Block, blockb

Block, blockb

// 1 declare block

// 2 implement block

// 3 call the block

// Declare the function pointer

// Void (* ptest1) (void)

// Declare the block to point to an anonymous Function

Void (^ block1) (void );

Int (^ block2) (int a, int B );

Int (^ block3) (int a, int B );

Typedef void (^ block4) (void );

Typedef int (^ block5) (int a, int B );

 

// Block implementation

// Block1 points to an anonymous function. An anonymous function must end with a semicolon. If the block parameter type is void, the parameters of the anonymous function to be pointed can be omitted without writing. Other parameters cannot be omitted.

// The returned value of a block pointing to an anonymous function can be omitted (all types of return values can be omitted)

Block1 = ^

{
Printf ("block1 \ n ");

};

// The anonymous function is used to calculate the sum of a + B

Block2 = ^ (int a, int B)

{

Return a + B;

};

Block3 = ^ (int a, int B)

{
Return a-B;

};

// The role of bl4 is block4

Block4 bl4;

Bl4 = ^

{
NSLog (@ "block4 ");

};

Block5 bl5;

Bl5 = ^ (int a, int B)

{
Return a/B;

 

};

// Block call

Block1 ();

Int sum = block2 (2, 5 );

Printf ("% I \ n", sum );

Int mut = block3 (5, 3 );

Printf ("% I \ n", mut );

Bl4 ();

NSLog (@ "% I", bl5 (8, 2 ));

######################################## #########

Void test1 (void)

{

Printf ("test1 \ n ");

}

Void test2 (void)

{

Printf ("test2 \ n ");

}

Int test3 (int a, int B)

{

Return a + B;

}

Int test4 (int a, int B)

{

Return a-B;

}

 

(1) // call the C function by function name

Test1 ();

(2) // declare the function pointer. The function pointer points to the test1 function.

// Function pointer can point to function

Void (* ptest1) (void );

Ptest1 = test1;

// Call a function through a pointer

Ptest1 ();

Void (* ptest2) (void );

Ptest2 = test2;

Ptest2 ();

// Call by function name

Int result = test3 (2, 5 );

Printf ("% d", result );

// Call with function pointer

Int (* ptest3) (int a, int B );

Ptest3 = test3;

Int result = ptest3 (2, 5 );

Printf ("% d", result );

Int (* ptest4) (int a, int B );

Ptest4 = test4;

Int sum = ptest4 (5, 2 );

Printf ("% d", sum );

// Typedef custom type

Typedef int MYINT;

MYINT I = 10;

Printf ("% d", I );

 

Typedef void (* tdftest1) (void );

Tdftest1 t1 = test1;

// T1 = test1;

T1 ();

Typedef int (* tdfTest3) (int a, int B );

TdfTest3 t3 = test3;

Int a = t3 (5, 2 );

Printf ("% d", );

// Practice

There is a warning when calling some controls in the block. You can use the following method to release the warning:

_ Block UILabel * label = self. label;

_ SecondController. bl = ^ (float size)

{
Label. font = [UIFont systemFontOfSize: size];

};

 

# Import <UIKit/UIKit. h>

 

// Declare block

Typedef void (^ block) (float size );

 

 

 

@ Interface SecondViewController: UIViewController

-(IBAction) pressSteper :( id) sender;

 

// Use strong to encapsulate attributes for a block

// If the block attribute is encapsulated, the declared block must be modified with typedef.

@ Property (strong, nonatomic) block bl;

 

 

 

 

@ End