We often need tools that help us work with optional values. For example, for optional fields in requests/responses from APIs (JSON), optional values in YAML/JSON configs, or nullable columns in some tables. Typically, we use a pointer for certain data types, but this does not work well for some scenarios.
This package offers a simple way to define optional fields and provides some helpers for marshalling and unmarshalling data.
- JSON marshal/unmarshal
- YAML marshal/unmarshal
- SQL driver value/scan
- Useful functions to create and handle optional values
go get -u github.com/kazhuravlev/optionalpackage main
import (
"fmt"
"encoding/json"
"github.com/kazhuravlev/optional"
)
type User struct {
AvatarURL optional.Val[string] `json:"avatar_url"`
// some fields...
}
func main() {
req := []byte(`{"avatar_url": "https://example.com/img.webp"}`)
var user User
if err := json.Unmarshal(req, &user); err != nil {
panic(err)
}
// Check the presence of value and use it.
if avatar, ok := user.AvatarURL.Get(); ok {
fmt.Println("User have avatar", avatar)
} else {
fmt.Println("User have no avatar")
}
// Just check that value presented.
if !user.AvatarURL.HasVal() {
fmt.Println("User have no avatar")
}
// Use default value in case of it did not presented.
fmt.Println("Avatar of this user is:", user.AvatarURL.ValDefault("https://example.com/default.webp"))
// Use this api to adapt value to pointer. It will return nil when value not provided.
avatarPtr := user.AvatarURL.AsPointer()
fmt.Printf("Pointer to avatar: %#v\n", avatarPtr)
}