11 協議

認識協議

//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

使用協議

只出現警告信息而不是錯誤，是因爲有運行時添加方法的機制。所以編譯器會認爲這樣也未必就是錯誤。

#import <Foundation/Foundation.h>
#import "Drawable.h"


@interface BLNPoint : NSObject<Drawable> // 用<>準守協議

@property  NSInteger x; 
@property  NSInteger y; 
// 協議的屬性也可以不在頭文件聲明，直接自己創建實例變量和getter/setter方法。但是很少如此使用。

@end

// 作爲類型約束使用
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];
}

更多協議模式

// -------------     定義協議    -------------
@protocol AProtocol

-(void)methodA;

@end

@protocol BProtocol <AProtocol>

-(void)methodB;

@end

@protocol CProtocol

-(void)methodC;

@end

@protocol Protocol
// 默認會有一個@require。加了@optional之後，在再次遇到@require之前都會是可選性的。
@require
-(void)methodD;
@optional 
-(void)moveToX:(NSInteger)x withY:(NSInteger)y;
@end
// -------------     遵守協議的類    -------------

@interface ClassA : NSObject<AProtocol>

@end

@interface ClassB : NSObject<BProtocol>

@end

@interface ClassC : NSObject<AProtocol,CProtocol>

@end

常用協議

@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