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Add explanation for viper.BindPflag in README.md
Fix #429 /cc @deltaskelta
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1 changed files with 51 additions and 3 deletions
54
README.md
54
README.md
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@ -276,7 +276,6 @@ You will optionally provide additional commands as you see fit.
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The root command represents your binary itself.
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#### Manually create rootCmd
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Cobra doesn't require any special constructors. Simply create your commands.
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@ -298,9 +297,18 @@ var RootCmd = &cobra.Command{
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You will additionally define flags and handle configuration in your init() function.
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for example cmd/root.go:
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For example cmd/root.go:
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```go
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import (
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"fmt"
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"os"
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homedir "github.com/mitchellh/go-homedir"
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"github.com/spf13/cobra"
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"github.com/spf13/viper"
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)
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func init() {
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cobra.OnInitialize(initConfig)
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RootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.cobra.yaml)")
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@ -314,6 +322,30 @@ func init() {
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viper.SetDefault("author", "NAME HERE <EMAIL ADDRESS>")
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viper.SetDefault("license", "apache")
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}
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func main() {
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// Don't forget to read config either from cfgFile or from home directory!
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if cfgFile != "" {
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// Use config file from the flag.
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viper.SetConfigFile(cfgFile)
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} else {
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// Find home directory.
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home, err := homedir.Dir()
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if err != nil {
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fmt.Println(home)
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os.Exit(1)
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}
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// Search config in home directory with name ".cobra" (without extension).
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viper.AddConfigPath(home)
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viper.SetConfigName(".cobra")
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}
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if err := viper.ReadInConfig(); err != nil {
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fmt.Println("Can't read config:", err)
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os.Exit(1)
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}
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}
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```
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### Create your main.go
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@ -341,7 +373,6 @@ func main() {
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}
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```
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### Create additional commands
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Additional commands can be defined and typically are each given their own file
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@ -431,6 +462,23 @@ A flag can also be assigned locally which will only apply to that specific comma
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RootCmd.Flags().StringVarP(&Source, "source", "s", "", "Source directory to read from")
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```
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### Bind Flags with Config
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You can also bind your flags with [viper](https://github.com/spf13/viper):
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```go
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var author string
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func init() {
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RootCmd.PersistentFlags().StringVar(&author, "author", "YOUR NAME", "Author name for copyright attribution")
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viper.BindPFlag("author", RootCmd.PersistentFlags().Lookup("author"))
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}
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```
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In this example the persistent flag `author` is bound with `viper`.
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**Note**, that the variable `author` will not be set to the value from config,
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when the `--author` flag is not provided by user.
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More in [viper documentation](https://github.com/spf13/viper#working-with-flags).
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## Example
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