我们可以使用Swift在操场上扩展一个类吗?

The following code runs perfectly if it is in a standalone command line app:

如果是在一个独立的命令行应用程序中，下面的代码可以完美地运行:

extension Int {
    func sayHello() {
    println("Hello, I'm \(self)")
    }
}

1.sayHello() 
2.sayHello()

However, in playground, it won't run, and the error is "(2 times)". Can we not extend a class in playground or how do we do it?

然而，在操场上，它不会跑，错误是“(2次)”。我们能不能在操场上开设一个班，或者我们怎么做?

1 个解决方案

#1

A few corrections:

一些修改:

• "(2 times)" is not an error. It means your code was executed two times.
• “(2次)”不是错误。这意味着您的代码被执行了两次。
• Int is a struct (value type), not a class
• Int是一个结构体(值类型)，而不是一个类

You can click the eye icon to see the output:

您可以点击眼睛图标查看输出: