[Objective-C Runtime] 类与对象

struct objc_class {
   //isa指针指向Class
    Class _Nonnull isa  OBJC_ISA_AVAILABILITY;#if !__OBJC2__
    Class _Nullable super_class  OBJC2_UNAVAILABLE; // 父类
    const char * _Nonnull name OBJC2_UNAVAILABLE; // 类名
    long version  OBJC2_UNAVAILABLE; // 类的版本信息，默认为0
    long info  OBJC2_UNAVAILABLE; // 类信息，供运行时使用的一些位标识
    long instance_size  OBJC2_UNAVAILABLE; // 类的实例变量大小
   // 类的成员变量列表
    struct objc_ivar_list * _Nullable ivars  OBJC2_UNAVAILABLE; 
    // 方法定义列表
    struct objc_method_list * _Nullable * _Nullable methodLists  OBJC2_UNAVAILABLE; 
    // 方法缓存
    struct objc_cache * _Nonnull cache  OBJC2_UNAVAILABLE; 
    // 协议列表
    struct objc_protocol_list * _Nullable protocols OBJC2_UNAVAILABLE; #endif} OBJC2_UNAVAILABLE;

typedef struct objc_class *Class;

/// Represents an instance of a class.struct objc_object {
    Class _Nonnull isa  OBJC_ISA_AVAILABILITY;
};

- (void)verifyClassTypeRelation{    
    //Use `object_getClass` get Class's `isa`
    
    Dog *aDog = [[Dog alloc] init];
    Class dogCls = object_getClass(aDog); 
    NSLog(@"isa->%@ , super_class->%@", dogCls, class_getSuperclass(dogCls));   
    // print:isa->Dog, super_class->Animal

    Class dogMetaCls = objc_getMetaClass([NSStringFromClass(dogCls) UTF8String]);
    if (class_isMetaClass(dogMetaCls)) {    
       NSLog(@"YES, metaCls->%@ , metaCls's super_Class->%@, metaCls's isa->%@", dogMetaCls, class_getSuperclass(dogMetaCls), object_getClass(dogMetaCls)); 
              //print: YES, metaCls->Dog , metaCls's super_Class->Animal, metaCls's isa->NSObject
    }else{       
        NSLog(@"NO");    }
        
    Animal *animal = [[Animal alloc] init];
    Class animalCls = object_getClass(animal); 
    NSLog(@"isa->%@ , super_class->%@", animalCls, class_getSuperclass(animalCls)); 
       //print: isa->Animal , super_class->NSObject


    Class animalMetaCls = objc_getMetaClass([NSStringFromClass(animalCls) UTF8String]);
    
    if (class_isMetaClass(animalMetaCls)) {    
        NSLog(@"YES, metaCls->%@ , metaCls's super_Class->%@, metaCls's isa->%@", animalMetaCls, class_getSuperclass(animalMetaCls), object_getClass(animalMetaCls));  
         //print:YES, metaCls->Animal , metaCls's super_Class->NSObject, metaCls's isa->NSObject
    }else{   
        NSLog(@"NO");
    }
    
    Class viewMetaCls = objc_getMetaClass([NSStringFromClass([UIView class]) UTF8String]); 
        
        if (class_isMetaClass(viewMetaCls)) {    
               
            NSLog(@"YES, metaCls->%@ , metaCls's super_Class->%@, metaCls's isa->%@", viewMetaCls, class_getSuperclass(viewMetaCls), object_getClass(viewMetaCls));        
           //print:YES, metaCls->UIView , metaCls's super_Class->UIResponder, metaCls's isa->NSObject
    }
    
    Class rootMetaCls = objc_getMetaClass([NSStringFromClass([NSObject class]) UTF8String]);    
           
           if (class_isMetaClass(rootMetaCls)) {       
            NSLog(@"YES, metaCls->%@ , metaCls's super_Class->%@, metaCls's isa->%@", rootMetaCls, class_getSuperclass(rootMetaCls), object_getClass(rootMetaCls));      
             //print:YES, metaCls->NSObject , metaCls's super_Class->NSObject, metaCls's isa->NSObject
    }
    
}

isa->Dog, super_class->Animal
YES, metaCls->Dog , metaCls's super_Class->Animal, metaCls's isa->NSObject
isa->Animal , super_class->NSObject
YES, metaCls->Animal , metaCls's super_Class->NSObject, metaCls's isa->NSObject
YES, metaCls->UIView , metaCls's super_Class->UIResponder, metaCls's isa->NSObject
YES, metaCls->NSObject , metaCls's super_Class->NSObject, metaCls's isa->NSObject

isa->Dog, super_class->Animal
YES, metaCls->Dog , metaCls's super_Class->Animal, metaCls's isa->NSObject

/***********************************************************************
* _objc_allocateFutureClass
* Allocate an unresolved future class for the given class name.
* Returns any existing allocation if one was already made.
* Assumes the named class doesn't exist yet.
* Locking: acquires runtimeLock**********************************************************************/

Class _objc_allocateFutureClass(const char *name)
{    rwlock_writer_t lock(runtimeLock);

    Class cls;
    NXMapTable *map = futureNamedClasses();    
if ((cls = (Class)NXMapGet(map, name))) {        
// Already have a future class for this name.
        return cls;
    }

    cls = _calloc_class(sizeof(objc_class));
    addFutureNamedClass(name, cls);    return cls;
}

- (void)dynamicAddMethod{   
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wundeclared-selector"
    
    //1、Create and register class, add method to class
    Class cls = objc_allocateClassPair([Animal class], "Lion", 0);
    // 当为`Cat`时，返回的创建类cat地址为0x0,将`Cat`作为关键字
    //method: 返回`int32_t`,type使用`i`;参数：`id self`,type使用`@`;`SEL _cmd`,type使用`:`;
    //`NSDictionary *dic`,type使用`@`.综上，type使用'i@:@'
    ///具体类型可参照 https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html
    BOOL isAddSuccess = class_addMethod(cls, @selector(howlMethod), (IMP)testRuntimeMethodIMP, "i@:@"); 
    NSLog(@"%@", isAddSuccess ? @"添加方法成功" : @"添加方法失败");   
  
   //You can only register a class once.
    objc_registerClassPair(cls);   
     
    //2、Create instance of class
    id whiteCat = [[cls alloc] init];     
     
    NSLog(@"%@, %@", object_getClass(whiteCat), class_getSuperclass(object_getClass(whiteCat)));  
      // Print: Lion, Animal
    Class whiteCatCls = object_getClass(whiteCat);
    Class metaCls = objc_getMetaClass([NSStringFromClass(whiteCatCls) UTF8String]);
     
    if (class_isMetaClass(metaCls)) {      
      NSLog(@"YES, %@, %@, %@", metaCls, class_getSuperclass(metaCls), object_getClass(metaCls));   
         // Print: YES, Lion, Animal, NSObject
    }else{        
      NSLog(@"NO");
    }    
    //3、Method of class
    unsigned int methodCount = 0;
    Method *methods = class_copyMethodList(cls, &methodCount);  
     
     for (int32_t i = 0; i < methodCount; i ++) {
        Method aMethod = methods[i];     
        NSLog(@"%@, %s", NSStringFromSelector(method_getName(aMethod)), method_getTypeEncoding(aMethod));        
        //print:howlMethod, i@:@
    }
    free(methods);
    
    //4、call method
    int32_t result = (int)[whiteCat performSelector:@selector(howlMethod) withObject:@{@"name":@"lion", @"sex": @"male"}]; 
       NSLog(@"%d", result);//print:9
    
    //5、destory instance and class
    whiteCat = nil;    
    // Do not call this function if instances of the cls class or any subclass exist.
    objc_disposeClassPair(cls);    
     
     #pragma clang diagnostic pop

}

添加方法成功
 Lion, AnimalYES, Lion, Animal, NSObjecthowlMethod, i@:@
testRuntimeMethodIMP: {
    name = lion;
    sex = male;
}
9

@interface TestMetaClass: NSObject

@end


@implementation TestMetaClass

@end
int main(int argc, char * argv[]) {   
 @autoreleasepool {       
  BOOL result1 = [(id)[NSObject class] isMemberOfClass:[NSObject class]];  
  BOOL result2 = [(id)[NSObject class] isKindOfClass:[NSObject class]];        
  BOOL result3 = [(id)[TestMetaClass class] isMemberOfClass:[TestMetaClass class]];        
  BOOL result4 = [(id)[TestMetaClass class] isKindOfClass:[TestMetaClass class]];        
  NSLog(@"%d %d %d %d", result1, result2, result3, result4);        
  return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}
  //log2018-02-09 16:45:54.048040+0800 RuntimeUsage[9220:5754652] 0 1 0 0

- (BOOL)isMemberOf:aClass
{     return isa == (Class)aClass;
}

- (BOOL)isKindOf:aClass
{
     Class cls;    
    for (cls = isa; cls; cls = cls->superclass)        
    if (cls == (Class)aClass)              
        return YES;    
    return NO;
}