將塊傳遞給異步方法

我將一個塊傳遞給稍後執行此塊的異步方法。我的應用程序崩潰，如果我沒有複製該塊，然後傳遞給someMethod：成功：失敗：將塊傳遞給異步方法

有沒有方法來複制forwardInvocation中的塊：而不是在將它傳遞給someMethod之前將其複製：success：failure：？

流是的someMethod：成功：故障： - > forwardInvocation： - > HTTPGET：成功：失敗

HTTPGET：成功：失敗：執行的成功或根據HTTP狀態代碼故障塊。

// AppDelegate.h 

@interface AppDelegate : UIResponder <UIApplicationDelegate> 

@property (strong, nonatomic) id response; 
@property (strong, nonatomic) NSError *error; 

@end 

// AppDelegate.m 

@implementation AppDelegate 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    // The app crashes if the blocks are not copied here! 
    [[MyController new] someMethod:[^(NSString *response) { 
     self.response = response; 
     NSLog(@"response = %@", response); 
    } copy] failure:[^(NSError *error) { 
     self.error = error; 
    } copy]]; 

    return YES; 
} 

@end 

// MyController.h 

@protocol MyControllerProtocol <NSObject> 

@optional 


- (void)someMethod:(void (^)(NSString *response))success 
      failure:(void (^)(NSError *error))failure; 

@end 

@interface MyController : NSObject <MyControllerProtocol> 

@end 

// MyController.m 

#import "MyController.h" 
#import "HTTPClient.h" 

@implementation MyController 

- (void)forwardInvocation:(NSInvocation *)invocation { 
    [invocation retainArguments]; 

    NSUInteger numberOfArguments = [[invocation methodSignature] numberOfArguments]; 

    typedef void(^SuccessBlock)(id object); 
    typedef void(^FailureBlock)(NSError *error); 

    __unsafe_unretained SuccessBlock successBlock1; 
    __unsafe_unretained SuccessBlock failureBlock1; 
    [invocation getArgument:&successBlock1 atIndex:(numberOfArguments - 2)]; // success block is always the second to last argument (penultimate) 
    SuccessBlock successBlock = [successBlock1 copy]; 
    [invocation getArgument:&failureBlock1 atIndex:(numberOfArguments - 1)]; // failure block is always the last argument 
    FailureBlock failureBlock = [failureBlock1 copy]; 

    NSLog(@"successBlock copy = %@", successBlock); 
    NSLog(@"failureBlock copy = %@", failureBlock); 

    // Simulates a HTTP request and calls the success block later! 
    [HTTPClient httpGet:@"somerequest" success:successBlock failure:failureBlock]; 
} 

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel { 
    NSMethodSignature *methodSignature = [super methodSignatureForSelector:sel]; 
    return methodSignature; 
} 

@end 


// HTTPClient.h 

@interface HTTPClient : NSObject 

+ (void)httpGet:(NSString *)path 
     success:(void (^)(id object))success 
     failure:(void (^)(NSError *error))failure; 

@end 

// HTTPClient.m 

#import "HTTPClient.h" 

@implementation HTTPClient 

+ (void)httpGet:(NSString *)path 
     success:(void (^)(id object))success 
     failure:(void (^)(NSError *error))failure 
{ 
    // Invoke the method. 
    double delayInSeconds = 2.0; 
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC)); 
    dispatch_after(popTime, dispatch_get_main_queue(), 
       ^{ 
        success(@"foo"); 
       }); 
} 

@end

完整的源代碼可以在這裏找到：https://github.com/priteshshah1983/BlocksWithNSInvocation

能否請你幫忙嗎？

來源

2013-07-12 pshah

我們需要看到someMethod：失敗：我沒有看到你的代碼中的任何地方。 – kball

@kball someMethod：成功：失敗：未實現。因此，將調用methodSignatureForSelector：然後forwardInvocation：。 – pshah

@kball我修復了一些錯別字，很抱歉！它應該是一些方法：成功：失敗： – pshah

罪魁禍首是行[invocation retainArguments]。如果你註釋掉那條線，它就可以正常工作。（該行是從來沒有必要的，因爲無論如何調用從未存儲或使用異步）

說明：

想想-retainArguments一樣。它在對象指針類型的所有參數上調用retain。然後當調用被釋放時，它調用release。

但參數是堆棧（非複製）塊。 retain和release對它沒有影響（因爲它不是堆對象）。所以當它被保留時，什麼都不會發生，然後（從崩潰中）看起來調用是在某個時刻自動釋放的（這是一個完全正常的事情），所以調用的最終釋放和釋放是異步發生的。當調用被釋放時，它會嘗試釋放其保留的參數，但到那時它試圖向不再有效的堆棧塊發送消息，導致崩潰。

P.S.在forwardInvocation:塊的複製也是不必要的

來源

2013-07-13 02:06:56 newacct

將塊傳遞給異步方法

回答

相關問題