go-rel/gin-example

package todos

import (
    "encoding/json"
    "errors"
    "fmt"
    "os"
    "time"
)

var (
    // TodoURLPrefix to be returned when encoding todo.
    TodoURLPrefix = os.Getenv("URL") + "todos/"
    // ErrTodoTitleBlank validation error.
    ErrTodoTitleBlank = errors.New("Title can't be blank")
)

// Todo respresent a record stored in todos table.
type Todo struct {
    ID        uint      `json:"id"`
    Title     string    `json:"title"`
    Order     int       `json:"order"`
    Completed bool      `json:"completed"`
    CreatedAt time.Time `json:"created_at"`
    UpdatedAt time.Time `json:"updated_at"`
}

// Validate todo.
func (t Todo) Validate() error {
    var err error
    switch {
    case len(t.Title) == 0:
        err = ErrTodoTitleBlank
    }

    return err
}

// MarshalJSON implement custom marshaller to marshal url.
func (t Todo) MarshalJSON() ([]byte, error) {
    type Alias Todo

    return json.Marshal(struct {
        Alias
        URL string `json:"url"`
    }{
        Alias: Alias(t),
        URL:   fmt.Sprint(TodoURLPrefix, t.ID),
    })
}