英文:
How can I unpack a slice as a partial function argument?
问题
我正在使用exec.Command，它接收一个可变数量的字符串作为其第二个参数。例如：
out, err = exec.Command("python3", "script_name.py", "argument", "--flag", "--another")
我也可以使用切片并使用...进行解包：
var args = []string{"script_name.py", "argument", "--flag", "--another"}
out, err = exec.Command("python3", args...)
但是，将两者混合使用是不起作用的：
var args = []string{"argument", "--flag", "--another"}
out, err = exec.Command("python3", "script_name.py", args...)
会出现错误：
./tester.go:12:29: exec.Command调用中的参数太多
已有 (string, string, []string...)
期望 (string, ...string)
这让我感到惊讶，因为在Python中类似的操作是可行的。
我尝试寻找这个特定情况的解决方法，但我找到的大多数资源只是关于一般切片的。我已经找到了一个"解决方法"（更像是一个变通方法），即在切片的开头添加"常量"部分，但我想确保我没有漏掉什么：
var args = os.Args
args = append([]string{"script_name.py"}, args...)
out, err := exec.Command("python3", args...).Output()
- 我是否漏掉了什么？有没有办法同时传递常量字符串和解包后的数组？
- 这里有什么语言限制？为什么要区分
string, string, string和string, string...？我很想更深入地了解这个问题。
英文:
I'm using exec.Command that receives a variable number of strings for its second parameter. For example:
out, err = exec.Command("python3", "script_name.py", "argument", "--flag", "--another")
I can also use a slice and unpack it using ...:
var args = []string{"script_name.py", "argument", "--flag", "--another"}
out, err = exec.Command("python3", args...)
BUT mixing the two does not work:
var args = []string{"argument", "--flag", "--another"}
out, err = exec.Command("python3", "script_name.py", args...)
fails with:
./tester.go:12:29: too many arguments in call to exec.Command
have (string, string, []string...)
want (string, ...string)
This is surprising to me since something similar would work in python.
I've tried looking for this specific case but most of the resources I found are just about slicing in general. I've "solved" it (more like a workaround) by prepending the "constant" part to the start of the slice, but wanted to make sure I'm not missing anything:
var args = os.Args
args = append([]string{"script_name.py"}, args...)
out, err := exec.Command("python3", args...).Output()
- Am I missing anything? Is there a way to pass both the constant string and the unpacked array?
- What are the language constraints here? Why is it distinguishing between
string, string, stringandstring, string...? I'd love to understand this more deeply.
答案1
得分: 3
- 不可以。
- 约束条件在规范中有详细说明（链接）：
> 如果最后一个参数可以赋值给切片类型 []T，并且后面跟着 ...，那么它将作为 ...T 参数的值传递，不会发生变化。
这是唯一一种情况，你可以将切片展开为可变参数，正如你所发现的。
英文:
-
No.
-
The constraints are detailed in the spec:
> If the final argument is assignable to a slice type []T and is followed by ..., it is passed unchanged as the value for a ...T parameter.
That is the only case in which you can explode a slice into a variadic parameter, as you have found.
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