可变参数函数传递

问题描述

情况:

我正在尝试编写一个简单的 fmt.Fprintf 包装器，该包装器使用可变数量的参数.这是代码:

I'm trying to write a simple fmt.Fprintf wrapper which takes a variable number of arguments. This is the code:

func Die(format string, args ...interface{}) {
    str := fmt.Sprintf(format, args)
    fmt.Fprintf(os.Stderr, "%v\n", str)
    os.Exit(1)
}

问题:

当我用 Die("foo")调用它时，得到以下输出(而不是" foo "):

When I call it with Die("foo"), I get the following output (instead of "foo"):

• 为什么在" foo "之后有"％！(EXTRA [] interface {} = [])"?
• 在 fmt.Fprintf 周围创建包装的正确方法是什么?
• Why is there "%!(EXTRA []interface {}=[])" after the "foo"?
• What is the correct way to create wrappers around fmt.Fprintf?

推荐答案

可变参数函数将参数作为类型的切片接收.在这种情况下，您的函数将收到名为 args 的 [] interface {} .当您将该参数传递给 fmt.Sprintf 时，您会将其作为类型为 [] interface {} 的单个参数传递.您真正想要的是将 args 中的每个值作为单独的参数传递(与接收它们的方式相同).为此，您必须使用 ... 语法.

Variadic functions receive the arguments as a slice of the type. In this case your function receives a []interface{} named args. When you pass that argument to fmt.Sprintf, you are passing it as a single argument of type []interface{}. What you really want is to pass each value in args as a separate argument (the same way you received them). To do this you must use the ... syntax.

str := fmt.Sprintf(format, args...)

Go规范此处也对此进行了解释.

This is also explained in the Go specification here.

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