Ember Data 2.0 Serializer:

In Ember Data a Serializer is used to serialize and deserialize records when they are transferred in and out of an external source. This process involves normalizing property names, transforming attribute values and serializing relationships.

By default, Ember Data uses and recommends the JSONAPISerializer.

JSONSerializer is useful for simpler or legacy backends that may not support the http://jsonapi.org/ spec.

For example, given the following User model and JSON payload:

import DS from 'ember-data';

export default DS.Model.extend({
  friends: DS.hasMany('user'),
  house: DS.belongsTo('location'),

  name: DS.attr('string')
});

{
  id: 1,
  name: 'Sebastian',
  friends: [3, 4],
  links: {
    house: '/houses/lefkada'
  }
}

JSONSerializer will normalize the JSON payload to the JSON API format that the Ember Data store expects.

You can customize how JSONSerializer processes its payload by passing options in the attrs hash or by subclassing the JSONSerializer and overriding hooks:

• To customize how a single record is normalized, use the normalize hook.
• To customize how JSONSerializer normalizes the whole server response, use the normalizeResponse hook.
• To customize how JSONSerializer normalizes a specific response from the server, use one of the many specific normalizeResponse hooks.
• To customize how JSONSerializer normalizes your id, attributes or relationships, use the extractId, extractAttributes and extractRelationships hooks.

The JSONSerializer normalization process follows these steps:

• normalizeResponse - entry method to the serializer.
• normalizeCreateRecordResponse - a normalizeResponse for a specific operation is called.
• normalizeSingleResponse|normalizeArrayResponse - for methods like createRecord we expect a single record back, while for methods like findAll we expect multiple methods back.
• normalize - normalizeArray iterates and calls normalize for each of its records while normalizeSingle calls it once. This is the method you most likely want to subclass.
• extractId | extractAttributes | extractRelationships - normalize delegates to these methods to turn the record payload into the JSON API format.

Check attrs.key.serialize property to inform if the key can be serialized

Looks up the property key that was set by the custom attr mapping passed to the serializer.

When attrs.key.serialize is set to true then it takes priority over the other checks and the related attribute/relationship will be serialized

Check if the given hasMany relationship should be serialized

Given a subclass of DS.Model and a JSON object this method will iterate through each attribute of the DS.Model and invoke the DS.Transform#deserialize method on the matching property of the JSON object. This method is typically called after the serializer's normalize method.

Returns the resource's attributes formatted as a JSON-API "attributes object".

http://jsonapi.org/format/#document-resource-object-attributes

extractErrors is used to extract model errors when a call to DS.Model#save fails with an InvalidError. By default Ember Data expects error information to be located on the errors property of the payload object.

This serializer expects this errors object to be an Array similar to the following, compliant with the JSON-API specification:

{
  "errors": [
    {
      "detail": "This username is already taken!",
      "source": {
        "pointer": "data/attributes/username"
      }
    }, {
      "detail": "Doesn't look like a valid email.",
      "source": {
        "pointer": "data/attributes/email"
      }
    }
  ]
}

The key detail provides a textual description of the problem. Alternatively, the key title can be used for the same purpose.

The nested keys source.pointer detail which specific element of the request data was invalid.

Note that JSON-API also allows for object-level errors to be placed in an object with pointer data, signifying that the problem cannot be traced to a specific attribute:

{
  "errors": [
    {
      "detail": "Some generic non property error message",
      "source": {
        "pointer": "data"
      }
    }
  ]
}

When turn into a DS.Errors object, you can read these errors through the property base:

{{#each model.errors.base as |error|}}
  <div class="error">
    {{error.message}}
  </div>
{{/each}}

Example of alternative implementation, overriding the default behavior to deal with a different format of errors:

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  extractErrors: function(store, typeClass, payload, id) {
    if (payload && typeof payload === 'object' && payload._problems) {
      payload = payload._problems;
      this.normalizeErrors(typeClass, payload);
    }
    return payload;
  }
});

Returns the resource's ID.

extractMeta is used to deserialize any meta information in the adapter payload. By default Ember Data expects meta information to be located on the meta property of the payload object.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  extractMeta: function(store, typeClass, payload) {
    if (payload && payload.hasOwnProperty('_pagination')) {
      let meta = payload._pagination;
      delete payload._pagination;
      return meta;
    }
  }
});

Returns a polymorphic relationship formatted as a JSON-API "relationship object".

http://jsonapi.org/format/#document-resource-object-relationships

relationshipOptions is a hash which contains more information about the polymorphic relationship which should be extracted: - resourceHash complete hash of the resource the relationship should be extracted from - relationshipKey key under which the value for the relationship is extracted from the resourceHash - relationshipMeta meta information about the relationship

Returns a relationship formatted as a JSON-API "relationship object".

http://jsonapi.org/format/#document-resource-object-relationships

Returns the resource's relationships formatted as a JSON-API "relationships object".

http://jsonapi.org/format/#document-resource-object-relationships

keyForAttribute can be used to define rules for how to convert an attribute name in your model to a key in your JSON.

Example

import DS from 'ember-data';

export default DS.RESTSerializer.extend({
  keyForAttribute: function(attr, method) {
    return Ember.String.underscore(attr).toUpperCase();
  }
});

keyForLink can be used to define a custom key when deserializing link properties.

keyForRelationship can be used to define a custom key when serializing and deserializing relationship properties. By default JSONSerializer does not provide an implementation of this method.

Example

 import DS from 'ember-data';

 export default DS.JSONSerializer.extend({
   keyForRelationship: function(key, relationship, method) {
     return 'rel_' + Ember.String.underscore(key);
   }
 });

Normalizes a part of the JSON payload returned by the server. You should override this method, munge the hash and call super if you have generic normalization to do.

It takes the type of the record that is being normalized (as a DS.Model class), the property where the hash was originally found, and the hash to normalize.

You can use this method, for example, to normalize underscored keys to camelized or other general-purpose normalizations.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  normalize: function(typeClass, hash) {
    var fields = Ember.get(typeClass, 'fields');
    fields.forEach(function(field) {
      var payloadField = Ember.String.underscore(field);
      if (field === payloadField) { return; }

      hash[field] = hash[payloadField];
      delete hash[payloadField];
    });
    return this._super.apply(this, arguments);
  }
});

The normalizeResponse method is used to normalize a payload from the server to a JSON-API Document.

http://jsonapi.org/format/#document-structure

This method delegates to a more specific normalize method based on the requestType.

To override this method with a custom one, make sure to call return this._super(store, primaryModelClass, payload, id, requestType) with your pre-processed data.

Here's an example of using normalizeResponse manually:

socket.on('message', function(message) {
  var data = message.data;
  var modelClass = store.modelFor(data.modelName);
  var serializer = store.serializerFor(data.modelName);
  var normalized = serializer.normalizeSingleResponse(store, modelClass, data, data.id);

  store.push(normalized);
});

Called when a record is saved in order to convert the record into JSON.

By default, it creates a JSON object with a key for each attribute and belongsTo relationship.

For example, consider this model:

import DS from 'ember-data';

export default DS.Model.extend({
  title: DS.attr(),
  body: DS.attr(),

  author: DS.belongsTo('user')
});

The default serialization would create a JSON object like:

{
  "title": "Rails is unagi",
  "body": "Rails? Omakase? O_O",
  "author": 12
}

By default, attributes are passed through as-is, unless you specified an attribute type (DS.attr('date')). If you specify a transform, the JavaScript value will be serialized when inserted into the JSON hash.

By default, belongs-to relationships are converted into IDs when inserted into the JSON hash.

IDs

serialize takes an options hash with a single option: includeId. If this option is true, serialize will, by default include the ID in the JSON object it builds.

The adapter passes in includeId: true when serializing a record for createRecord, but not for updateRecord.

Customization

Your server may expect a different JSON format than the built-in serialization format.

In that case, you can implement serialize yourself and return a JSON hash of your choosing.

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serialize: function(snapshot, options) {
    var json = {
      POST_TTL: snapshot.attr('title'),
      POST_BDY: snapshot.attr('body'),
      POST_CMS: snapshot.hasMany('comments', { ids: true })
    }

    if (options.includeId) {
      json.POST_ID_ = snapshot.id;
    }

    return json;
  }
});

Customizing an App-Wide Serializer

If you want to define a serializer for your entire application, you'll probably want to use eachAttribute and eachRelationship on the record.

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serialize: function(snapshot, options) {
    var json = {};

    snapshot.eachAttribute(function(name) {
      json[serverAttributeName(name)] = snapshot.attr(name);
    })

    snapshot.eachRelationship(function(name, relationship) {
      if (relationship.kind === 'hasMany') {
        json[serverHasManyName(name)] = snapshot.hasMany(name, { ids: true });
      }
    });

    if (options.includeId) {
      json.ID_ = snapshot.id;
    }

    return json;
  }
});

function serverAttributeName(attribute) {
  return attribute.underscore().toUpperCase();
}

function serverHasManyName(name) {
  return serverAttributeName(name.singularize()) + "_IDS";
}

This serializer will generate JSON that looks like this:

{
  "TITLE": "Rails is omakase",
  "BODY": "Yep. Omakase.",
  "COMMENT_IDS": [ 1, 2, 3 ]
}

Tweaking the Default JSON

If you just want to do some small tweaks on the default JSON, you can call super first and make the tweaks on the returned JSON.

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serialize: function(snapshot, options) {
    var json = this._super.apply(this, arguments);

    json.subject = json.title;
    delete json.title;

    return json;
  }
});

serializeAttribute can be used to customize how DS.attr properties are serialized

For example if you wanted to ensure all your attributes were always serialized as properties on an attributes object you could write:

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serializeAttribute: function(snapshot, json, key, attributes) {
    json.attributes = json.attributes || {};
    this._super(snapshot, json.attributes, key, attributes);
  }
});

serializeBelongsTo can be used to customize how DS.belongsTo properties are serialized.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serializeBelongsTo: function(snapshot, json, relationship) {
    var key = relationship.key;

    var belongsTo = snapshot.belongsTo(key);

    key = this.keyForRelationship ? this.keyForRelationship(key, "belongsTo", "serialize") : key;

    json[key] = Ember.isNone(belongsTo) ? belongsTo : belongsTo.record.toJSON();
  }
});

serializeHasMany can be used to customize how DS.hasMany properties are serialized.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serializeHasMany: function(snapshot, json, relationship) {
    var key = relationship.key;
    if (key === 'comments') {
      return;
    } else {
      this._super.apply(this, arguments);
    }
  }
});

serializeId can be used to customize how id is serialized For example, your server may expect integer datatype of id

By default the snapshot's id (String) is set on the json hash via json[primaryKey] = snapshot.id.

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
serializeId(snapshot, json, primaryKey) {
    var id = snapshot.id;
    json[primaryKey] = parseInt(id, 10);
  }
});

You can use this method to customize how a serialized record is added to the complete JSON hash to be sent to the server. By default the JSON Serializer does not namespace the payload and just sends the raw serialized JSON object. If your server expects namespaced keys, you should consider using the RESTSerializer. Otherwise you can override this method to customize how the record is added to the hash. The hash property should be modified by reference.

For example, your server may expect underscored root objects.

import DS from 'ember-data';

export default DS.RESTSerializer.extend({
  serializeIntoHash: function(data, type, snapshot, options) {
    var root = Ember.String.decamelize(type.modelName);
    data[root] = this.serialize(snapshot, options);
  }
});

You can use this method to customize how polymorphic objects are serialized. Objects are considered to be polymorphic if { polymorphic: true } is pass as the second argument to the DS.belongsTo function.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  serializePolymorphicType: function(snapshot, json, relationship) {
    var key = relationship.key,
        belongsTo = snapshot.belongsTo(key);
    key = this.keyForAttribute ? this.keyForAttribute(key, "serialize") : key;

    if (Ember.isNone(belongsTo)) {
      json[key + "_type"] = null;
    } else {
      json[key + "_type"] = belongsTo.modelName;
    }
  }
});

Check if the given hasMany relationship should be serialized

The attrs object can be used to declare a simple mapping between property names on DS.Model records and payload keys in the serialized JSON object representing the record. An object with the property key can also be used to designate the attribute's key on the response payload.

Example

import DS from 'ember-data';

export default DS.Model.extend({
  firstName: DS.attr('string'),
  lastName: DS.attr('string'),
  occupation: DS.attr('string'),
  admin: DS.attr('boolean')
});

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  attrs: {
    admin: 'is_admin',
    occupation: { key: 'career' }
  }
});

You can also remove attributes by setting the serialize key to false in your mapping object.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  attrs: {
    admin: { serialize: false },
    occupation: { key: 'career' }
  }
});

When serialized:

{
  "firstName": "Harry",
  "lastName": "Houdini",
  "career": "magician"
}

Note that the admin is now not included in the payload.

The primaryKey is used when serializing and deserializing data. Ember Data always uses the id property to store the id of the record. The external source may not always follow this convention. In these cases it is useful to override the primaryKey property to match the primaryKey of your external store.

Example

import DS from 'ember-data';

export default DS.JSONSerializer.extend({
  primaryKey: '_id'
});