go-convert

Convert a value into another type.

go get -u github.com/Eun/go-convert

Usage

package main

import (
	"fmt"

	"github.com/Eun/go-convert"
)

func main() {
	// convert a int to a string
	var s string
	convert.MustConvert(1, &s)
	fmt.Printf("%s\n", s)

	// convert a map into a struct
	type User struct {
		ID   int
		Name string
	}
	var u User
	convert.MustConvert(map[string]string{
		"Name": "Joe",
		"ID":   "10",
	}, &u)
	fmt.Printf("%#v\n", u)

	// convert Id to int and Groups to []int and keep the rest
	m := map[string]interface{}{
		"Id":     0,
		"Groups": []int{},
	}
	// convert a map into well defined map
	convert.MustConvert(
		map[string]interface{}{
			"Id":      "1",
			"Name":    "Joe",
			"Groups":  []string{"3", "6"},
			"Country": "US",
		},
		&m,
	)
	fmt.Printf("%v\n", m)

	// convert a interface slice into well defined interface slice
	// making the first one an integer, the second a string and the third an float
	sl := []interface{}{0, "", 0.0}
	convert.MustConvert([]string{"1", "2", "3"}, &sl)
	fmt.Printf("%v\n", sl)
}

Recipe system

go-convert uses a recipe system that defines how and which types should be converted in which type. A lot of recipes are already builtin (see recipes.go), however you can add your own or overwrite the builtin ones.

package main

import (
	"fmt"
	"strings"

	"github.com/Eun/go-convert"
)

type Roles struct {
	IsAdmin     bool
	IsDeveloper bool
}

type User struct {
	ID    int
	Name  string
	Roles Roles
}

func main() {
	// this is the data we want to convert
	data := map[string]string{
		"id":    "10",
		"Name":  "Joe",
		"roles": "AD", // this user is Admin (A) and Developer (D)
	}

	// create a converter
	conv := convert.New(convert.Options{
		Recipes: convert.MustMakeRecipes(
			// convert string into Roles
			func(_ convert.Converter, in string, out *Roles) error {
				(*out).IsAdmin = false
				(*out).IsDeveloper = false
				if strings.Contains(in, "A") {
					(*out).IsAdmin = true
				}
				if strings.Contains(in, "D") {
					(*out).IsDeveloper = true
				}
				return nil
			},
		),
	})

	var user User
	conv.MustConvert(data, &user)
	// user is now an instance of User
	fmt.Printf("%#v\n", user)
}

Adding inline recipes

You can also add recipes inline by implementing a ConvertRecipes() []Recipe function.
Example:

package main

import (
	"fmt"
	"strings"

	"github.com/Eun/go-convert"
)

type Roles struct {
	IsAdmin     bool
	IsDeveloper bool
}

type User struct {
	ID    int
	Name  string
	Roles Roles
}

func (user *User) ConvertRecipes() []convert.Recipe {
	return convert.MustMakeRecipes(
		// convert string into Roles
		func(_ convert.Converter, in string, out *Roles) error {
			out.IsAdmin = false
			out.IsDeveloper = false
			if strings.Contains(in, "A") {
				out.IsAdmin = true
			}
			if strings.Contains(in, "D") {
				out.IsDeveloper = true
			}
			return nil
		},
	)
}

func main() {
	// this is the data we want to convert
	data := []map[string]string{
		{
			"id":    "10",
			"Name":  "Joe",
			"roles": "AD", // this user is Admin (A) and Developer (D)
		},
		{
			"id":    "21",
			"Name":  "Alice",
			"roles": "D", // this user is Developer (D)
		},
	}

	var users []User
	convert.MustConvert(data, &users)
	// users is now an instance of []User
	fmt.Printf("%#v\n", users)
}

Notice

This library is using reflection so be aware it might be slow in your usecase.