structtag

structtag provides an easy way of parsing and manipulating struct tag fields. Please vendor the library as it might change in future versions.

Install

go get github.com/fatih/structtag

Example

package main

import (
    "fmt"
    "reflect"
    "sort"

    "github.com/fatih/structtag"
)

func main() {
    type t struct {
        t string `json:"foo,omitempty,string" xml:"foo"`
    }

    // get field tag
    tag := reflect.TypeOf(t{}).Field(0).Tag

    // ... and start using structtag by parsing the tag
    tags, err := structtag.Parse(string(tag))
    if err != nil {
        panic(err)
    }

    // iterate over all tags
    for _, t := range tags.Tags() {
        fmt.Printf("tag: %+v\n", t)
    }

    // get a single tag
    jsonTag, err := tags.Get("json")
    if err != nil {
        panic(err)
    }
    fmt.Println(jsonTag)         // Output: json:"foo,omitempty,string"
    fmt.Println(jsonTag.Key)     // Output: json
    fmt.Println(jsonTag.Name)    // Output: foo
    fmt.Println(jsonTag.Options) // Output: [omitempty string]

    // change existing tag
    jsonTag.Name = "foo_bar"
    jsonTag.Options = nil
    tags.Set(jsonTag)

    // add new tag
    tags.Set(&structtag.Tag{
        Key:     "hcl",
        Name:    "foo",
        Options: []string{"squash"},
    })

    // print the tags
    fmt.Println(tags) // Output: json:"foo_bar" xml:"foo" hcl:"foo,squash"

    // sort tags according to keys
    sort.Sort(tags)
    fmt.Println(tags) // Output: hcl:"foo,squash" json:"foo_bar" xml:"foo"
}