对象模型

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
@end

#import "ViewController.h"
#import <objc/runtime.h>
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
//动态创建对象
//创建一个名为DemoCustomView的类 它是UIView的子类
Class newClass = objc_allocateClassPair([UIView class], "DemoCustomView", 0);

//为该类增加一个名为report的方法
class_addMethod(newClass, @selector(report), (IMP)ReportFunction, "v@:");

//注册该类
objc_registerClassPair(newClass);

//创建一个DemoCustomView类的实例
id instanceOfNewClass = [[newClass alloc]init];

//调用report方法
[instanceOfNewClass performSelector:@selector(report)];
}
void ReportFunction(id self,SEL _cmd){
NSLog(@"This object is %p",self);
NSLog(@"Class is %@,and super is %@",[self class],[self superclass]);

Class currentClass = [self class];
for (int i = 1;i<5;i++){
NSLog(@"Following the isa pointer %d times gives %p",i,currentClass);
currentClass = object_getClass(currentClass);//获得对象的isa指针所指向的对象

}
NSLog(@"NSObject's class is %p",[NSObject class]);
NSLog(@"NSObject's meta class is %p",object_getClass([NSObject class]));

/*
2016-04-27 14:43:59.683 OC对象模型[11609:1157519] This object is 0x7fd208c2fe10
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] Class is DemoCustomView,and super is UIView
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] Following the isa pointer 1 times gives 0x7fd208c19080
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] Following the isa pointer 2 times gives 0x7fd208c32c70
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] Following the isa pointer 3 times gives 0x1008f6198
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] Following the isa pointer 4 times gives 0x1008f6198
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] NSObject's class is 0x1008f6170
2016-04-27 14:43:59.684 OC对象模型[11609:1157519] NSObject's meta class is 0x1008f6198
*/
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface ImagePickerReplaceMethodsHolder : NSObject
-(BOOL)shouldAutorotate;
-(UIInterfaceOrientation)preferredInterfaceOrientationForPresentation;
@end

#import "ImagePickerReplaceMethodsHolder.h"

@implementation ImagePickerReplaceMethodsHolder
-(BOOL)shouldAutorotate{
return  NO;
}

-(UIInterfaceOrientation)preferredInterfaceOrientationForPresentation{
return UIInterfaceOrientationPortrait;
}
@end

#import <UIKit/UIKit.h>

@interface ImagePickerViewDemo : UIImagePickerController

@end
#import "ImagePickerViewDemo.h"
#import "ImagePickerReplaceMethodsHolder.h"
#import <objc/runtime.h>
#define SYSTEM_VERSION_CREATE_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion]compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v) ([[[UIDevice currentDevice] systemVersion]compare:v options:NSNumericSearch] == NSOrderedAscending)
@implementation ImagePickerViewDemo
-(void)load{
static dispatch_once_t onceToken;
dispatch_once(&onceToken,^{

[self hackForImagePicker];
});

}

-(void)hackForImagePicker{
//iOS swizzling的应用
//动态替换类方法或实例方法
//API
//1.  class_replaceMethod 替换类方法的定义
//2.  method_exchangeImplementations 交换两个方法的实现
//3.  method_setImplementation 设置一个方法的实现
if (SYSTEM_VERSION_CREATE_THAN_OR_EQUAL_TO(@"6.0") && SYSTEM_VERSION_LESS_THAN(@"6.1")){

Method oldMethod1 = class_getInstanceMethod([UIImagePickerController class], @selector(shouldAutorotate));
Method newMethod1 = class_getInstanceMethod([ImagePickerReplaceMethodsHolder class], @selector(shouldAutorotate));
method_setImplementation(oldMethod1, method_getImplementation(newMethod1));

Method oldMethod2 = class_getInstanceMethod([UIImagePickerController class], @selector(preferredInterfaceOrientationForPresentation));
Method newMethod2 = class_getInstanceMethod([ImagePickerReplaceMethodsHolder class], @selector(preferredInterfaceOrientationForPresentation));
method_setImplementation(oldMethod2, method_getImplementation(newMethod2));

}

}
@end

#import <Foundation/Foundation.h>

@interface Father : NSObject

@end
#import "Father.h"

@implementation Father
{
int _father;
}
@end

#import "Father.h"

@interface Son : Father

@end
#import "Son.h"

@implementation Son
{
int _son;
}
@end

#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "Son.h"
int main(int argc, char * argv[]) {
Son *son = [[Son alloc]init];
/* 控制台打印
(lldb) p *son
(Son) $2 = {
Father = {
NSObject = {
isa = Son
}
_father = 0
}
_son = 0
}
*/
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}