IOS Rutime学习

1.什么是Runtime

Runtime是Object-C中的一个库，主要用C和汇编写的，OC编写的代码最终都会转换为Runtime的C代码，用于消息的转发和传递

2.Runtime的基本用法

2.1 常用方法介绍
2.1.1 class_getClassMethod 获取某个类的方法

Method personMethod  =  class_getClassMethod([Class class], oriSEL);

2.1.2 class_getInstanceMethod 获取某个类的实例方法

Method changeMethod1 =  class_getInstanceMethod([self class], @selector(changeFunc1));
Method changeMethod2 =  class_getInstanceMethod([self class], @selector(changeFunc2));

-(void)changeFunc1{
    NSLog(@"========== fuction1 ");
}
-(void)changeFunc2{
    NSLog(@"========== fuction2 ");
}

2.1.3 method_exchangeImplementations 交换两个方法

method_exchangeImplementations(changeMethod2, changeMethod1);

2.1.4 class_addMethod 添加方法
我们先定义个Class 叫PersonClass
第一个参数是添加对象类
第二个参数是添加的方法
第三个参数是添加方法的IMP 用class_getMethodImplementation来获取
第四个参数是 传入方法是什么返回，是否带参 "v@:"等同于返回为void 不带参数

PersonClass *person = [[PersonClass alloc]init];
BOOL isAddSuccess =  class_addMethod([person class], @selector(addClass), class_getMethodImplementation([self class], @selector(addClass)), "v@:");
    if(isAddSuccess){
        [person performSelector:@selector(addClass)];
    }

2.1.4 class_replaceMethod替换方法
第一个参数是替换对象类
第二个参数是替换的方法
第三个参数是替换方法的IMP 用class_getMethodImplementation来获取
第四个参数是 传入方法是什么返回，是否带参 "v@:"等同于返回为void 不带参数

PersonClass *person = [[PersonClass alloc]init];
 BOOL replaceMethod = class_replaceMethod([person class], @selector(getName), class_getMethodImplementation([self class],@selector(changeClass)),"v@:");
    if(replaceMethod){
        [person performSelector:@selector(getName) withObject:nil];
    }

2.1.5 objc_setAssociatedObject objc_getAssociatedObject属性关联

OBJC_EXPORT void
objc_setAssociatedObject
(
id _Nonnull object,//被关联对象
const void * _Nonnull key,//关联的key
 id _Nullable value,//关联的值,属性名
objc_AssociationPolicy policy//策略一般使用OBJC_ASSOCIATION_RETAIN_NONATOMIC
)

static char *overviewKey;
NSArray *array = [NSArray arrayWithObjects:@"a",@"b",@"c",nil];
NSString *arrayDesc = @"this is arrayDesc";
    //关联
objc_setAssociatedObject(array, &overviewKey, arrayDesc, OBJC_ASSOCIATION_RETAIN);
 NSString *associatedDesc = (NSString *)objc_getAssociatedObject(array, &overviewKey); NSLog(@"associatedDesc:%@", associatedDesc);
 //取消关联
objc_setAssociatedObject(array, &overviewKey, nil, OBJC_ASSOCIATION_RETAIN);
NSString *associatedDesc2 = (NSString *)objc_getAssociatedObject(array, &overviewKey);
 NSLog(@"associatedDesc2:%@", associatedDesc2);

2.1.6获取类属性

 PersonClass *person = [[PersonClass alloc]init];
    unsigned int count;
    //获取类属性列表
    objc_property_t *propertyList = class_copyPropertyList([person class], &count);
    for(int i=0;i<count;i++){
        objc_property_t property = propertyList[i];
        NSLog(@"property name=%@",[NSString stringWithCString:property_getName(property) encoding:NSUTF8StringEncoding]);
    }
    
    free(propertyList);
    //获取类方法列表
    Method *methodList = class_copyMethodList([person class],  &count);
    for(int i=0;i<count;i++){
         Method method =  methodList[i];
        NSString *str =  NSStringFromSelector(method_getName(method));
        NSLog(@"method name=%@",str);
    }
    free(methodList);
    //获取成员变量
    Ivar *ivarList = class_copyIvarList([person class],  &count);
    for(int i=0;i<count;i++){
        Ivar ivar = ivarList[i];
        NSString *str = [NSString stringWithUTF8String:ivar_getName(ivar)];
        NSLog(@"ivar name=%@",str);
    }
    free(ivarList);

3 Runtime 消息转发

在runtime 中 我们用objc_msgSend来传递消息，但是在父类和子类都找不到对应的方法时，runtime会执行如下机制

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了解消息转发的原理，我们可以在forwardingTargetForSelector进行捕获 避免Unrecognized Selector的错误

+(BOOL)resolveClassMethod:(SEL)sel{
    if (sel == @selector(messageTest)) {
        NSLog(@"1======resolveClassMethod");
        return YES;
    }
    return NO;
}
+(BOOL)resolveInstanceMethod:(SEL)sel{
    if (sel == @selector(messageTest)) {
        NSLog(@"1======resolveInstanceMethod");
        return YES;
    }
    return NO;
}
- (id)forwardingTargetForSelector:(SEL)aSelector {
    if (aSelector == @selector(messageTest)) {
        NSLog(@"2======forwardingTargetForSelector");
     }
     return nil;
}