tags

README

Tags

An interface package for parsing tags in structs simplifying tag based golang reflections

Usage

Create your custom tag reader simply defining a parser:

func main() {
	obj := Obj{}

	if err := CustomUnmarshaler(&obj); err != nil {
		panic(err)
	}

	if err := CustomScanner(&obj); err != nil {
		panic(err)
	}
}

type Obj struct {
	Val   bool   `customTag:"yourcase"`
	StVal string `customTag:"required"`
}

func CustomUnmarshaler(obj interface{}) error {
	return tags.Parse(obj, `customTag`, func(tagVal string) (string, error) {
		switch tagVal {
		case `yourcase`:
			return `true`, nil
		default:
			return ``, errCustom
		}
	})
}

func CustomScanner(obj interface{}) error {
	return tags.Scan(obj, `customTag`, func(tagVal string, value interface{}) error {
		v, ok := value.(string)
		if !ok {
			return nil
		}

		if tagVal == `required` && v == `` {
			return errRequired
		}

		return nil
	})
}

you get the values of a parent value in the string seperated by a dot:

err := tags.Parse(obj, `tagname`, func(val string) (string, error) {
	allvalues := strings.Split(val, `.`)
	childVal := allvalues[len(allvalues)-1]
	...

Install

Get this package using go get:

$ go get github.com/jobbitz/tags/...

Documentation

Overview

Package tags a simplified golang reflect for your tags.

Usage

Create your custom parser:

func ParseEnv(obj interface{}) error {
	return tags.Parse(obj, `env`, func(tagval string) (string, error) {
		envVar := os.Env(tagval)
		if envVar == `` {
			return ``, fmt.Errorf(`enviroment variable "%s" not found`, tagval)
		}
		return envVar, nil
	})
}

Creating your own scanner:

func ValidateEnum(obj interface{}) error {
	return tags.Scan(obj, `enum`, func(tagval string, propVal interface{}) error {
		validEnums := strings.Split(tagval, `;`)
		actual := fmt.Sprint(propVal)
		for _, enum := range validEnums {
			if actual == enum {
				return nil
			}
		}
		return fmt.Errorf(`Not a valid enum`)
	})
}

Index

• func Parse(obj interface{}, tagname string, parser func(string) (string, error)) error
• func ParseHard(obj interface{}, tagname string, parser func(string) (string, error)) error
• func Scan(obj interface{}, tagname string, scanner func(string, interface{}) error) error

Functions

func Parse

func Parse(obj interface{}, tagname string, parser func(string) (string, error)) error

Parse parses the given tag values using the given parser

func ParseHard

func ParseHard(obj interface{}, tagname string, parser func(string) (string, error)) error

ParseHard parses the giver tag values using the given parser and overrides the previous values

func Scan

func Scan(obj interface{}, tagname string, scanner func(string, interface{}) error) error

Scan gives the given tag value and the value in that stuct property to the given scanner