标志：必须项

必须项

一个必须的（Required）标志，要求终端用户必须在命令行中显式地给出参数值，否则 app 将会拒绝进一步执行。

cmdr 在分析命令行参数的过程中追踪每一标志的命中次数，所以 Required 标志的内部校验算法等价于检查该标志的命中次数是否大于等于 1，是的话则通过，反之则抛出必须项未满足的 exception。

定义一个必须项

.Required() 可以做到。

package main
 
import (
	"context"
	"fmt"
	"os"
 
	"gopkg.in/hedzr/errors.v3"
 
	"github.com/hedzr/cmdr/v2"
	"github.com/hedzr/cmdr/v2/cli"
	"github.com/hedzr/cmdr/v2/examples"
	"github.com/hedzr/is/term/color"
	logz "github.com/hedzr/logg/slog"
)
 
const (
	appName = "required"
	desc    = `a sample to show u what error raised by a missed required flag.`
	version = cmdr.Version
	author  = `The Example Authors`
)
 
func main() {
	app := cmdr.Create(appName, version, author, desc).
		With(func(app cli.App) {
			app.OnAction(func(ctx context.Context, cmd cli.Cmd, args []string) (err error) {
        msg := cmd.Store().MustString("required")
				println(`Hello, World.`, msg)
				return
			})
		}).
		WithBuilders(examples.AddRequiredFlag).
		WithAdders().
		Build()
 
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
 
	if err := app.Run(ctx); err != nil {
		if errors.Is(err, cli.ErrRequiredFlag) {
			fmt.Printf(color.StripLeftTabsC(`
				The <b>REQUIRED</b> Flag not present:
 
				<font color="red">%s</red>
				`),
				err)
			os.Exit(1)
		}
		logz.ErrorContext(ctx, "Application Error:", "err", err) // stacktrace if in debug mode/build
		os.Exit(app.SuggestRetCode())
	} else if rc := app.SuggestRetCode(); rc != 0 {
		os.Exit(rc)
	}
}

运行时

一个运行时未能满足要求的必须项标志的反馈如同这样：

$ go run ./examples/required/
The REQUIRED Flag not present:
 
Flag "Flg{'.required'}" is REQUIRED | cmd=Cmd{''}
$
 
$ go run ./examples/required/ -r xyz
Hello, World. xyz

标志：必须项

必须项

定义一个必须项

运行时

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