英文:
Variadic functions parameters pass-through
问题
Situation:
我正在尝试编写一个简单的fmt.Fprintf包装器，它可以接受可变数量的参数。以下是代码：
func Die(format string, args ...interface{}) {
str := fmt.Sprintf(format, args)
fmt.Fprintf(os.Stderr, "%v\n", str)
os.Exit(1)
}
Problem:
当我使用Die("foo")调用它时，我得到以下输出（而不是"foo"）：
foo%!(EXTRA []interface {}=[])
- 为什么在"foo"之后会有"%!(EXTRA []interface {}=[])"？
- 如何正确地创建
fmt.Fprintf的包装器？
英文:
Situation:
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)
}
Problem:
When I call it with Die("foo"), I get the following output (instead of "foo"):
> foo%!(EXTRA []interface {}=[])
- Why is there "%!(EXTRA []interface {}=[])" after the "foo"?
- What is the correct way to create wrappers around
fmt.Fprintf?
答案1
得分: 66
变长函数将参数作为类型为[]interface{}的切片接收。在这种情况下，您的函数接收一个名为args的[]interface{}类型的参数。当您将该参数传递给fmt.Sprintf时，您将其作为类型为[]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）。要做到这一点，您必须使用...语法。
str := fmt.Sprintf(format, args...)
这也在Go规范中解释了这里。
英文:
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...)
This is also explained in the Go specification here.
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