相当于Go中的Python string.format

发布于11月26日

在Python中，可以执行以下操作:

"File {file} had error {error}".format(file=myfile, error=err)

或者这样:

"File %(file)s had error %(error)s" % {"file": myfile, "error": err}

在围棋中，最简单的 Select 是:

fmt.Sprintf("File %s had error %s", myfile, err)

这不允许您交换格式字符串中的参数顺序，对于I18N，您需要这样做.Go does拥有template套餐，它需要类似以下内容:

package main

import (
    "bytes"
    "text/template"
    "os"
)

func main() {
    type Params struct {
        File string
        Error string
    }

    var msg bytes.Buffer

    params := &Params{
        File: "abc",
        Error: "def",
    }

    tmpl, _ := template.New("errmsg").Parse("File {{.File}} has error {{.Error}}")
    tmpl.Execute(&msg, params)
    msg.WriteTo(os.Stdout)
}

对于错误消息来说，这似乎是一条很长的路要走.有没有更合理的选项允许我给出独立于顺序的字符串参数？

With `strings.Replacer`

使用strings.Replacer，实现你的愿望的格式化程序是非常简单和紧凑的.

func main() {
    file, err := "/data/test.txt", "file not found"

    log("File {file} had error {error}", "{file}", file, "{error}", err)
}

func log(format string, args ...string) {
    r := strings.NewReplacer(args...)
    fmt.Println(r.Replace(format))
}

输出(在Go Playground上试用):

File /data/test.txt had error file not found

我们可以通过自动将括号添加到log()函数中的参数名称来使其使用起来更舒适:

func main() {
    file, err := "/data/test.txt", "file not found"

    log2("File {file} had error {error}", "file", file, "error", err)
}

func log2(format string, args ...string) {
    for i, v := range args {
        if i%2 == 0 {
            args[i] = "{" + v + "}"
        }
    }
    r := strings.NewReplacer(args...)
    fmt.Println(r.Replace(format))
}

输出(在Go Playground上试用):

File /data/test.txt had error file not found

是的，您可以说这只接受string个参数值.这是真的.稍有改进，这就不是真的了:

func main() {
    file, err := "/data/test.txt", 666

    log3("File {file} had error {error}", "file", file, "error", err)
}

func log3(format string, args ...interface{}) {
    args2 := make([]string, len(args))
    for i, v := range args {
        if i%2 == 0 {
            args2[i] = fmt.Sprintf("{%v}", v)
        } else {
            args2[i] = fmt.Sprint(v)
        }
    }
    r := strings.NewReplacer(args2...)
    fmt.Println(r.Replace(format))
}

输出(在Go Playground上试用):

File /data/test.txt had error 666

它的一个变体接受params作为map[string]interface{}，并将结果返回为string:

type P map[string]interface{}

func main() {
    file, err := "/data/test.txt", 666

    s := log33("File {file} had error {error}", P{"file": file, "error": err})
    fmt.Println(s)
}

func log33(format string, p P) string {
    args, i := make([]string, len(p)*2), 0
    for k, v := range p {
        args[i] = "{" + k + "}"
        args[i+1] = fmt.Sprint(v)
        i += 2
    }
    return strings.NewReplacer(args...).Replace(format)
}

试试Go Playground码.

With `text/template`

您的模板解决方案或提案也太过冗长.它可以像这样紧凑地编写(省略错误判断):

type P map[string]interface{}

func main() {
    file, err := "/data/test.txt", 666

    log4("File {{.file}} has error {{.error}}", P{"file": file, "error": err})
}

func log4(format string, p P) {
    t := template.Must(template.New("").Parse(format))
    t.Execute(os.Stdout, p)
}

输出(在Go Playground上try ):

File /data/test.txt has error 666

如果您想返回string(而不是将其打印到标准输出)，您可以这样做(在Go Playground上试用):

func log5(format string, p P) string {
    b := &bytes.Buffer{}
    template.Must(template.New("").Parse(format)).Execute(b, p)
    return b.String()
}