The Block app in iOS

In this big winter, silently knocking on the keyboard, do not spray. Learning Swift today, learning about closures, discovering closures and OC blocks has a lot of similarities, re-learning and learning some of the advanced points of usage, as follows:

1.block Format Description: (return type) (^ block name) (parameter type) = ^ (parameter list) {Code Implementation};//if there are no arguments, the () of the argument list after the equals sign can omit the example:

void (^demoblock) () = ^ {

NSLog (@ "demo Block");

};

Int (^sumblock) (int, int) = ^ (int x, int y) {

return x + y;

};

The variables used in 2.block are retained as duplicates, and the copied variables of the block are preserved in the block, and by default, variables outside the block are read-only in the block! When you use the __block keyword, you can also modify the value of the external variable in the block. 3. A typedef can be used to define the type of block, which is convenient for subsequent direct use, such as:

typedef double (^myblock) (double, double);

Myblock area = ^ (double x, double y) {

return x * y;

};

Myblock sum = ^ (double A, double b) {

return a + B;

};

NSLog (@ "%.2f", Area (10.0, 20.0));

NSLog (@ "%.2f", SUM (10.0, 20.0));

4. Although typedef can simplify the definition of block, the TypeDef keyword is not frequently used in real-world development because the block is highly flexible, especially when passed as a parameter. The purpose of using block is to immediately declare the following using the official array traversal method:

-(void) Enumerateobjectsusingblock: (void (^) (id obj, Nsuinteger idx, BOOL *stop))block;

If you use TypeDef, you need: (1) typedef void (^Enumerateblock) (ID obj, Nsuinteger idx, BOOL *stop);(2)-(void) Enumerateobjectsusingblock: (enumerateblock) block;

The end result is that Enumerateblock has no other use other than defining the type.

5.Block can be passed directly as a parameter

Nsarray *array = @[@ "Zhang San", @ "John Doe", @ "Harry", @ "Zhao Liu"];

[Array enumerateobjectsusingblock:^ (ID obj, Nsuinteger idx, BOOL *stop) {

NSLog (@ "%d content is%@", (int) idx, obj);

if ([@ "Harry" Isequaltostring:obj]) {

*stop = YES;

}

}];

Or:

Myblock Sumblock = ^ (double x, double y) {
return x * y;

};

-(void) add: (int) number withnumber: (int) withnumber Sumblock: (myblock) block
{

NSLog (@ "Execute add: (int) number withnumber: (int) withnumber Sumblock: (void (^) (void)) block");
NSLog (@ "hahaha--4 and 2 multiplied equals:%f", Block (Number,withnumber));

}

[Self add:4 withnumber:2 sumblock:sumblock];

6. Since block is a data type, block can be added to the array as a special object

#pragma mark defined and added to an array

@property (nonatomic, strong) Nsmutablearray *myblocks;

Int (^sum) (int, int) = ^ (int x, int y) {

return [self sum:x y:y];

};

[Self.myblocks Addobject:sum];

Int (^area) (int, int) = ^ (int x, int y) {

return [self area:x y:y];

};

[Self.myblocks Addobject:area];

#pragma mark calls the block stored in the array

Int (^func) (int, int) = Self.myblocks[index];

return func (x, y);

7. Remove circular references

Local variables are strongly referenced by default and are freed after they leave their scope using the __weak keyword, you can declare a local variable as a weak reference

__weak demoobj *weakself = self;

N References weakself in block, the block no longer makes a strong reference to self

Int (^sum) (int, int) = ^ (int x, int y) {

return [weakself sum:x y:y];

};

8. Today's focus, referring to the framework of AFN, blocks call success or failure function arguments according to the function, and pass in the parameters as follows:

Because the main still used to judge success and failure functions, so look at the uncomfortable classmate can self-repair, will success replaced by add, will failure replaced multiplied

-(void) Viewdidload {
[Super Viewdidload];
Self.isbool = true;//is added when Isbool equals true, or multiplied

[Self setcompletionblockwithsuccess:^ (int x,int y) {
NSLog (@ "Add equals:%d", x+y);

NSLog (@ "Success");


} failure:^ (int x,int y) {

NSLog (@ "Multiplies equals:%d", x*y);
NSLog (@ "failure");


}];

}

-(void) Setcompletionblock: (void (^) (void)) block {

Block ();
NSLog (@ "Setcompletionblock number2:%d number3:%d", Self.number2,self.number3);
}


-(void) Setcompletionblockwithsuccess: (void (^) (int x,int y)) success
Failure: (void (^) (int x,int y)) failure
{

Self.completionblock = ^{

Self.number2 = 10;
Self.number3 = 20;


if (Self.isbool = = true) {//Determine which parameter is passed in, execute success or failure
NSLog (@ "start adding");
Success (SELF.NUMBER2,SELF.NUMBER3);//parameter passed in setcompletionblockwithsuccess
}else{
NSLog (@ "Start multiplying");
Failure (SELF.NUMBER2,SELF.NUMBER3);//parameter passed in setcompletionblockwithsuccess
}
};


}

The Block app in iOS