structomap

This package helps you to transform your struct into map easily. It provides a structomap.Serializer interface implemented by the structomap.Base type which contains chainable function to add, remove or modify fields. The struct is transformed to a map[string]interface{} using the Transform(entity interface{}) method. It is then up to you to encode the result in JSON, XML or whatever you like.

Here is an example.

import "github.com/danhper/structomap"

type User struct {
    ID        int
    Email     string
    HideEmail bool
    FirstName string
    LastName  string
    CreatedAt time.Time
    UpdatedAt time.Time
}

currentTime := time.Date(2015, 05, 13, 15, 30, 0, 0, time.UTC)

user := User{
    ID: 1, Email: "x@example.com", FirstName: "Foo", LastName:  "Bar",
    HideEmail: true, CreatedAt: currentTime, UpdatedAt: currentTime,
}
userSerializer := structomap.New().
              UseSnakeCase().
              Pick("ID", "FirstName", "LastName", "Email").
              PickFunc(func(t interface{}) interface{} {
                  return t.(time.Time).Format(time.RFC3339)
              }, "CreatedAt", "UpdatedAt").
              OmitIf(func(u interface{}) bool {
                  return u.(User).HideEmail
              }, "Email").
              Add("CurrentTime", time.Date(2015, 5, 15, 17, 41, 0, 0, time.UTC)).
              AddFunc("FullName", func(u interface{}) interface{} {
                  return u.(User).FirstName + " " + u.(User).LastName
              })

userMap := userSerializer.Transform(user)
str, _ := json.MarshalIndent(userMap, "", "  ")
fmt.Println(string(str))

will give:

{
  "created_at": "2015-05-13T15:30:00Z",
  "current_time": "2015-05-15T17:41:00Z",
  "first_name": "Foo",
  "full_name": "Foo Bar",
  "id": 1,
  "last_name": "Bar",
  "updated_at": "2015-05-13T15:30:00Z"
}

Working with slices and arrays

You can also use structomap to transform slices and arrays, it will be applied to all elements. The only thing to do is to call TransformArray(entities) on a slice or an array. As TransformArray expects an interface{}, but in fact really wants a slice or an array, a second error argument is returned. If you do not want it, you can use MustTransformArray, which will panic instead of returning an error.

Here in an example reusing the above serializer.

otherUser := User{ID: 2, FirstName: "Ping", LastName: "Pong", CreatedAt: createdAt, UpdatedAt: createdAt}
users := []User{user, otherUser}
result, _ := userSerializer.TransformArray(users)
str, _ := json.MarshalIndent(result, "", "  ")
fmt.Println(string(str))

This will give:

[
  {
    "created_at": "2015-05-13T15:30:00Z",
    "current_time": "2015-05-15T17:41:00Z",
    "first_name": "Foo",
    "full_name": "Foo Bar",
    "id": 1,
    "last_name": "Bar",
    "updated_at": "2015-05-13T15:30:00Z"
  },
  {
    "created_at": "2015-05-13T15:30:00Z",
    "current_time": "2015-05-15T17:41:00Z",
    "email": "",
    "first_name": "Ping",
    "full_name": "Ping Pong",
    "id": 2,
    "last_name": "Pong",
    "updated_at": "2015-05-13T15:30:00Z"
  }
]

Choosing a key format

You can set the key format for the output map using UseSnakeCase(), UsePascalCase() or UseCamelCase() on the serializer object. You can also set the default case for all new serializers by using structomap.SetDefaultCase(structomap.SnakeCase) (structomap.CamelCase and structomap.PascalCase are also available). The init() function would be a good place to set this.

Building your own serializer

With structomap.Base as a base, you can easily build your serializer.

type UserSerializer struct {
  *structomap.Base
}

func NewUserSerializer() *UserSerializer {
  u := &UserSerializer{structomap.New()}
  u.Pick("ID", "CreatedAt", "UpdatedAt", "DeletedAt")
  return u
}

func (u *UserSerializer) WithPrivateInfo() *UserSerializer {
  u.Pick("Email")
  return u
}

userMap := NewUserSerializer().WithPrivateInfo().Transform(user)

Note that the u.Pick, and all other methods do modify the serializer, they do not return a new serializer each time. This is why it works even when ignoring u.Pick return value.

License

This is released under the MIT license. See the LICENSE file for more information.

Godoc

The full documentation is available at https://godoc.org/github.com/danhper/structomap.