使用class_getInstanceMethod - 在类层次结构中实现的方法在哪里?

时间:2013-04-09 18:20:20

标签: ios objective-c objective-c-runtime

是否有可能找到class_getInstanceMethod检索到的方法来自类层次结构的位置?例如,假设A类实现了myMethod。现在说我已经在A1类中继承了A类。如果我调用class_getInstanceMethod(ClassA1, myMethod),是否可以判断结果方法是否已在ClassA1中被覆盖或直接来自A1?

如果你有权访问ClassA和ClassA1,我想可以比较一下IMP的内存地址,但是我没有直接访问A.

2 个答案:

答案 0 :(得分:15)

您始终可以访问类的超类,因此您可以使用相同的class_getInstanceMethod将其传递给class_getMethodImplementationSEL,并比较IMP地址以查看是否该方法被子类覆盖。

如果你想进入定义这种方法的根类,这会有点毛茸茸。

无论如何,这里是:

static inline BOOL isInstanceMethodOverridden(Class cls, SEL selector, Class *rootImpClass) {
    IMP selfMethod = class_getMethodImplementation(cls, selector);
    BOOL overridden = NO;
    Class superclass = [cls superclass];
    while(superclass && [superclass superclass]) {
        IMP superMethod = class_getMethodImplementation(superclass, selector);
        if(superMethod && superMethod != selfMethod) {
            overridden = YES;
            if(!rootImpClass) {
                //No need to continue walking hierarchy
                break;
            }
        }

        if(!superMethod && [cls respondsToSelector:selector])) {
            //We're at the root class for this method
            if(rootImpClass) *rootImpClass = cls;
            break;
        }

        cls = superclass;
        superclass = [cls superclass];
    }

    return overridden;
}

答案 1 :(得分:3)

这是我对雅各布代码的修改版本。我遇到了他的问题因为class_getMethodImplementation正在返回一个_objc_msgForward,它导致方法被视为被覆盖。我也不需要* rootImpClass,但它很简单,可以重新添加。

inline BOOL isInstanceMethodOverridden(Class cls, SEL selector)
{
    IMP selfImplementation = class_getMethodImplementation(cls, selector);

    BOOL overridden = NO;
    Class superclass = cls;

    while ((superclass = [superclass superclass]))
    {
        Method superMethod = class_getInstanceMethod(superclass, selector);
        if (superMethod && method_getImplementation(superMethod) != selfImplementation)
        {
            overridden = YES;
            break;
        }
    }

    return overridden;
}