Introduction and usage of block in objective-c language.

The block syntax was added in the iOS4.0 SDK , where more than a dozen APIs were used to block syntax.

The block object is also inherited and NSObject, and is a C-language-level syntax and runtime feature . Similar to the standard C function pointer . However, it is possible to maintain state data for similar objects in addition to executable statements .

Similar to the C language function pointers, but not exactly the same. Commonly used as a callback function.

Block vs. function operators:

The function pointer uses the ' * '

Block uses ' ^ '

Here is an example:

Apple.h file

#import <Foundation/Foundation.h>@interfacevoid (^SHUIGUO1) (void    Void (^SHUIGUO2) (void Void (^SHUIGUO3) (void);  -(void) Shuiguo; @end

APPLE.M file

#import "apple.h"@implementationApple- (void) shuiguo{if(_SHUIGUO1)//Determine if the _shuiguo1 is 0 {NSLog (@"I'm an apple ."); }    if(_SHUIGUO2) {NSLog (@"I'm a banana ."); }    if(_SHUIGUO3) {NSLog (@"I'm an orange ."); }}@end

Main function

#import<Foundation/Foundation.h>#import "apple.h"intMainintargcConst Char*argv[]) {@autoreleasepool {Apple*app =[[Apple Alloc]init]; Create an App object App.shuiguo1= ^{//print a shuiguo1 bolck. NSLog (@"I'm an apple .");        }; App.shuiguo2= ^{NSLog (@"I'm a banana .");        }; App.shuiguo3= ^{NSLog (@"I'm an orange .");        };　　[App Shuiguo]; method to invoke Shuiguo}return 0;}

Introduction and usage of block in objective-c language.