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138 lines
3.4 KiB
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138 lines
3.4 KiB
Markdown
[Back to Guides](../README.md)
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# How to add relationship links
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ActiveModelSerializers offers you many ways to add links in your JSON, depending on your needs.
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The most common use case for links is supporting nested resources.
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The following examples are without included relationship data (`include` param is empty),
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specifically the following Rails controller was used for these examples:
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```ruby
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class Api::V1::UsersController < ApplicationController
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def show
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render jsonapi: User.find(params[:id]),
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serializer: Api::V1::UserSerializer,
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include: []
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end
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```
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Bear in mind though that ActiveModelSerializers are [framework-agnostic](outside_controller_use.md), Rails is just a common example here.
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### Links as an attribute of a resource
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**This is applicable to JSONAPI, JSON and Attributes adapters**
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You can define an attribute in the resource, named `links`.
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```ruby
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class Api::V1::UserSerializer < ActiveModel::Serializer
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attributes :id, :name, :links
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def links
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{
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self: api_v1_user_path(object.id),
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microposts: api_v1_microposts_path(user_id: object.id)
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}
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end
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end
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```
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This will resilt in (example is in jsonapi adapter):
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```json
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{
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"data": {
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"id": "1",
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"type": "users",
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"attributes": {
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"name": "Example User",
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"links": {
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"self": "/api/v1/users/1",
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"microposts": "/api/v1/microposts?user_id=1"
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}
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}
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}
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}
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```
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### Links as a property of the resource definiton
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**This is only applicable to JSONAPI adapter**
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You can use the `links` class method to define the links you need in the resource's primary data.
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```ruby
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class Api::V1::UserSerializer < ActiveModel::Serializer
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attributes :id, :name
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link(:self) { api_v1_user_path(object.id) }
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link(:microposts) { api_v1_microposts_path(user_id: object.id) }
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end
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```
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This will resilt in (example is in jsonapi adapter):
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```json
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{
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"data": {
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"id": "1",
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"type": "users",
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"attributes": {
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"name": "Example User"
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},
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"links": {
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"self": "/api/v1/users/1",
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"microposts": "/api/v1/microposts?user_id=1"
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}
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}
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}
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```
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### Links that follow the JSONAPI spec
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**This is only applicable to JSONAPI adapter**
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If you have a JSONAPI-strict client that you are working with (like `ember-data`)
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you need to construct the links inside the relationships. Also the link to fetch the
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relationship data must be under the `related` attribute, whereas to manipulate the
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relationship (in case of many-to-many relationship) must be under the `self` attribute.
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You can find more info in the [spec](http://jsonapi.org/format/#document-resource-object-relationships).
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Here is how you can do this:
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```ruby
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class Api::V1::UserSerializer < ActiveModel::Serializer
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attributes :id, :name
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has_many :microposts, serializer: Api::V1::MicropostSerializer do
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link(:related) { api_v1_microposts_path(user_id: object.id) }
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end
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#this is needed to avoid n+1, gem core devs are working to remove this necessity
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#more on: https://github.com/rails-api/active_model_serializers/issues/1325
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def microposts
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object.microposts.loaded ? object.microposts : object.microposts.none
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end
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end
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```
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This will result in:
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```json
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{
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"data": {
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"id": "1",
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"type": "users",
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"attributes": {
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"name": "Example User"
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},
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"relationships": {
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"microposts": {
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"data": [],
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"links": {
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"related": "/api/v1/microposts?user_id=1"
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}
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}
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}
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}
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}
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```
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