英文:
How to pass an interface argument to a variadic function in Golang?
问题
我有一个可变参数函数func Results(messages ...Message)，它接受一个接口Message。如果我传递一个类型为Message的单个消息，它可以正常工作，但如果我传递一个消息切片Result(slice...)，我会得到以下错误：
prog.go:38: cannot use messages (type []*SampleMessage) as type []Message in argument to Results
英文:
I have a variadic function Result func Results(messages ...Message) that accepts an interface Message. It works fine if I pass a single message of type Message, but if i pass a slice of message Result(slice...)
Here is the error I get:
prog.go:38: cannot use messages (type []*SampleMessage) as type []Message in argument to Results
答案1
得分: 3
你需要稍微重构一下。问题在于[]*SampleMessage无法转换为[]Message。处理这个问题的方法是将messages切片声明为[]Message类型。然后，你可以将SampleMessage的实例追加到其中，而不会出现任何问题，并使用...语法将它们传递到可变参数函数中。这是修改后可以编译的示例：http://play.golang.org/p/cQUIZTz_vo - 唯一的变化是在main函数的第一行，我将var messages []Message。如果你尝试以相反的顺序进行操作（例如使用[]*SampleMessages然后使用[]Message(messages)进行转换），它将失败。据我所知，这是解决你的问题的最实用的方法。
英文:
You need to restructure slightly. The issue is that a []*SampleMessage cannot convert to []Message. The way to handle this though, is to declare the messages slice as being of type []Message. Then you can append instances of SampleMessage to it without any problems and pass them into your variadic function with the ... syntax. Here's your example modified to compile; http://play.golang.org/p/cQUIZTz_vo - only change is on the first line of main where I have var messages []Message. If you try to do this in the reverse order (like use a []*SampleMessages then do a conversion with []Message(messages) as you pass it) it will fail. So as far as I know, this is the most practical way to solve your problem.
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