iOS Review note 11: Protocols and proxies

a function
You can declare a method in a protocol (you cannot declare a variable).
As long as a class adheres to this protocol, it is equivalent to having all the method declarations in the agreement.
The parent class is a quasi-gatekeeper protocol, and subclasses also have methods in the protocol.
The agreement may also be subject to another agreement.
Base protocol NSObject (also the base class), the NSObject base class is also quasi-obey the base protocol.
The base protocol contains common memory management methods, such as the Release,retain method.


Two definitions
1 Protocol Definitions
@protocal Agreement name <NSObject>
Declaring methods
@end


2 Compliance Agreement
Class 2.1
@interface Class Name: Parent class name < protocol name 1, protocol name 2...>
@end


2.2 Protocol
@protocal protocol Name < protocol name 1, protocol name 2...>
@end


3 Key Words
@required to please implement, do not implement a warning
@optional Optional Implementation


4 Define a variable that must be subject to a protocol
NSObject < agreement name > obj1;
ID < agreement name > obj2;
@property (nonatomic, strong) ID < protocol name > P;


Three code examples

Myprotocal.h@protocal myprotocal <nsobject>-(void) protocoldefaultfun (), @required//default, requires implementation, does not implement report warning-(void ) Protocolrequiredfun (); @optional//optional implementation-(void) protocoloptionalfun (); @end

Mulprotocal.h@protocal mulprotocal <nsobject>-(void) mulprotocoldefaultfun (); @end

Person.h#import <Foundation/Foundation.h> @protocal myprotocal; @protocal mulprotocal;//or @protocal Myprotocal, mulprotocal;//as long as one class complies with an agreement, it has all the methods declared in the agreement @interface Person:object <myprotocal, mulprotocal> @end

Person.m#import "Person.h" #import "MyProtocal.h" #import "MulProtocal.h" @implementation person <myprotocal, mulprotocal>-(void) Protocoldefaultfun () {}-(void) Protocolrequiredfun () {}-(void) Protocoloptionalfun () {}-(void ) Mulprotocoldefaultfun () {} @end

Main.m#import <Foundation/Foundation.h> #import "MyProtocal.h" #import "Person.h" int main () {// Declares an object that complies with myprotocal nsobject<myprotocal>* obj1 = [[Person alloc] Init];obj1 = nil;id<myprotocal> Obj2 = [[ Person Alloc] Init];obj2 = nil;//return 0;}

Four agents

Ticketdelegate.h@protocol ticketdelegate <nsobject>-(int) leftticketsnumber; @end

Agent.h@protocol ticketdelegate, @interface agent:nsobject <ticketDelegate> @end//Agent.m#import "Agent.h" # Import "TicketDelegate.h" @implementation agent-(int) Leftticketsnumber{return 1;} @end

Person.h@class agent, @class ticketdelegate, @interface person:nsobject-(void) buyticket;//Proxy Properties @property (nonatomic , retain) ID <ticketDelegate> delegate; @end

Person.m#import "Person.h" #import "Agent.h" @implementation person-(void) buyticket{if (_delegate & [_delegate Leftticketsnumber] > 0) {NSLog (@ "buy ticket");}} @end

Main.m#import "Person.h" #import "Agent" int main () {@autopool {person* p = [[Person alloc]init]; agent* a = [[Agent alloc] init];p. Delegate = A; [P buyticket];} return 0;}

iOS Review note 11: Protocols and proxies