Input and output formats

Goverter supports three different input output format combinations. This guide is for you to decide the formats you want to use.

• interface to struct
• variables to assign-variable
• interface to functions

interface to struct

This is the default when using goverter:converter.

Pros:

• All goverter features are supported
• The interface is usable before goverter generated the implementation.
  • reduces the occurence of compile errors because of missing or outdated generated implementation.
  • allows using generated methods in custom methods

Cons:

• You need to initialize the implementation.
• You need to call methods on the struct to execute conversions

Example (click me)

input.go

package house

import (
	"database/sql"

	"github.com/jmattheis/goverter/example/format/common"
)

// goverter:converter
// goverter:output:format struct
// goverter:extend SQLStringToPString
// goverter:extend ConvertToApartmentMap
type Converter interface {
	ConvertHouse(source common.DBHouse) common.APIHouse
	// goverter:map Owner.Name OwnerName
	ConvertApartment(source common.DBApartment) common.APIApartment
	// goverter:map Name FirstName
	// goverter:ignore Age
	ConvertPerson(source common.DBPerson) common.APIPerson
}

func SQLStringToPString(value sql.NullString) *string {
	if value.Valid {
		return &value.String
	}
	return nil
}

func ConvertToApartmentMap(c Converter, source []common.DBApartment) map[uint]common.APIApartment {
	m := make(map[uint]common.APIApartment)
	for _, apartment := range source {
		m[apartment.Position] = c.ConvertApartment(apartment) // !! this is not supported in some formats
	}
	return m
}

common.go

package common

import "database/sql"

type DBHouse struct {
	Address    string
	Apartments []DBApartment
}

type DBApartment struct {
	Position   uint
	Owner      DBPerson
	CoResident []DBPerson
}

type DBPerson struct {
	ID         int
	Name       string
	MiddleName sql.NullString
	Friends    []DBPerson
	Info       Info
}

type APIHouse struct {
	Address    string
	Apartments map[uint]APIApartment
}

type APIApartment struct {
	Position   uint
	Owner      APIPerson
	OwnerName  string
	CoResident []APIPerson
}

type APIPerson struct {
	ID         int
	MiddleName *string
	FirstName  *string
	Friends    []APIPerson
	Info       Info
	Age        int
}

type Info struct {
	Birthplace string
}

generated/generated.go

// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
//go:build !goverter

package generated

import (
	common "github.com/jmattheis/goverter/example/format/common"
	interfacetostruct "github.com/jmattheis/goverter/example/format/interfacetostruct"
)

type ConverterImpl struct{}

func (c *ConverterImpl) ConvertApartment(source common.DBApartment) common.APIApartment {
	var commonAPIApartment common.APIApartment
	commonAPIApartment.Position = source.Position
	commonAPIApartment.Owner = c.ConvertPerson(source.Owner)
	commonAPIApartment.OwnerName = source.Owner.Name
	if source.CoResident != nil {
		commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
		for i := 0; i < len(source.CoResident); i++ {
			commonAPIApartment.CoResident[i] = c.ConvertPerson(source.CoResident[i])
		}
	}
	return commonAPIApartment
}
func (c *ConverterImpl) ConvertHouse(source common.DBHouse) common.APIHouse {
	var commonAPIHouse common.APIHouse
	commonAPIHouse.Address = source.Address
	commonAPIHouse.Apartments = interfacetostruct.ConvertToApartmentMap(c, source.Apartments)
	return commonAPIHouse
}
func (c *ConverterImpl) ConvertPerson(source common.DBPerson) common.APIPerson {
	var commonAPIPerson common.APIPerson
	commonAPIPerson.ID = source.ID
	commonAPIPerson.MiddleName = interfacetostruct.SQLStringToPString(source.MiddleName)
	pString := source.Name
	commonAPIPerson.FirstName = &pString
	if source.Friends != nil {
		commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
		for i := 0; i < len(source.Friends); i++ {
			commonAPIPerson.Friends[i] = c.ConvertPerson(source.Friends[i])
		}
	}
	commonAPIPerson.Info = c.commonInfoToCommonInfo(source.Info)
	return commonAPIPerson
}
func (c *ConverterImpl) commonInfoToCommonInfo(source common.Info) common.Info {
	var commonInfo common.Info
	commonInfo.Birthplace = source.Birthplace
	return commonInfo
}

variables to assign-variable

This is the default when using goverter:variables.

Pros:

• All goverter features are supported.
• The variables are usable before goverter generated the implementation.
  • reduces the occurence of compile errors because of missing or outdated generated implementation.
  • allows using generated functions in custom methods
• You can execute conversions directly without having to initializing a struct

Cons:

• Possible runtime overhead when Go cannot optimizen variables the same as functions. Benchmark your use-case, if speed is really important to you.

Example (click me)

input.go

package house

import (
	"database/sql"

	"github.com/jmattheis/goverter/example/format/common"
)

// goverter:variables
// goverter:output:format assign-variable
// goverter:extend SQLStringToPString
// goverter:extend ConvertToApartmentMap
var (
	ConvertHouse func(source common.DBHouse) common.APIHouse
	// goverter:map Name FirstName
	// goverter:ignore Age
	ConvertPerson func(source common.DBPerson) common.APIPerson
	// goverter:map Owner.Name OwnerName
	ConvertApartment func(source common.DBApartment) common.APIApartment
)

func SQLStringToPString(value sql.NullString) *string {
	if value.Valid {
		return &value.String
	}
	return nil
}

func ConvertToApartmentMap(source []common.DBApartment) map[uint]common.APIApartment {
	m := make(map[uint]common.APIApartment)
	for _, apartment := range source {
		m[apartment.Position] = ConvertApartment(apartment) // !! this is not supported in some formats
	}
	return m
}

common.go

package common

import "database/sql"

type DBHouse struct {
	Address    string
	Apartments []DBApartment
}

type DBApartment struct {
	Position   uint
	Owner      DBPerson
	CoResident []DBPerson
}

type DBPerson struct {
	ID         int
	Name       string
	MiddleName sql.NullString
	Friends    []DBPerson
	Info       Info
}

type APIHouse struct {
	Address    string
	Apartments map[uint]APIApartment
}

type APIApartment struct {
	Position   uint
	Owner      APIPerson
	OwnerName  string
	CoResident []APIPerson
}

type APIPerson struct {
	ID         int
	MiddleName *string
	FirstName  *string
	Friends    []APIPerson
	Info       Info
	Age        int
}

type Info struct {
	Birthplace string
}

input.gen.go

// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
//go:build !goverter

package house

import common "github.com/jmattheis/goverter/example/format/common"

func init() {
	ConvertApartment = func(source common.DBApartment) common.APIApartment {
		var commonAPIApartment common.APIApartment
		commonAPIApartment.Position = source.Position
		commonAPIApartment.Owner = ConvertPerson(source.Owner)
		commonAPIApartment.OwnerName = source.Owner.Name
		if source.CoResident != nil {
			commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
			for i := 0; i < len(source.CoResident); i++ {
				commonAPIApartment.CoResident[i] = ConvertPerson(source.CoResident[i])
			}
		}
		return commonAPIApartment
	}
	ConvertHouse = func(source common.DBHouse) common.APIHouse {
		var commonAPIHouse common.APIHouse
		commonAPIHouse.Address = source.Address
		commonAPIHouse.Apartments = ConvertToApartmentMap(source.Apartments)
		return commonAPIHouse
	}
	ConvertPerson = func(source common.DBPerson) common.APIPerson {
		var commonAPIPerson common.APIPerson
		commonAPIPerson.ID = source.ID
		commonAPIPerson.MiddleName = SQLStringToPString(source.MiddleName)
		pString := source.Name
		commonAPIPerson.FirstName = &pString
		if source.Friends != nil {
			commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
			for i := 0; i < len(source.Friends); i++ {
				commonAPIPerson.Friends[i] = ConvertPerson(source.Friends[i])
			}
		}
		commonAPIPerson.Info = commonInfoToCommonInfo(source.Info)
		return commonAPIPerson
	}
}
func commonInfoToCommonInfo(source common.Info) common.Info {
	var commonInfo common.Info
	commonInfo.Birthplace = source.Birthplace
	return commonInfo
}

interface to functions

Pros:

• You can execute conversions directly without having to initializing a struct

Cons:

• The interface is only used for defining the conversions and is otherwise not usable
• The use-case map method with converter is unsupported without replacement.

Example (click me)

input.go

package house

import (
	"database/sql"

	"github.com/jmattheis/goverter/example/format/common"
)

// goverter:converter
// goverter:output:format function
// goverter:extend SQLStringToPString
type Converter interface {
	// goverter:map Owner.Name OwnerName
	ConvertApartment(source common.DBApartment) common.APIApartment
	// goverter:map Name FirstName
	// goverter:ignore Age
	ConvertPerson(source common.DBPerson) common.APIPerson
}

func SQLStringToPString(value sql.NullString) *string {
	if value.Valid {
		return &value.String
	}
	return nil
}

common.go

package common

import "database/sql"

type DBHouse struct {
	Address    string
	Apartments []DBApartment
}

type DBApartment struct {
	Position   uint
	Owner      DBPerson
	CoResident []DBPerson
}

type DBPerson struct {
	ID         int
	Name       string
	MiddleName sql.NullString
	Friends    []DBPerson
	Info       Info
}

type APIHouse struct {
	Address    string
	Apartments map[uint]APIApartment
}

type APIApartment struct {
	Position   uint
	Owner      APIPerson
	OwnerName  string
	CoResident []APIPerson
}

type APIPerson struct {
	ID         int
	MiddleName *string
	FirstName  *string
	Friends    []APIPerson
	Info       Info
	Age        int
}

type Info struct {
	Birthplace string
}

generated.go

// Code generated by github.com/jmattheis/goverter, DO NOT EDIT.
//go:build !goverter

package generated

import (
	common "github.com/jmattheis/goverter/example/format/common"
	interfacefunction "github.com/jmattheis/goverter/example/format/interfacefunction"
)

func ConvertApartment(source common.DBApartment) common.APIApartment {
	var commonAPIApartment common.APIApartment
	commonAPIApartment.Position = source.Position
	commonAPIApartment.Owner = ConvertPerson(source.Owner)
	commonAPIApartment.OwnerName = source.Owner.Name
	if source.CoResident != nil {
		commonAPIApartment.CoResident = make([]common.APIPerson, len(source.CoResident))
		for i := 0; i < len(source.CoResident); i++ {
			commonAPIApartment.CoResident[i] = ConvertPerson(source.CoResident[i])
		}
	}
	return commonAPIApartment
}
func ConvertPerson(source common.DBPerson) common.APIPerson {
	var commonAPIPerson common.APIPerson
	commonAPIPerson.ID = source.ID
	commonAPIPerson.MiddleName = interfacefunction.SQLStringToPString(source.MiddleName)
	pString := source.Name
	commonAPIPerson.FirstName = &pString
	if source.Friends != nil {
		commonAPIPerson.Friends = make([]common.APIPerson, len(source.Friends))
		for i := 0; i < len(source.Friends); i++ {
			commonAPIPerson.Friends[i] = ConvertPerson(source.Friends[i])
		}
	}
	commonAPIPerson.Info = commonInfoToCommonInfo(source.Info)
	return commonAPIPerson
}
func commonInfoToCommonInfo(source common.Info) common.Info {
	var commonInfo common.Info
	commonInfo.Birthplace = source.Birthplace
	return commonInfo
}