Swizzle of NSURLConnection sendAsynchronous:request:queue:co

我已经创建了NSURLConnection和NSURLSession类别来交换，因此我将在运行时拦截呼叫并收集网络信息。除了使用NSURLConnection的静态类方法外，大多数情况下一切都很好。

sendAsynchronousRequest:queue:completionHandler:
sendSynchronousRequest:returningResponse:error:

这两个静态方法在我的混合中不服从，在调试时，我看到方法实现交换像我混合的其他方法一样正确地发生。下面是我的代码，类似于我对其他方法所做的，似乎工作得很好。

typedef void (^SendAsynchronousCompletionHandlerBlock)(NSURLResponse*, NSData*, NSError*);
static void (*OriginalNSURLConnectionSendAsynchronousRequestQueueCompletionHandler)(id, SEL, NSURLRequest*, NSOperationQueue*, SendAsynchronousCompletionHandlerBlock);
static NSData* (*OriginalNSURLConnectionSendSynchronousRequestReturningResponseError)(id, SEL, NSURLRequest*, NSURLResponse**, NSError**);
static void MyNSURLConnectionSendAsynchronousRequestQueueCompletionHandler(id self, SEL _cmd, NSURLRequest* request, NSOperationQueue* queue, SendAsynchronousCompletionHandlerBlock completionHandler)
    {
    NSLog(@"Implementation Intercept in %s", __PRETTY_FUNCTION__);
    OriginalNSURLConnectionSendAsynchronousRequestQueueCompletionHandler(self, _cmd, request, queue, completionHandler);
    }
static NSData* MyNSURLConnectionSendSynchronousRequestReturningResponseError(id self, SEL _cmd, NSURLRequest* request, NSURLResponse** response, NSError** error)
    {
    NSLog(@"Implementation Intercept in %s", __PRETTY_FUNCTION__);
    NSData* data = OriginalNSURLConnectionSendSynchronousRequestReturningResponseError(self, _cmd, request, response, error);
    return data;
    }
 @implementation NSURLConnection (MyNSURLConnection)
+ (void) load
    {
    // Create onceToken
    static dispatch_once_t onceToken;
    // Use dispatch_once to make sure this runs only once in the lifecycle
    dispatch_once(&onceToken,
        ^{
        NSLog(@"Injecting code to NSURLConnection");
        [self injectImplementationToNSURLConnectionSendAsynchronousRequestQueueCompletionHandler];
        [self injectImplementationToNSURLConnectionSendSynchronousRequestReturningResponseError];
        // Some other methods I intercept, just as reference, they work as tested to init an NSURLConnection object
        // I will skip their implementation which is similar to what I show here
        [self injectImplementationToNSURLConnectionConnectionWithRequestDelegate];
        [self injectImplementationToNSURLConnectionInitWithRequestDelegateStartImmediately];
        [self injectImplementationToNSURLConnectionInitWithRequestDelegate];
        [self injectImplementationToNSURLConnectionStart];
        });
    }
+ (void) injectImplementationToNSURLConnectionSendAsynchronousRequestQueueCompletionHandler
    {
    // Replace the method on the same class that's used
    // in the calling code
    Class class =  [NSURLConnection class];
    // The Original +sendAsynchronousRequest:queue:completionHandler:
    SEL originalSelector = @selector(sendAsynchronousRequest:queue:completionHandler:);
    // The Replacement method implementation
    IMP replacement = (IMP)MyNSURLConnectionSendAsynchronousRequestQueueCompletionHandler;
    // This will eventually hold the original sendAsynchronousRequest:queue:completionHandler:
    IMP* store = (IMP*)&OriginalNSURLConnectionSendAsynchronousRequestQueueCompletionHandler;
    IMP originalImp = NULL;
    Method method = class_getClassMethod(class, originalSelector);
    if (method)
        {
        const char* type = method_getTypeEncoding(method);
        // Replace the original method with the MyNSURLConnectionSendAsynchronousRequestQueueCompletionHandler
        originalImp = class_replaceMethod(class, originalSelector, replacement, type);
        if (!originalImp)
            {
            originalImp = method_getImplementation(method);
            }
        }
    // Put the original method IMP into the pointer
    if (originalImp && store)
        {
        *store = originalImp;
        }
    }
+ (void) injectImplementationToNSURLConnectionSendSynchronousRequestReturningResponseError
    {
    // Replace the method on the same class that's used
    // in the calling code
    Class class =  [NSURLConnection class];
    // The Original +sendSynchronousRequest:returningResponse:error: selector
    SEL originalSelector = @selector(sendSynchronousRequest:returningResponse:error:);
    // The Replacement method implementation
    IMP replacement = (IMP)MyNSURLConnectionSendSynchronousRequestReturningResponseError;
    // This will eventually hold the original sendSynchronousRequest:returningResponse:error:
    IMP* store = (IMP*)&OriginalNSURLConnectionSendSynchronousRequestReturningResponseError;
    IMP originalImp = NULL;
    Method method = class_getClassMethod(class, originalSelector);
    if (method)
        {
        const char* type = method_getTypeEncoding(method);
        // Replace the original method with the MyNSURLConnectionSendSynchronousRequestReturningResponseError
        originalImp = class_replaceMethod(class, originalSelector, replacement, type);
        if (!originalImp)
            {
            originalImp = method_getImplementation(method);
            }
        }
    // Put the original method IMP into the pointer
    if (originalImp && store)
        {
        *store = originalImp;
        }
    }

这些方法的不同之处在于我不能让我的代码混进原始实现中，并且没有任何错误发生。

下面是我测试它的代码:

- (IBAction) executeURLRequest: (UIButton*)sender
    {
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"https://My.URL/file.json"]];
    [request setValue:@"API_KEY" forHTTPHeaderField:@"X-My-Auth-Token"];
    NSURLResponse* response;
    NSError* error;
    // Doesn't work, my swizzle method is not invoked
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
    // Doesn't work, my swizzle method is not invoked
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue currentQueue] completionHandler:
        ^(NSURLResponse *response, NSData *data, NSError *error)
        {
        if (error) NSLog(@"NSURLConnection failed: %@", [error debugDescription]);
        NSLog(@"Made the NSURLRequest to My");
        }];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0),
        ^{
        // It works, I get to see my message of the method invoked to the output console
        NSURLConnection* connection = [[NSURLConnection alloc] initWithRequest:request delegate:nil startImmediately:YES];
        });
    }

我不知道，我觉得挺好的…你觉得呢?

首先，不要在调试和/或学习目的之外混用系统框架方法。它是脆弱的，会在操作系统的发布中崩溃，并且当发现与系统框架混淆的应用程序时，将不会被批准或删除。

其次，NSURLConnection很可能被实现为一个类集群。因此，很可能有一些子类实现了实际的连接，而您正在混淆抽象父类的实现，它什么也不做。

虽然你需要特别小心搅拌，但我不知道苹果有什么政策禁止搅拌系统框架。我自己已经搅拌了这些相同的类，并且SDK已经包含在应用商店的应用程序中。

NSURLConnection不是作为类集群实现的，尽管NSURLSession是。

我编写了在Apigee iOS SDK中混合NSURLConnection和NSURLSession的代码。查看这里的NSURLConnection的实现:

https://github.com/apigee/apigee-ios-sdk/blob/master/source/Classes/Services/NSURLConnection%2BApigee.m

这是我的代码，我能够swizzle (void)sendAsynchronousRequest:(NSURLRequest *)请求队列:(NSOperationQueue )队列completionHandler:(void (^)(NSURLResponse， NSData*， NSError*))处理程序

// + (void)sendAsynchronousRequest:(NSURLRequest *)request queue:(NSOperationQueue *)queue completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*))handler
void (*gOrigNSURLConnection_sendAsynchronousRequestQueueCompletionHandler)(id,SEL,NSURLRequest *,NSOperationQueue *,DataTaskCompletionBlock) = NULL;

static void NSURLConnection_logTelemetrySendAsynchronousRequestQueueCompletionHandler(id self, SEL _cmd, NSURLRequest* request, NSOperationQueue* queue, DataTaskCompletionBlock completionHandler)
{
    NSLog(@"i am catched");
    return gOrigNSURLConnection_sendAsynchronousRequestQueueCompletionHandler( self, _cmd ,request,queue,completionHandler);
}
// in swizzling method 
// NSURLConnection  + (void)sendAsynchronousRequest:queue:completionHandler:
    selMethod = @selector(sendAsynchronousRequest:queue:completionHandler:);
    impOverrideMethod = (IMP) NSURLConnection_logTelemetrySendAsynchronousRequestQueueCompletionHandler;
    origMethod = class_getClassMethod(c,selMethod);
    gOrigNSURLConnection_sendAsynchronousRequestQueueCompletionHandler = (void *)method_getImplementation(origMethod);
    if( gOrigNSURLConnection_sendAsynchronousRequestQueueCompletionHandler != NULL )
    {
        method_setImplementation(origMethod, impOverrideMethod);
        ++numSwizzledMethods;
    } else {
        NSLog(@"error: unable to swizzle + (void)sendAsynchronousRequest:queue:completionHandler:");
    }

测试代码

- (IBAction)clickSendAsyncWithBlock:(id)sender {
    NSURL *URL = [NSURL URLWithString:@"http://localhost:8000/a.txt"];
    NSURLRequest *request = [NSURLRequest requestWithURL:URL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60];
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[NSOperationQueue mainQueue]
                           completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
                               NSString *myString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
                               NSLog(@"got %@" , myString);
                           }];
}

结果:

2014-06-17 10:31:29.086遥测[3017:60b]我被抓住了

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