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Modelgen hook

Allowing mutation of generated models before rendering
You are looking at the docs for the unreleased master branch. The latest version is v0.11.3.

The following recipe shows how to use a modelgen plugin hook to mutate generated models before they are rendered into a resulting file. This feature has many uses but the example focuses only on inserting ORM-specific tags into generated struct fields. This is a common use case since it allows for better field matching of DB queries and the generated data structure.

First of all, we need to create a function that will mutate the generated model. Then we can attach the function to the plugin and use it like any other plugin.

import (


// Defining mutation function
func mutateHook(b *modelgen.ModelBuild) *modelgen.ModelBuild {
	for _, model := range b.Models {
		for _, field := range model.Fields {
			field.Tag += ` orm_binding:"` + model.Name + `.` +  field.Name + `"`

	return b

func main() {
	cfg, err := config.LoadConfigFromDefaultLocations()
	if err != nil {
		fmt.Fprintln(os.Stderr, "failed to load config", err.Error())

	// Attaching the mutation function onto modelgen plugin
	p := modelgen.Plugin{
		MutateHook: mutateHook,

	err = api.Generate(cfg,
	if err != nil {
		fmt.Fprintln(os.Stderr, err.Error())

Now fields from generated models will contain a additional tag orm_binding.

This schema:

type Object {
    field1: String
    field2: Int

Will gen generated into:

type Object struct {
	field1 *string  `json:"field1" orm_binding:"Object.field1"`
	field2 *int     `json:"field2" orm_binding:"Object.field2"`