IOS開發－ 用block實現回調

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在IOS開發中經常會用到回調的情況，下面介紹如何用block實現回調。

1 #import <Foundation/Foundation.h>2 3 @interface BLock : NSObject4 5 + (void)getBlock:(void (^)(NSString *))someblock;6 7 @end

BLock.h

 1 #import "BLock.h" 2 #import <Foundation/Foundation.h> 3  4 @implementation BLock 5  6 + (void)getBlock:(void (^)(NSString *))someblock 7 { 8     NSLog(@"we are in a getBLock function"); 9     someblock(@"BLOCK GO GO");10 }11 @end

BLock.m

上面有一個BLock類， 裡面有個靜態方法，通過someblock回調一個string 資料。

 1 #import <Foundation/Foundation.h> 2 #import "BLock.h" 3 int main(int argc, const char * argv[]) 4 { 5  6     @autoreleasepool { 7          8         [BLock getBlock:^(NSString *str){NSLog(@"%@",str);}]; 9     }10     return 0;11 }

main.m

通過回調回來的str參數 ，在main裡面顯示。

輸出結果如下

2014-06-26 18:01:31.065 MyFirstApp[2430:303] we are in a getBLock function2014-06-26 18:01:31.066 MyFirstApp[2430:303] BLOCK GO GOProgram ended with exit code: 0

 

也可以將BLock.h和BLock.m的檔案改寫成如下：

1 #import <Foundation/Foundation.h>2 3 typedef  void (^ablock)(NSString *);//將block定義為新的類型4 5 @interface BLock : NSObject6 7 + (void)getBlock:(ablock)someblock;8 9 @end

BLock.h

 1 #import "BLock.h" 2 #import <Foundation/Foundation.h> 3  4  5 @implementation BLock 6  7 + (void)getBlock:(ablock)someblock 8 { 9     NSLog(@"we are in a getBLock function");10     someblock(@"BLOCK GO GO");11 }12 @end

BLock.m