Objetive-C +load方法研究

/***********************************************************************
* _class_getLoadMethod
* fixme
* Called only from add_class_to_loadable_list.
* Locking: runtimeLock must be read- or write-locked by the caller.
**********************************************************************/
IMP 
_class_getLoadMethod(Class cls_gen)
{
    rwlock_assert_locked(&runtimeLock);

    class_t *cls = newcls(cls_gen);
    const method_list_t *mlist;
    uint32_t i;

    assert(isRealized(cls));
    assert(isRealized(cls->isa));
    assert(!isMetaClass(cls));
    assert(isMetaClass(cls->isa));

    mlist = cls->isa->data()->ro->baseMethods;
    if (mlist) for (i = 0; i < mlist->count; i++) {
        method_t *m = method_list_nth(mlist, i);
        if (0 == strcmp((const char *)m->name, "load")) {
            return m->imp;
        }
    }

    return NULL;
}

 

 

@interface initTest : NSObject

@end

 

@interface sub1 : initTest

@end

 

@interface sub2 : sub1

@end

 

@interface sub2 (category1)

@end

@interface sub2 (category2)

@end

 

 

//实现

 

@implementation initTest

//+(void)initialize
//{
//    NSLog(@"%s|%@  ",__func__ ,[self class]);
//}

+(void)load
{
    NSLog(@"%s  ",__func__ );
}

@end


@implementation sub1

//+(void)initialize
//{
//    NSLog(@"%s|%@  ",__func__ ,[self class]);
//}

//+(void)load
//{
//    NSLog(@"%s  ",__func__ );
//}
@end


@implementation sub2

//+(void)initialize
//{
//    NSLog(@"%s|%@  ",__func__ ,[self class]);
//}

+(void)load
{
    NSLog(@"%s  ",__func__ );
}

@end


@implementation sub2 (category1)

+(void)load
{
    NSLog(@"%s  ",__func__ );
}

@end

@implementation sub2 (category2)

+(void)load
{
    NSLog(@"%s  ",__func__ );
}

@end

2015-05-26 13:09:37.955 OCinitTest[79585:72506319] +[initTest load] 
2015-05-26 13:09:37.956 OCinitTest[79585:72506319] +[sub2 load] 
2015-05-26 13:09:37.956 OCinitTest[79585:72506319] +[sub2(category1) load]