SBJson和NSData

Question

我正在从quizlet.com获取数据，对于简单的代码，它工作得很好：

-(void) grabbQuizletWithUrl:(NSURL*)requstURL {

     NSString *dataString = [NSString stringWithContentsOfURL:requestURL encoding:NSUTF8StringEncoding error:&error]; 

     NSDictionary *dict = [dataString JSONValue];
}

但是我需要使用NSURLConnection来启动和停止活动指示器。我在努力

-(void) grabbQuizletWithUrl:(NSURL*)requstURL {

    NSURLRequest *quizletRequest = [[NSURLRequest alloc] initWithURL:requestURL];
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:quizletRequest
                                                          delegate:self];
    [connection release];
    [quizletRequest release];

}

// and getting data in delegate method:



- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

    [self.activityIndicator stopAnimating];

    NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    NSDictionary *dict = [dataString JSONValue];

}

我收到了这样的消息：

2377:707 -JSONValue失败。错误是:意外的输入结束

2377:707 -JSONValue失败。错误是:令牌的开始非法。

2377:707 -JSONValue失败。错误是:标记%d的开始非法

Answer 1

在- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;中，您应该只将接收到的数据附加到先前存储的数据中，因为您只获得了响应的一部分，即：

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    // someNSMutableDataIVar is an ivar to store the data in
    [someNSMutableDataIVar appendData:data];
}

然后，在另一个名为- (void)connectionDidFinishLoading:(NSURLConnection *)connection;的委托方法中，您应该处理数据。

-(void)connectionDidFinishLoading:(NSURLConnection *)connection {
    // the connection finished loading all data, process...
    [self.activityIndicator stopAnimating];
    NSString *dataString = [[NSString alloc] 
                            initWithData:someNSMutableDataIVar
                                encoding:NSUTF8StringEncoding];
    NSDictionary *dict = [dataString JSONValue];
}

苹果公司的URL Loading System Programming Guide中详细描述了异步网址加载系统。

希望这能有所帮助！