The iOS Block interface reversely transmits values, and the iosblock interface reversely transmits values.

The iOS Block interface reversely transmits values, and the iosblock interface reversely transmits values.

 

In the previous blog "Introduction to iOS Block", I focused on analyzing the concept of iOS Block. This article will focus on their applications in development.

Block is an extension of the C language introduced by iOS4.0 + and Mac OS X 10.6 + to implement the features of anonymous functions.
In Wikipedia, Block is a feature that Apple Inc. adds to C, C ++, and Objective-C, allowing these languages to create closures using the syntax of lambda-like expressions. The closure statement is concise and clear: the closure is a function that can read internal variables of other functions.

In iOS development, Block has many functions, and reverse interface value transfer is one of them.

Suppose we have A requirement as follows: there is A button and A label on interface. Jump from interface A to interface B, enter A string in the input box of interface B, and display it on the label of interface. This is a typical example of reverse value transfer. The core of this example is: "enter A string in the input box of interface B and display it on the label of interface ". Block implements reverse value transfer.

 

1. Define Block attributes in the. h file of the second view controller:

// Define block @ property (nonatomic, copy) void (^ NextViewControllerBlock) (NSString * tfText );

 

@ Interface NextViewController () @ property (weak, nonatomic) IBOutlet UITextField * inputTF; @ end-(IBAction) BtnAction :( id) sender {// determine whether the block is empty if (self. nextViewControllerBlock) {self. nextViewControllerBlock (self. inputTF. text);} [self. navigationController popViewControllerAnimated: YES];}

 

 

2. Obtain the second view controller from the first view and use the second view controller to call the defined attributes:

@interface AViewController ()@property (weak, nonatomic) IBOutlet UILabel *nextVCInfoLabel;@end

 

- (IBAction)btnClicked:(id)sender {        NextViewController *nextVC = [[NextViewController alloc]init];    nextVC.NextViewControllerBlock = ^(NSString *tfText){        self.nextVCInfoLabel.text = tfText;    };        [self.navigationController pushViewController:nextVC animated:YES];}

 

 

Effect

 

 

Because XIB is used in this article, some UI details are omitted, and the code link of this article is attached: source code.

I hope you can comment on the problem. Thank you ~