Objective-C Runtime基础
纠错
11 Aug 2015
本文主要梳理Objective-C的Runtime相关的结构
相关的类/结构体
NSObject
@interface NSObject <NSObject> {
Class isa OBJC_ISA_AVAILABILITY;
}
Class
typedef struct objc_class *Class;
也就是说Class 等价于 objc_class*
objc_class
struct objc_class {
Class isa OBJC_ISA_AVAILABILITY;
#if !__OBJC2__
Class super_class OBJC2_UNAVAILABLE;
const char *name OBJC2_UNAVAILABLE;
long version OBJC2_UNAVAILABLE;
long info OBJC2_UNAVAILABLE;
long instance_size OBJC2_UNAVAILABLE;
struct objc_ivar_list *ivars OBJC2_UNAVAILABLE;
struct objc_method_list **methodLists OBJC2_UNAVAILABLE;
struct objc_cache *cache OBJC2_UNAVAILABLE;
struct objc_protocol_list *protocols OBJC2_UNAVAILABLE;
#endif
} OBJC2_UNAVAILABLE;
objcivarlist
struct objc_ivar_list {
int ivar_count OBJC2_UNAVAILABLE;
#ifdef __LP64__
int space OBJC2_UNAVAILABLE;
#endif
/* variable length structure */
struct objc_ivar ivar_list[1] OBJC2_UNAVAILABLE;
} OBJC2_UNAVAILABLE;
objcmethodlist
struct objc_method_list {
struct objc_method_list *obsolete OBJC2_UNAVAILABLE;
int method_count OBJC2_UNAVAILABLE;
#ifdef __LP64__
int space OBJC2_UNAVAILABLE;
#endif
/* variable length structure */
struct objc_method method_list[1] OBJC2_UNAVAILABLE;
}
OBJC2_UNAVAILABLE;
objc_cache
struct objc_cache {
unsigned int mask /* total = mask + 1 */ OBJC2_UNAVAILABLE;
unsigned int occupied OBJC2_UNAVAILABLE;
Method buckets[1] OBJC2_UNAVAILABLE;
};
objcprotocollist
struct objc_protocol_list {
struct objc_protocol_list *next;
long count;
Protocol *list[1];
};
总结
好了，现在可以知道一个Objective-C的对象的基本结构是啥样子了，我再来画张属性图展示一下。
下面我来介绍一下Class这个类结构的各个变量的意义：
isa 指向MetaClass对象地址，（MetaClass其实是该类的类对象，Objective-C的类也属于对象，就是MetaClass对象）
superclass 指向父类的MetaClass对象
name 类名
version
info
instancesize
ivars
methodLists
cache
protocols
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