NSObject可以说是OC类的万物之源了,今天我们就来好好看看他的定义.

/* NSObject.h
Copyright (c) 1994-2012, Apple Inc. All rights reserved.
*/

ifndef OBJC_NSOBJECT_H

define OBJC_NSOBJECT_H

if OBJC

include <objc/objc.h>

include <objc/NSObjCRuntime.h>

@class NSString, NSMethodSignature, NSInvocation;

//定义了一个名为NSObject的协议.
@protocol NSObject

• (BOOL)isEqual:(id)object;
  //这个方法很常见,我们经常用来比较一个对象是否相同或者值是否相等.相同返回yes.而它是通过什么比较的呢?就是下面的hash值.
  @property (readonly) NSUInteger hash;

@property (readonly) Class superclass;//父类.

• (Class)class OBJC_SWIFT_UNAVAILABLE("use 'anObject.dynamicType' instead");//不知道干啥用的.
• (instancetype)self; //返回自己的对象.

//执行一个包装方法.与普通相比,它可以执行到runtime阶段时候才有的方法.下面的不带参数,带一个参数,带两个参数.

• (id)performSelector:(SEL)aSelector;
• (id)performSelector:(SEL)aSelector withObject:(id)object;
• (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;

//是否从NSObject继承下来的.

• (BOOL)isProxy;
  //是不是某个类或者父类的实例
• (BOOL)isKindOfClass:(Class)aClass;
  //是不是某个类的实例.
• (BOOL)isMemberOfClass:(Class)aClass;
  //是不是遵守某个协议.
• (BOOL)conformsToProtocol:(Protocol *)aProtocol;
  //是不是接受者实现或者继承了某个方法可以响应这个消息.
• (BOOL)respondsToSelector:(SEL)aSelector;

//引用计数器加一

• (instancetype)retain OBJC_ARC_UNAVAILABLE;
  //引用计数器减一
• (oneway void)release OBJC_ARC_UNAVAILABLE;
  //当当前自动释放池释放时释放.
• (instancetype)autorelease OBJC_ARC_UNAVAILABLE;
  //返回接收对象的引用计数器.不是很准,因为自动释放池可能会推迟释放.
• (NSUInteger)retainCount OBJC_ARC_UNAVAILABLE;
  //返回一段结构体--对象被分配的区域,价值不大.
• (struct _NSZone *)zone OBJC_ARC_UNAVAILABLE;

//接受者的描述.%@ 打印的东西
@property (readonly, copy) NSString *description;
@optional
//同上,不过是在Debug模式下的.
@property (readonly, copy) NSString *debugDescription;

@end

OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0)
OBJC_ROOT_CLASS
OBJC_EXPORT
//正式开始定义NSObject了.
@interface NSObject <NSObject> {
//类指针.
Class isa OBJC_ISA_AVAILABILITY;
}
//触发,当类或者分类加入Runtimel的时候.

• (void)load;
  //是类接受到的第一个消息.
• (void)initialize;
  //初始化

• (instancetype)init

if NS_ENFORCE_NSOBJECT_DESIGNATED_INITIALIZER

NS_DESIGNATED_INITIALIZER

endif

;

//不知道

• (instancetype)new OBJC_SWIFT_UNAVAILABLE("use object initializers instead");
  //历史遗留方法初始分配内存.
• (instancetype)allocWithZone:(struct _NSZone *)zone OBJC_SWIFT_UNAVAILABLE("use object initializers instead");
  //..
• (instancetype)alloc OBJC_SWIFT_UNAVAILABLE("use object initializers instead");

• (void)dealloc OBJC_SWIFT_UNAVAILABLE("use 'deinit' to define a de-initializer");
  //有垃圾回收机制时候代替dealloc.
• (void)finalize OBJC_DEPRECATED("Objective-C garbage collection is no longer supported");
  //返回调用copyWithZone的结果
• (id)copy;
  //返回调用mutableCopyWithZone的结果
• (id)mutableCopy;
  //返回接受者.协议不同

• (id)copyWithZone:(struct _NSZone *)zone OBJC_ARC_UNAVAILABLE;
  //返回接受者.协议不同.
• (id)mutableCopyWithZone:(struct _NSZone *)zone OBJC_ARC_UNAVAILABLE;
  //实例化对象是否响应给定的方法
• (BOOL)instancesRespondToSelector:(SEL)aSelector;
  //是否遵守协议.
• (BOOL)conformsToProtocol:(Protocol *)protocol;
  //找出接受者实现方法地址.

• (IMP)methodForSelector:(SEL)aSelector;
  //同上,不过是类方法.

• (IMP)instanceMethodForSelector:(SEL)aSelector;
  //runtime不能找不到方法时访问

• (void)doesNotRecognizeSelector:(SEL)aSelector;
  //重定向
• (id)forwardingTargetForSelector:(SEL)aSelector OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0);
• (void)forwardInvocation:(NSInvocation *)anInvocation OBJC_SWIFT_UNAVAILABLE("");
  //返回一个对象包括方法描述的定义.
• (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector OBJC_SWIFT_UNAVAILABLE("");

• (NSMethodSignature *)instanceMethodSignatureForSelector:(SEL)aSelector OBJC_SWIFT_UNAVAILABLE("");
  //是否允许弱引用

• (BOOL)allowsWeakReference UNAVAILABLE_ATTRIBUTE;
  //是否增加弱引用
• (BOOL)retainWeakReference UNAVAILABLE_ATTRIBUTE;
  //是否是给定类的子类或者是相同的.

• (BOOL)isSubclassOfClass:(Class)aClass;
  //动态的提供一个方法的实现.
• (BOOL)resolveClassMethod:(SEL)sel OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0);
• (BOOL)resolveInstanceMethod:(SEL)sel OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0);
  //获得当前hash值
• (NSUInteger)hash;
  //获取父类
• (Class)superclass;
• (Class)class OBJC_SWIFT_UNAVAILABLE("use 'aClass.self' instead");
  //描述
• (NSString *)description;
  //Debug模式下的描述.
• (NSString *)debugDescription;

@end

endif

endif