11 协议

认识协议

//Drawable.h 文件#import <Foundation/Foundation.h>@protocol Drawable@property  NSInteger x;@property  NSInteger y;-(void)draw;+(void)createShape;//-(id)init;//-(void)dealloc;@optional-(void)moveToX:(NSInteger)x withY:(NSInteger)y;@end

使用协议

只出现警告信息而不是错误，是因为有运行时添加方法的机制。所以编译器会认为这样也未必就是错误。

#import <Foundation/Foundation.h>#import "Drawable.h"@interface BLNPoint : NSObject<Drawable> // 用<>准守协议@property  NSInteger x; @property  NSInteger y; // 协议的属性也可以不在头文件声明，直接自己创建实例变量和getter/setter方法。但是很少如此使用。@end

// 作为类型约束使用void process1(id<Drawable> obj){    [obj draw];    NSLog(@"[%ld,%ld]",(long)obj.x,(long)obj.y);}void process2(id obj){    if ([obj conformsToProtocol:@protocol(AProtocol) ]) {        [obj methodA];    }}void process3(id<BProtocol> obj){    [obj methodA];    [obj methodB];}

// - (BOOL)conformsToProtocol:(Protocol *)aProtocol;if ([obj conformsToProtocol:@protocol(AProtocol) ]) {    [obj methodA];}

更多协议模式

// -------------     定义协议    -------------@protocol AProtocol-(void)methodA;@end@protocol BProtocol <AProtocol>-(void)methodB;@end@protocol CProtocol-(void)methodC;@end@protocol Protocol// 默认会有一个@require。加了@optional之后，在再次遇到@require之前都会是可选性的。@require-(void)methodD;@optional -(void)moveToX:(NSInteger)x withY:(NSInteger)y;@end// -------------     遵守协议的类    -------------@interface ClassA : NSObject<AProtocol>@end@interface ClassB : NSObject<BProtocol>@end@interface ClassC : NSObject<AProtocol,CProtocol>@end

常用协议

@protocol NSObject- (BOOL)isEqual:(id)object;@property (readonly) NSUInteger hash;@property (readonly) Class superclass;- (Class)class OBJC_SWIFT_UNAVAILABLE("use 'anObject.dynamicType' instead");- (instancetype)self;- (id)performSelector:(SEL)aSelector;- (id)performSelector:(SEL)aSelector withObject:(id)object;- (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;- (BOOL)isProxy;- (BOOL)isKindOfClass:(Class)aClass;- (BOOL)isMemberOfClass:(Class)aClass;- (BOOL)conformsToProtocol:(Protocol *)aProtocol;- (BOOL)respondsToSelector:(SEL)aSelector;- (instancetype)retain OBJC_ARC_UNAVAILABLE;- (oneway void)release OBJC_ARC_UNAVAILABLE;- (instancetype)autorelease OBJC_ARC_UNAVAILABLE;- (NSUInteger)retainCount OBJC_ARC_UNAVAILABLE;- (struct _NSZone *)zone OBJC_ARC_UNAVAILABLE;@property (readonly, copy) NSString *description;@optional@property (readonly, copy) NSString *debugDescription;@end

@protocol NSCopying- (id)copyWithZone:(nullable NSZone *)zone;@end

@protocol NSMutableCopying- (id)mutableCopyWithZone:(nullable NSZone *)zone;@end

@protocol NSCoding- (void)encodeWithCoder:(NSCoder *)aCoder;- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder; // NS_DESIGNATED_INITIALIZER@end

@protocol NSFastEnumeration- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id __unsafe_unretained [])buffer count:(NSUInteger)len;@end