在fmt.Sprintf格式字符串中多次引用相同的参数 [英] Refer to the same parameter multiple times in a fmt.Sprintf format string

问题描述

我有这个功能:

func getTableCreationCommands(v string) string {
    return `
        CREATE TABLE share_` + v + ` PARTITION OF share FOR VALUES IN (` + v + `);
        CREATE TABLE nearby_` + v + ` PARTITION OF nearby FOR VALUES IN (` + v + `);
    `
}

有点奇怪...有没有办法使用 fmt.Sprintf 格式化字符串?

It's a little wonky... is there a way to format the string using fmt.Sprintf?

类似这样的东西:

func getTableCreationCommands(v string) string {
    return fmt.Sprintf(`
        CREATE TABLE share_%v PARTITION OF share FOR VALUES IN (%v);
        CREATE TABLE nearby_%v PARTITION OF nearby FOR VALUES IN (%v);
    `, v, v, v, v)
}

但是不需要通过 v 4次吗?

but without the need to pass v 4 times?

推荐答案

软件包fmt

import "fmt" 

显式参数索引:

在Printf，Sprintf和Fprintf中，默认行为是每个格式化动词来格式化调用中传递的连续参数.但是，动词前的符号[n]表示而是将第n个单索引参数格式化.

In Printf, Sprintf, and Fprintf, the default behavior is for each formatting verb to format successive arguments passed in the call. However, the notation [n] immediately before the verb indicates that the nth one-indexed argument is to be formatted instead.

---

您可以一次传递变量 v .例如，

package main

import "fmt"

func getTableCreationCommands(v string) string {
    return fmt.Sprintf(`
        CREATE TABLE share_%[1]v PARTITION OF share FOR VALUES IN (%[1]v);
        CREATE TABLE nearby_%[1]v PARTITION OF nearby FOR VALUES IN (%[1]v);
    `, v)
}

func main() {
    fmt.Println(getTableCreationCommands(("X")))
}

游乐场: https://play.golang.org/p/DlafU_R_phq

输出:

CREATE TABLE share_X PARTITION OF share FOR VALUES IN (X);
CREATE TABLE nearby_X PARTITION OF nearby FOR VALUES IN (X);

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