什么是Swift Playground中的lldb_expr？ [英] What is lldb_expr in Swift Playground?

问题描述

我试图向某人演示基本继承以及如何在覆盖init时默认调用超级初始化器：

I was trying to demonstrate basic inheritance to someone and how the super initializer is always called by default when overriding an init:

class Animal{
    init(){
        println("Animal has been initialized!")
    }
}

class Dog:Animal{
    var feet:Int = 4

    override init(){
        println("Dog has been initialized!")
    }
}

var d = Dog()

为什么我得到 {__ lldb_expr_380.Animal feet 4} ？当我在动物类下创建一个实例变量时，它就消失了。

Why is it that I get {__lldb_expr_380.Animal feet 4} on the last line? It goes away when I create an instance variable under the animal class.

推荐答案

我不是100％关于此，而是对我而言看起来很健全。

I am not 100% about this but to me this seems sane and logical.

你的 Animal 类是空的，所以编译器需要一种表达/打印类的方法/它的价值观。所以它的作用是打印 __ lldb_expr_380.Animal ，因为编译器不知道还有什么可以做。如果添加属性，例如 legs ，结果将变为： {{legs 2} feet 4} 。

Your Animal class is empty so the compiler needs a way to express / print the class / it's values. So what it does is print __lldb_expr_380.Animal because the compiler doesn't know what else to make of it. If you add a property, for example legs, the result becomes this: {{legs 2} feet 4}.

所以，根据我的理解，只要你有这个空的超类，编译器就会混淆，发生的错误就是打印出来 __ llb_expr_：some_number：.ClassName 而不是 {} 。

So, in my understanding whenever you have this empty superclass the compiler will get 'confused' and the error that happens is that it will just print out __llb_expr_:some_number:.ClassName instead of something like {}.

参考： http://discuss.codewithchris.com / t / episode-7-classes-error --- lldb-expr- / 150

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