10. Blocks application-OC

[BlocksIt refersFunction pointer]

Blocks was first transplanted from the local snow leopard of Apple to the iPhone. Blocks is widely used in multithreading.

(1) What is Blocks?

(2) differences between Blocks and c voice function pointers

(3) how to call Blocks

(4) How does proxy 2 communicate through Blocks

(1) What is Blocks?

Similar to the c speech function pointer, running requires support for compilers and Runtime (ios4.0 starts to support Blocks)

Blocks is used for communication between two objects, which is equivalent to a callback function.

(2) differences between Blocks and c voice function pointers

(3) how to call Blocks

Typedef definition:

_ Block Keyword:

Change to a global variable

Simple use of blocs:

Block statement:

Void (^ myblocks) (void) = NULL;

Block assignment:

Myblocks = ^ (void ){

NSLog (@ "in blocks ");

};

Block call:

Myblocks ();

Example 1:

Int (^ myblocks2) (int a, int B) = ^ (int a, int B) {// value int c = a + B; return c ;} int ret = myblocks2 (10, 20); // Execute

Example 2:

_ Block int sum = 0; // The global variable int (^ myblocks3) (int a, int B) = ^ (int a, int B) {sum = a + B; return sum;} myblock3 (20, 30 );

Example 3:

Typedef int (^ SumBlockT) (int, int); // defines a type of SumBlockT myblocks4 = ^ (int a, int B) {NSLog (@ "sum: % d ", a + B); return 0;} myblock4 (10, 12 );

(4) How does proxy 2 communicate through Blocks

Blocks Used for iphone development:

Define a blocks. The dog calls this blocks at a time;

A blocks is defined in a dog to store the blocks function defined in a person.

Dog:

. H

Void (^ BarkCallback) (Dog * thisDog, int count); // variable

-(Void)SetBark:( Void (^) (Dog * thisDog, int count) eachBark; // This function is exposed externally and assigned to people.

. M

-(Void) updatatime :( id) arg

{

If (BarkCallblack)

{

BarkCallback (self, barkCount );

}

}

-(Void) setBark :( void (^) (Dog * thisDog, int count) eachBark

{

[BarkCallblack release];

BarkCallblack = [eachBark copy]; // copy is because the setDog function may be released.

}

-(Void) dealloc

{

[BarkCallblack release];

[Super dealloc];

}

Persons:

In the setDog function:

[_ Dog setBark: ^ (Dog * thisDog, int count ){

NSLog (@ "person dog % d count % d \ n", thisDog. ID, count );

}]