本文是上一文章《Golang实践录：命令行cobra库实例优化》 的优化，主要的子命令的业务实现的整理。

起因

上一版本实现的方式，还是有点不满意，格式也不对齐，重要的是，似乎不是正规的方式。

思路

cobra官方支持多级子命令，经研究测试发现，在实现三级子命令时，稍有麻烦。故舍弃官方的做法。同时参考了部分示例代码，结合得到本文的案例。

实现

旧版本如下：

var theCmd = []conf.UserCmdFunc{conf.UserCmdFunc {Name: "foo",ShortHelp: "just a foo help info",Func: foo,},conf.UserCmdFunc {"watch", "watch config file", testWatch,},
}func NewCmdTest() *cobra.Command{var cmd = &cobra.Command{Use:     name,Short:   shortDescription,Long:    longDescription,Example: example,RunE: func(cmd *cobra.Command, args []string) error {//klog.Println(common.DBName)if (len(args) == 0) {klog.Warning("no args found")common.PrintHelpInfo(theCmd)return nil}// !! 遍历并调用即可for _, item:=range theCmd {if (args[0] == item.Name) {item.Func(args)return nil}}klog.Printf("cmd '%v' not support", args[0])common.PrintHelpInfo(theCmd)return nil},}// note：使用子命令形式，下列可在help中展开// 命令参数，保存的值，参数名，默认参数，说明//cmd.Flags().StringVar(&mode, "db", "-", "set the database name")return cmd
}

新版本修改如下：

根据命令参数长度补齐：

// rpad adds padding to the right of a string.
func rpad(s string, padding int) string {template := fmt.Sprintf("%%-%ds", padding)return fmt.Sprintf(template, s)
}func GetHelpInfo(theCmd []conf.UserCmdFunc) (ret string) {ret = fmt.Sprintf("Available Commands:\n");for _, item := range theCmd {nameLen := len(item.Name)if nameLen > cmdMaxLen {cmdMaxLen = nameLen}}for _, item := range theCmd {ret += fmt.Sprintf("  %v %v\n", rpad(item.Name, cmdMaxLen), item.ShortHelp)}return
}

子命令实现：


var mode intfunc NewCmdTest() *cobra.Command{var cmd = &cobra.Command{Use:     name,Short:   shortDescription,Long:    longDescription + "\n" + common.GetHelpInfo(theCmd),Example: example,RunE: func(cmd *cobra.Command, args []string) error {// 1 没有参数if (len(args) == 0) {//klog.Warning("no args found")//common.PrintHelpInfo(theCmd)cmd.Help()return nil}// 2 遍历是否有合法的参数，如无则提示idx := -1for idx1, item := range theCmd {if (args[0] == item.Name) {idx = idx1 // why ???break}}if idx == -1 {klog.Printf("arg '%v' not support", args[0])cmd.Help()return nil}// 3 执行公共的初始化klog.Printf("bussiness init, mode: %v\n", mode) // just test// 4 执行命令theCmd[idx].Func(args)return nil},}// note：使用子命令形式，下列可在help中展开// 命令参数，保存的值，参数名，默认参数，说明cmd.Flags().IntVarP(&mode, "mode", "m", 0, "set the test mode")return cmd
}
Longcmd.Help()

测试

默认输出帮助信息：

$ ./cmdtool.execmd test tool.【中文样例】命令终端测试示例工具。Usage:cmdtool.exe [command]Examples:comming soon...Available Commands:db          db commandhelp        Help about any commandmisc        misc commandtest        test commandFlags:-c, --config string   config file (config.yaml)-h, --help            help for cmdtool.exe-o, --output string   specify the output file name-p, --print           verbose output--version         version for cmdtool.exeUse "cmdtool.exe [command] --help" for more information about a command.

执行子命令，默认将合法的命令输出：

$ ./cmdtool.exe test
[2020-12-11 14:51:24.009 rootCmd.go:115] helloooooo 100s firstblood
test...Available Commands:foo   just a foo help infowatch watch config fileUsage:cmdtool.exe test [flags]Examples:example comming up...Flags:-h, --help       help for test-m, --mode int   set the test modeGlobal Flags:-c, --config string   config file (config.yaml)-o, --output string   specify the output file name-p, --print           verbose output$ ./cmdtool.exe test nocmd
[2020-12-11 14:53:13.301 rootCmd.go:115] helloooooo 100s firstblood
[2020-12-11 14:53:13.303 cmd.go:60] arg 'nocmd' not support
test...Available Commands:foo   just a foo help infowatch watch config fileUsage:cmdtool.exe test [flags]Examples:example comming up...Flags:-h, --help       help for test-m, --mode int   set the test modeGlobal Flags:-c, --config string   config file (config.yaml)-o, --output string   specify the output file name-p, --print           verbose output

源码

源码在此。