LHF Objective-C语法（8）协议

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Printing.h

@protocol Printing1-(void)print1;@end@protocol Printing2-(void) print2;@end@protocol Printing3<Printing2>-(void)print3;@end

1、objc里的协议与java中的接口是同一个东西

2、协议可以遵从协议

2、说法：类Fraction遵从了Printing1、Printing3

//Fraction.h================================#import <Foundation/Foundation.h>#import "Printing.h"@interface Fracion : NSObject<Printing1,Printing3>{int numerator;int denominator;}-(Fraction*) initWithNumerator:(int) n denominator:(int)d;-(void) setNumerator:(int) n;-(void) setDenominator:(int) d;-(int) numerator;-(int) denominator;@end//Fraction.m================================#import "Fraction.h"@implementation Fraction-(Fraction*) initWithNumerator:(int) n denominator:(int)d{self = [super init];if(self){[self setNumerator:n];[self setDenominator:d];}}-(void) setNumerator:(int) n{numerator = n;}-(void) setDenominator:(int) d{denominator = d;}-(int) numerator{return numerator;}-(int) denominator{return denominator;}-(void)print1{NSLog(@"1:%d/%d",numerator,denominator);}-(void)print2{NSLog(@"2:%d/%d",numerator,denominator);}-(void)print3{NSLog(@"3:%d/%d",numerator,denominator);}

main.m

//main.m================Fraction *frac = [[Fraction alloc] initWithNumerator:3 denominator:5];<Printing1> p1 = frac;//id<Printing1> p1 = frac;[p1 print1];id<Printing1,Printing2,Printing3> p2 = frac;[p2 print2];[p2 print3];//用于判断对象是否遵从某个协议if([frac conformsToProtocol:@protocol(Printing1)]&&([frac conformsToProtocol:@protocol(Printing2)]&&([frac conformsToProtocol:@protocol(Printing3)]){NSLog(@"YES");}else{NSLog(@"NO");}[frac release];return 0;