protocol协议时为了补充Objective-C 只能单继承的缺陷而增加的一个新功能。Objective-C重所有的方法都是虚方法,所以在oc重也就没有关键字 virtual一说,有了协议可以补充
Objective-C单继承的缺陷,协议并不是一个真正的类,在协议的里面只声明方法不实现,并且在协议当中不能声明实例变量,如果一个类实现了某一个协议的方法,那么称折各类遵
循(遵守,采用)了这个协议,正式的协议在类中必须被实现,一个类可以实现多个协议,一个协议也可以被多个类实现,
格式 format:
@protocol protocol_name<protocol,....>
required_Method_Declarations //默认是required 在类中必须被实现
@optional
optional_Method_Declarations // 在类中可以选择性的实现,
@required
required_Method_Declarations //在类中必须被实现,
@end
// MyPoint.h #import <Foundation/Foundation.h> //xieyi 协议 protocol @protocol showOn @required -(void)printOn; @end // lei @interface MyPoint : NSObject<showOn,NSCopying>{ int x; int y; } @property (nonatomic,assign)int x,y; -(id)initWithX:(int)_x andY:(int)_y; @end // leibie fenlei category 分类 @interface MyPoint(MoveSet) -(void)moveToX:(int)_x andY:(int)_y; @end
// MyPoint.m #import "MyPoint.h" @implementation MyPoint @synthesize x,y; -(id)initWithX:(int)_x andY:(int)_y{ if(_x==0) x=1; if(_y==0) y=1; x=_x; y=_y; return self; } //copyWithZone 方法,避免浅拷贝 -(id)copyWithZone:(NSZone *)zone{ MyPoint* newPoint=[[MyPoint allocWithZone:zone] initWithX:x andY:y]; return newPoint; } -(void)printOn{ NSLog(@" x = %d , y = %d ",x,y); } @end @implementation MyPoint(MoveSet) -(void)moveToX:(int)_x andY:(int)_y{ x=_x; y=_y; } @end
// Circle.h #import <Foundation/Foundation.h> #import "MyPoint.h" @interface Circle : NSObject<showOn>{ MyPoint* point; int radius; } @property (nonatomic,copy)MyPoint* point; @property (nonatomic,assign)int radius; -(id)initWithPoint:(MyPoint* )_p andRadius:(int)_r; -(id)initWithPoint:(MyPoint *)_p ; @end
// Circle.m #import "Circle.h" @implementation Circle @synthesize point; @synthesize radius; //重写初始化方法 -(id)initWithPoint:(MyPoint *)_p andRadius:(int)_r{ if(_r==0) { radius=1; } if(_p==nil) return nil; if(self=[super init]) { if(point!=_p) { if(point) [point release]; point =[[MyPoint alloc]initWithX:_p.x andY:_p.y]; } } radius=_r; return self; } //重写初始化方法, -(id)initWithPoint:(MyPoint*)_p{ self=[self initWithPoint:_p andRadius:10]; return self; } //实现协议中的方法。 -(void)printOn{ NSLog(@"point(x,y) = (%d,%d),radius = %d",point.x,point.y,radius); } @end