IOS Block Usage

1. Define Block

/ * return void , parameter is void block*/

void (^blockreturningvoidwithvoidargument) ( void );

/ * callback integer, two parameters are integers and character block*/

int (^blockreturningintwithintandchararguments) ( int , char );

/ * return void , array with block , each block has a parameter of type integer */

void (^arrayoftenblocksreturningvoidwinintargument[ ]) ( int );

/* Define object method use Block,block to pass in a nsstring parameter, return void*/

-(void) Testblockwithparam: (void (^) (nsstring *text)) block;

2. Use block

-(void) Testblockwithparam: (void (^) (nsstring *text)) block{

NSLog(@ "start test");

// define parameter x, use in Testx

int x = 1;

int (^TESTX) (int) = ^ (int num2) {

return x+num2;

};

NSLog (@ "Use x:%d", Testx ());

// use the __block identifier to define a parameter y that can modify the value in the block

__block int y = 2;

int (^testy) (int) = ^ (int num2) {

if (Num2 > ten) {

y = ten;

}Else{

y = 2;

}

return y+num2;

};

NSLog(@ "when num2 > 10,sum =%d", testy);

NSLog(@ "when num2 <= 10,sum =%d", testy (8));

[nsthreadsleepfortimeinterval:1.0f];

Block (@ "Success");

}