objective-c - 需要澄清协议中声明的属性规则

Question

我对协议中声明的属性有一些疑问。

返回类型差异

@protocol IHaveProperties

@required

@property (nonatomic, strong) IAmOfTypeX *propertyOfProtocolType;
@property (nonatomic, strong) NSArray *array;

@end

@interface ClassThatHasProperties : NSObject<IHaveProperties>

@property (nonatomic, strong) ImplementationOfTypeX *propertyOfProtocolType;
@property (nonatomic, strong) NSMutableArray *array;

@end

好的，所以我用协议/类组合尝试了这个，令我懊恼的是，它编译了。

这是如何运作的？这在技术上不符合接口吗？

属性声明修饰符

@protocol IHaveProperty

@required

@property (nonatomic, strong, readonly) *example;

@end

@interface HaveProperty : NSObject<IHaveProperty>

@property (nonatomic, strong, readonly) *example;

@end

我的 Mac 现在正在重新启动，所以我无法尝试，但我认为这没关系，因为协议声明没有任何支持。调用者不会对所有修饰符感兴趣，只会对实现协议的类感兴趣。

Answer 1

如果你看一下<NSObject> Protocol，你会发现它把方法和属性放在一起：

@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

您必须具有 useddescription或superclass属性。与函数相比，如何处理属性没有区别。实现协议的类将提供协议属性的 getter 和/或 setter。同样，拥有委托对象的类将调用其属性，例如：self.delegate.propertyName.