7. protocol-OC

(1) What is a protocol?

(2) how to define a protocol

(3) how to use the Protocol

(1) What is a protocol?

1. An interface object negotiated between multiple objects.

2. provides a series of methods for communication between Protocol Implementers and proxies.

3. Similar to pure virtual functions in c ++ or interfaces in java.

(2) how to define a protocol

1. Only header files

2. method definition

@ProtocolMyprotocol

-(Void) init;

-(Int) updata :( int) time;

@ End

3. Not every method in the Protocol must be implemented.

@ Required [Method must be implemented]

@ Optional [Methods can be implemented and default]

The Protocol must inherit from the basic protocol NSObject

Protocols can be inherited

@ProtocolMyprotocol

@ Optional

-(Void) init;

@ Required

-(Int)>

A simple Protocol example

Protocol example:

How do I know whether the shwoinfo method is written.

5. determine whether an object has a response method.

Dynamically determines whether a method is implemented.

If ([testRespondsToSelector: @ Selector (showInfo :)])

{

[Test> YES;

}

(3) how to use the Protocol

Create a protocol:

#import 
 
  @protocol Myprotocol 
  
   @optional- (void) printValue:(int)value;@required- (int) printValue:(int)value1 andValue:(int)Value2;@end
  
 

Methods for implementing the Protocol:

/// TestProtocol. h // TestPortocal // Created by ccy on 13-12-21. // Copyright (c) 2013 ccy. all rights reserved. // # import
 
  
# Import "Myprotocol. h" @ interface TestProtocol: NSObject
  
   
{}-(Void) testValue :( int) Value; @ end
  
 

/// TestProtocol. m // TestPortocal // Created by ccy on 13-12-21. // Copyright (c) 2013 ccy. all rights reserved. // # import "TestProtocol. h "@ implementation TestProtocol-(void) testValue :( int) Value {NSLog (@" testValue value: % d \ n ", Value);}-(int) printValue :( int) value1 andValue :( int) Value2 {NSLog (@ "printValue value1: % d, value2: % d \ n", value1, Value2); return 0;}-(void) printValue :( int) value {NSLog (@ "printValue % d \ n", value);} @ end

Call, use protocol:

//// Main. m // TestPortocal // Created by ccy on 13-12-21. // Copyright (c) 2013 ccy. all rights reserved. // # import
 
  
# Import "TestProtocol. h "// # import" Myprotocol. h "int main (int argc, const char * argv []) {@ autoreleasepool {// insert code here... NSLog (@ "Hello, World! "); TestProtocol * testPtcl = [[TestProtocol alloc] init]; [testPtcl testValue: 2]; [testPtcl printValue: 30 andValue: 40]; // determine whether the method has implemented SEL sel = @ selector (printValue :); if ([testPtcl respondsToSelector: sel]) {[testPtcl printValue: 20];} [testPtcl release]; // implement the id using the Protocol
  
   
Myprotocol = [[TestProtocol alloc] init]; [myprotocol printValue: 103]; [myprotocol release];} return 0 ;}