老生常谈category增加属性的几种操作

正文

请到「今天看啥」查看全文

) { if (!cls) return NO; if (! type ) type = "" ; if (name && 0 == strcmp(name, "" )) name = nil; rwlock_writer_t lock(runtimeLock); assert(cls->isRealized()); // No class variables if (cls->isMetaClass()) { return NO; } // Can only add ivars to in -construction classes. if (!(cls->data()->flags & RW_CONSTRUCTING)) { return NO; } } // 重点在这最后一句，前面我们已经看到 objc_allocateClassPair 函数所分配的新类的flags位信息，在此处 & RW_CONSTRUCTING，必定为真，取反后跳过大括号向下执行。

3. 已经存在的类，经过测试，flag位为 RW_REALIZED|RW_REALIZING,设置函数如下:

static Class realizeClass(Class cls)
{
    runtimeLock.assertWriting();

    const class_ro_t *ro;
    class_rw_t *rw;
    Class supercls;
    Class metacls;
    bool isMeta;
    
    if (!cls) return nil;
    if (cls->isRealized()) return cls;
    assert(cls == remapClass(cls));

    // fixme verify class is not in an un-dlopened part of the shared cache?

    ro = (const class_ro_t *)cls->data();
    if (ro->flags & RO_FUTURE) {
        // This was a future class. rw data is already allocated.
        rw = cls->data();
        ro = cls->data()->ro;
        cls->changeInfo(RW_REALIZED|RW_REALIZING, RW_FUTURE);
    } else {
        // Normal class. Allocate writeable class data.
        rw = (class_rw_t *)calloc(sizeof(class_rw_t), 1);
        rw->ro = ro;
        rw->flags = RW_REALIZED|RW_REALIZING;
        cls->set

请到「今天看啥」查看全文