问题描述
有一个问题，其中 MyObj.classnameis（TMyClass.classname）为true， TMyClass（MyObj） （MyObj as TMyclass）.doSomething 引发转换错误。
Got an issue where MyObj.classnameis(TMyClass.classname) is true and TMyClass(MyObj) works but (MyObj as TMyclass).doSomething throws a conversion error.
我真的不想帮助那些垃圾，虽然如果你想把它放在评论中是超级的。我只想知道 Obj之间的区别 和 Class（Obj） 是。
I don't really want any help with that junk, although if you want to put it in the comments that'd be super. I just would like to know what the difference between Obj as Class and Class(Obj) is.
推荐答案
铸件检查实际对象类型，有效，如果不是，则引发异常。 hard cast（ TMyClass（MyObj） style）不检查，它只是告诉编译器假设转换是有效的。
An as-cast checks the actual object type to make sure the cast is valid, and raises an exception if it's not. A "hard cast" (TMyClass(MyObj) style) does not check, it just tells the compiler to assume the cast is valid.
如果你有一个情况，ClassNameIs返回true但as-cast失败，这意味着你有两个不同的类在两个不同的单位具有相同的名称，并且as-cast试图转换错了一个。
If you've got a situation where ClassNameIs returns true but the as-cast fails, that means you have two different classes in two different units with the same name, and the as-cast is trying to cast to the wrong one. This also means that your hard-cast is casting to the wrong one, which could potentially lead to memory corruption.
运行完整的项目搜索TMyclass =可以看到其中你的多个声明是，并重命名其中一个类或使用一个完整的定义（obj作为MyUnit.TMyClass），所以编译器将知道你试图投射到哪个类。
Run a full project search for "TMyclass =" to see where your multiple declarations are, and either rename one of the classes or use a full definition (obj as MyUnit.TMyClass) so the compiler will know which class you're trying to cast to.
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