OC Protocol Protocol

I. Overview

• A protocol is a delegate (delegate)/proxy, which is an object that provides an opportunity to respond to changes in another object or to affect the behavior of another object.
• A protocol can only be used for one purpose, that is, to declare a heap of methods for an inherited class.
• The base class adheres to the Protocol, and its derived class also adheres to the protocol that its base class adheres to, meaning that the parent class's protocol can inherit from the quilt class.
• In OC, the class cannot inherit multiple, only single inheritance, but the protocol can inherit more.
• The method of the Protocol Declaration can be implemented by any class that inherits.
• Agreement <NSObject> is the base agreement for all agreements.
• A protocol can comply with an agreement, which means that one protocol can comply with (inherit) other agreements, so that it can have declarations of all methods of other protocols.
• There are also two keywords in the protocol @optional and @required, @optional modified method declaration tells the developer that this method can be implemented, or not be implemented. @required decorated method declaration tells the development that this method must be implemented, of course, the two keyword modification methods can be ignored, but Xcode will give a warning.

II. Protocol Definition Format

1 // protocol name defined by protocol name 2 @protocol MyProtocol <NSObject>3@required45@optional67  @end

Iii. examples

1 //entrusted by DemoViewController.h2 #import<UIKit/UIKit.h>3 4 @protocolDemodelegate <NSObject>5- (void) Seteditwithvalue: (NSString *) Avalue;6 @end7 8 @interfaceDemoviewcontroller:uiviewcontroller9 {Ten     ID<DemoDelegate>idelegate; One } A  - //This delegate is the Setdelegate method -@property (nonatomic, assign)ID<DemoDelegate>idelegate; the  - @end -  - //DEMOVIEWCONTROLLER.M + #import "DemoViewController.h" -  + @interfaceDemoviewcontroller () A { atNSString *ivarstring; - } -  -@property (nonatomic, copy) NSString *ivarstring; -  -- (void) print; in  - @end to  + @implementationDemoviewcontroller - @synthesizeidelegate; the @synthesizeivarstring; *  $- (void) PrintPanax Notoginseng { -[Self.idelegate Seteditwithvalue:@"Test"]; the } +  A @end the  +  - //To be trusted, be aware that the Code manager object is to be set in the delegate $ //DemoController.h $ #import<Foundation/Foundation.h> -  - #import "DemoViewController.h" the  - @interfaceDemocontroller:nsobject <DemoDelegate>Wuyi  the @end -  Wu //DEMOCONTROLLER.M - #import "DemoController.h" About  $ @interfaceDemocontroller () - { -Demoviewcontroller *Idvcontroller; - } A  +@property (nonatomic, retain) Demoviewcontroller *Idvcontroller; the  --(Instancetype) Initwithvalue: (NSString *) Avalue; $  the @end the  the @implementationDemocontroller the @synthesizeIdvcontroller; -  in-(Instancetype) Initwithvalue: (NSString *) Avalue the { the     if(self =[Super init]) About     { theSelf.idvcontroller =[[Demoviewcontroller alloc] init]; the [Self.idvcontroller setidelegate:self]; the     } +      -     returnSelf ; the }Bayi  the- (void) Seteditwithvalue: (NSString *) Avalue the { -     // to do -NSLog (@"Detail Page Edit value:%@", avalue); the } the  the @end

PS: The proxy object that is set in the delegate is the member property of the delegate, namely: the Getter and setter method @property delegate.

1 @interface Demoviewcontroller 2 {3   ID<DemoController> idelegate;   4 }56ID<DemoController> idelegate;

OC Protocol Protocol