使用runtime获取类的方法和变量

使用runtime获取类的方法和变量

获取属性和变量

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void ycObjc_copyIvar_copyProperies(Class pClass){
    
    unsigned int count = 0;
    Ivar *ivars = class_copyIvarList(pClass, &count);
    for (unsigned int i=0; i < count; i++) {
        Ivar const ivar = ivars[i];
        //获取实例变量名
        const char*cName = ivar_getName(ivar);
        NSString *ivarName = [NSString stringWithUTF8String:cName];
        NSLog(@"class_copyIvarList:%@",ivarName);
    }
    free(ivars);

    unsigned int pCount = 0;
    objc_property_t *properties = class_copyPropertyList(pClass, &pCount);
    for (unsigned int i=0; i < pCount; i++) {
        objc_property_t const property = properties[i];
        //获取属性名
        NSString *propertyName = [NSString stringWithUTF8String:property_getName(property)];
        //获取属性值
        NSLog(@"class_copyProperiesList:%@",propertyName);
    }
    free(properties);
}

获取方法列表

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void ycObjc_copyMethodList(Class pClass){
    unsigned int count = 0;
    Method *methods = class_copyMethodList(pClass, &count);
    for (unsigned int i=0; i < count; i++) {
        Method const method = methods[i];
        //获取方法名
        NSString *key = NSStringFromSelector(method_getName(method));
        
        NSLog(@"Method, name: %@", key);
    }
    free(methods);
}

其他runtime方法

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// 获取类名
const char *className = class_getName(pClass);

// 获取元类
Class metaClass = objc_getMetaClass(className);

// 获取对象方法
Method method = class_getInstanceMethod(pClass, @selector(someFunc));

// 获取类方法
Method method = class_getClassMethod(pClass, @selector(someFunc));

// 获取IMP
IMP imp = class_getMethodImplementation(pClass, @selector(someFunc));

一些思考

定义一个 Person 类如下，并取得该类的类和元类，判断以下代码是否能获取到方法

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@interface Person : NSObject
- (void)instanceFunc;
+ (void)classFunc;
@end

=======

Person *person = [Person alloc];
Class pClass = object_getClass(person);
Class metaClass = objc_getMetaClass(className);

class_getInstanceMethod

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Method method1 = class_getInstanceMethod(pClass, @selector(instanceFunc));
Method method2 = class_getInstanceMethod(metaClass, @selector(instanceFunc));

Method method3 = class_getInstanceMethod(pClass, @selector(classFunc));
Method method4 = class_getInstanceMethod(metaClass, @selector(classFunc));

// 结果 method1 method4 可以获取到， method2 method3 获取不到

class_getClassMethod

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Method method1 = class_getClassMethod(pClass, @selector(instanceFunc));
Method method2 = class_getClassMethod(metaClass, @selector(instanceFunc));

Method method3 = class_getClassMethod(pClass, @selector(classFunc));
Method method4 = class_getClassMethod(metaClass, @selector(classFunc));

// 结果全部可以获取到
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IMP imp1 = class_getMethodImplementation(pClass, @selector(instanceFunc));
IMP imp2 = class_getMethodImplementation(metaClass, @selector(instanceFunc));

IMP imp3 = class_getMethodImplementation(pClass, @selector(classFunc));
IMP imp4 = class_getMethodImplementation(metaClass, @selector(classFunc));

// 都可以获取到 IMP，但是 imp2 和 imp3 相同， 是找不到时默认返回的_objc_msgForward

为什么获取元类的类方法仍然可以获取到方法？

查看objc源码可知可以看到底层获取了 cls->getMeta() 的 instance 方法

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Method class_getClassMethod(Class cls, SEL sel)
{
    if (!cls  ||  !sel) return nil;

    return class_getInstanceMethod(cls->getMeta(), sel);
}

继续查看 getMeta 方法

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Class getMeta() {
    if (isMetaClassMaybeUnrealized()) return (Class)this;
    else return this->ISA();
}

如果判断是元类的时候，会返回this, 所以对元类获取类方法仍然可以获取到方法

为什么class_getMethodImplementation获取不存在的方法也会返回值？

直接看源码

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__attribute__((flatten))
IMP class_getMethodImplementation(Class cls, SEL sel)
{
    IMP imp;
    if (!cls  ||  !sel) return nil;
    lockdebug_assert_no_locks_locked_except({ &loadMethodLock });
    imp = lookUpImpOrNilTryCache(nil, sel, cls, LOOKUP_INITIALIZE | LOOKUP_RESOLVER);
    // Translate forwarding function to C-callable external version
    if (!imp) {
        return _objc_msgForward;
    }
    return imp;
}

当imp找不到时会返回 _objc_msgForward