ios-对象原理探索六-类的结构和isa走位

MRPerson`类` vs 元类MRPerson的父类`NSObject`即`根元类` -- 不相等 MRPerson`类` vs 根元类的父类`NSObject`即`根类` -- 不相等 MRPerson`类` vs 根类的父类即 `nil` -- 不相等

假设我们有一个MRPerson类，并且- (void)sayHello和+ (void)sayHappy 都有实现

#import <Foundation/Foundation.h>
#import "MRPerson.h"
#import <objc/runtime.h>

#ifdef DEBUG
#define FYLog(format, ...) printf("%s\n", [[NSString stringWithFormat:format, ## __VA_ARGS__] UTF8String]);
#else
#define FYLog(format, ...);
#endif

void fyObjc_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);
}

void fyInstanceMethod_classToMetaclass(Class pClass){

    const char *className = class_getName(pClass);
    Class metaClass = objc_getMetaClass(className);

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

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

    NSLog(@"%s - %p-%p-%p-%p",__func__,method1,method2,method3,method4);
}

void fyClassMethod_classToMetaclass(Class pClass){

    const char *className = class_getName(pClass);
    Class metaClass = objc_getMetaClass(className);

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

    Method method3 = class_getClassMethod(pClass, @selector(sayHappy));
    // 元类 为什么有 sayHappy 类方法 0 1
    //
    Method method4 = class_getClassMethod(metaClass, @selector(sayHappy));

    NSLog(@"%s-%p-%p-%p-%p",__func__,method1,method2,method3,method4);
}

void fyIMP_classToMetaclass(Class pClass){

    const char *className = class_getName(pClass);
    Class metaClass = objc_getMetaClass(className);

    // - (void)sayHello;
    // + (void)sayHappy;
    IMP imp1 = class_getMethodImplementation(pClass, @selector(sayHello));
    IMP imp2 = class_getMethodImplementation(metaClass, @selector(sayHello));

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

    NSLog(@"%p-%p-%p-%p",imp1,imp2,imp3,imp4);
    NSLog(@"%s",__func__);
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        MRPerson *person = [MRPerson alloc];
        Class pClass     = object_getClass(person);
        fyObjc_copyMethodList(pClass);

        fyInstanceMethod_classToMetaclass(pClass);
        fyClassMethod_classToMetaclass(pClass);
        fyIMP_classToMetaclass(pClass);
    }
    return 0;
}

打印结果:

分析结果之前先看下这两个方法的源码结构:

class_getInstanceMethod(Class _Nullable cls, SEL _Nonnull name) 返回类的对象方法