Block instead of delegate, use block as much as possible, and consider using protocol for a large number of delegate methods.

block instead of delegate, use block as much as possible, and consider using protocol for a large number of delegate methods.

1.Block syntax summary and examples are as follows:

1. Block mode of common code blocks

ReturnType (^blockname) (parametertypes) = ^returntype (parameters) {

Block code

};

Use no example:

Int (^ABC) (int a) = ^int (int a) {

return a+1;

};

int AA = ABC (2);

NSLog (@ "%d", AA);

2. Attribute Mode block

@property (nonatomic, copy) ReturnType (^blockname) (parametertypes);

Examples of Use:

1. Defining attributes

@property (nonatomic,copy) int (^testblock) (NSString *);

2. Setting Usage Properties

[Self Settestblock:^int (nsstring *a) {

return 0;

}];

3. Method Parameters Block

-(void) Somemethodthattakesablock: (ReturnType (^) (parametertypes)) Blockname {

Block code

};

Using Example 1:

1. Non-parametric definition and implementation:

-(void) Testblockfun: (void (^) ()) completion{

NSLog (@ "execute");

if (completion) {

Completion ();

}

}

2. Parameter-Free block invocation:

[Self testblockfun:^{

NSLog (@ "callback End");

}];

Using Example 2:

1. With parameter definition and implementation:

-(void) Testblockfun: (int (^) (int a,int b)) complate{

if (complate) {

int c = complate (3,5);

NSLog (@ "c:%d", c);

}

}

2. Block call with parameter type:

[Self testblockfun:^int (int a, int b) {

return a+b;

}];

4. As a parameter

[Someobject Somemethodthattakesablock: ^returntype (Parameters) {

Block code

}];

Examples of Use:

1. Definition and implementation

-(void) Testblockfun: (void (^) (NSString *)) complate{

if (complate) {

Complate (@ "Success");

}

}

2. Call

[Self testblockfun:^ (nsstring *str) {

NSLog (@ "str:%@", str);

}];

5. Using typedef definitions

typedef returntype (^typename) (parametertypes);

TypeName blockname = ^ (parameters) {

};

Examples of Use:

typedef void (^blocktestname) (NSString *);

Call:

[Self setname:^ (nsstring *a) {

}];

2.Block Modified value: Use __block to modify the value of an external variable inside the block.

__block int someincrementer = 0;

[Someobject somemethodthattakesablock:^{

someincrementer++;

}];

3.Block Loop reference, block will hold object, block object also has block, will cause block's circular reference, workaround:

__weak typeof (self) weakself = self;//@weakify (self);

[Self somemethodthattakesablock:^{

[Weakself Action];

}];

Block instead of delegate, use block as much as possible, and consider using protocol for a large number of delegate methods.