", num] 
     forKey:@"latest"];
}

- (void) addFilterForModel: (NSString*) model attribute: (NSString*) attribute {
    if (![self.params objectForKey: @"limit_attributes"])
        [self.params setValue: [NSMutableArray new] forKey:@"limit_attributes"];
    NSMutableArray* filters = [self.params objectForKey:@"limit_attributes"];
    [filters addObject: [NSString stringWithFormat:@"%@__%@", model, attribute]];
}

- (void) filterFrom: (NSDate*) startTime to: (NSDate*) endTime {
    NSDateFormatter* formatter = [[NSDateFormatter new] autorelease];
    formatter.dateFormat = @"YYYY-MM-dd'T'HH:mm:ss";
    
    [self.params 
     setValue:[NSString stringWithFormat:@"%@,%@", [formatter stringFromDate: startTime], [formatter stringFromDate: endTime]] 
     forKey:@"date"];
}

-(void) dealloc {
    //[params release];
    [parser release];
    [adapter release];
    [self.method release];
    [self.params release];
    [self.url release];
    [self.postParams release];
    [super dealloc];
}

@end