我们可以使用 Swift 在 Xcode 的操场上扩展一个类吗？

Question

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

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?

Answer 1

A few corrections:

• "(2 times)" is not an error. It means your code was executed two times.
• Int is a struct (value type), not a class

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