如果需要委托函数，如何直接返回 NSURLConnection 加载的数据？

Question

简短说明我想要做什么：我正在使用 NSURLConnection 连接到 SSL 网页，这是我的 API。服务器证书是自签名证书，因此您必须接受它，例如在 Web 浏览器中。我在 Stack Overflow 上找到了一个解决方案，如何解决这个问题（如何使用 NSURLConnection 与 SSL 连接以获得不受信任的证书？）

因此我添加了 NSURLConnection 委托以使用“didReceiveAuthenticationChallenge”等方法。因此，我无法使用它：

NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];

因为在这种情况下不可能使用委托函数。我的问题如下：我需要一个如下所示的函数：

- (NSDictionary *)getData :  (NSArray *)parameter {
    [...|
    NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; 
    [...]
    return myDictionary; 
}

如何使用它返回 NSDictionary？据您所知，现在调用 NSURLConnection 的委托函数，并且此时响应不可用。问题是视图控制器依赖于这个响应，所以我需要直接返回字典...有人知道这个问题的解决方案吗？回调函数怎么样？

Answer 1

好的，我已经找到了解决方案。在 Objective-C 中使用块是一件非常好的事情。

首先，您必须向 NSURLRequest 和 NSURL 添加一些方法：

@implementation NSURLRequest (URLFetcher)

- (void)fetchDataWithResponseBlock:(void (^)(FetchResponse *response))block {
    FetchResponse *response = [[FetchResponse alloc] initWithBlock:block];
    [[NSURLConnection connectionWithRequest:self delegate:response] start];
    [response release];
}

@end

@implementation NSURL (URLFetcher)

- (void)fetchDataWithResponseBlock:(void (^)(FetchResponse *response))block {
    [[NSURLRequest requestWithURL:self] fetchDataWithResponseBlock:block];
}

@end

而不仅仅是实现以下类：

@implementation FetchResponse

- (id)initWithBlock:(void(^)(FetchResponse *response))block {
    if ((self = [super init])) {
        _block = [block copy];
    }
    return self;
}

- (NSData *)data {
    return _data;
}

- (NSURLResponse *)response {
    return _response;
}

- (NSError *)error {
    return _error;
}

- (NSInteger)statusCode {

    if ([_response isKindOfClass:[NSHTTPURLResponse class]]) return [(NSHTTPURLResponse *)_response statusCode];

    return 0;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

    _response = response; 

}

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

    if (!_data) _data = [[NSMutableData alloc] init];

    [_data appendData:data];

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    _block(self);

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

    _error = error;
    _block(self);

}

现在您可以执行以下某种回调函数：

NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://..."];

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setValue:@"application/json" forHTTPHeaderField:@"accept"];

[request fetchDataWithResponseBlock:^(FetchResponse *response) {

    if (response.error || response.statusCode != 200) 
        NSLog(@"Error: %@", response.error); 

    else {

        //use response.data
    }

}];

在这里您可以找到 ICNH 的原始德语解决方案： 异步 I/O mit Bloecken

非常感谢您！

Answer 2

我的建议是对 NSURLConnection 使用一些其他委托方法，例如 connection:didReceiveResponse: 或 connection:didReceiveData:。您可能应该像这样保留使用设置：

@interface MyClass : NSObject {
…
    NSMutableData *responseData;   
}
…
@end

- (void)startConnection {
    NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:request delegate:self];
    if (theConnection) {
        responseData = [[NSMutableData data] retain];
    } else {
        // connection failed
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    // connection could have been redirected, reset the data
    [responseData setLength:0];
}

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

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    // connection is done, do what you want
    ………
    // don't leak the connection or the response when you are done with them
    [connection release];
    [responseData release];
}
// for your authentication challenge
- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace (NSURLProtectionSpace *)protectionSpace {
    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
}

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
    if ([trustedHosts containsObject:challenge.protectionSpace.host])
      [challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];

    [challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
}