How to define an enumeration with ember-model

Question

In my ember-model model I need to set a String attribute from an enumeration. Is it possible with ember-model?

By Example I would like to have a Book model:

App.Book({
    id: Ember.attr(),
    title: Ember.attr( 'String' ),
    author: Ember.attr( 'String' ),
    status: App.BookStatus
});

and App.Book.Status as an enum with 3 possible values "FREE", "BORROW", "LOST" and use it:

var myBook = App.Book.create({
    title:'myBook', 
    author:'fred', 
    status: App.BookStatus.FREE
})

I need the equivalent to the Java Enum feature

public enum BookStatus {
    FREE, BORROW, LOST 
}

class Book {
    BookStatus bookStatus;
}

Book bookInstance = new Book();
bookInstance.bookStatus=BookStatus.LOST;

score 6 · Accepted Answer · edited Jun 20 '20 at 09:12

As stated in the docs:

In Ember.js, an Enumerable is any object that contains a number of child objects, and which allows you to work with those children using the Ember.Enumerable API.

So for example:

var players = ["Alex", "Paul", "Tom"];

players.forEach(function(item, index) {
  console.log('Player %@: %@'.fmt(index+1, item));
});

Would output:

// Player 1: Alex
// Player 2: Paul
// Player 3: Tom

To make your own custom class enumerable, you need two items:

To make your own enumerable class/object in ember you could use the Ember.Enumerable mixin and follow this two requirements:

You must have a length property. This property should change whenever the number of items in your enumerable object changes. If you using this with an Ember.Object subclass, you should be sure to change the length property using the built-in set() method.
If you must implement nextObject().

Once you have these two methods implemented, apply the Ember.Enumerable mixin to your class and you will be able to enumerate the contents of your object like any other collection.

Pseudo code:

App.MyEnumObject = Ember.Object.extend(Ember.Enumerable, {
  length: 0,
  nextObject: function() {
    //return the next object of the enumeration
  }
  //more methods and properties
});

See here for more info on enumerable in ember.

Hope it helps.

Edit

Since we are using javascript, what you are trying to do could be done in a much simpler way. For example:

App.bookStatus = {
  FREE: "FREE",
  BORROW: "BORROW",
  LOST: "LOST"
}
  
var myBook = App.Book.create({id: 1, title: 'myBook', author: 'fred', status: App.bookStatus.FREE})

I've updated my question with more details to be certain you get the right understanding. Is your answer still exact with my more detailed question ? — fvisticot, Aug 05 '13 at 21:06
@fvisticot, please see my updated answer, I didn't realize that what you where trying to do could be achieved in a much simpler way since this is javascript land :) — intuitivepixel, Aug 05 '13 at 21:16
Not sure what the question originally asked, but most of this answer is about the Enumberable API, which serves a fairly different purpose than Enums (Enumerations) in Java, C etc. — Gabriel Grant, Feb 01 '17 at 23:31

Gabriel Grant · Answer 2 · 2020-10-29T15:40:46.870

For simple enum's in Ember, just using a simple JavaScript object, as shown at the bottom of @intuitivepixel's answer would suffice, but you can get a bit more functional, Ember-style enums with ember-computed-enum.

It allows getting and setting by more JavaScript-style-friendly names:

myBook.get('status');  // -> 'free'
myBook.set('status', 'lost');
myBook.get('status');  // -> 'lost'
myBook.save();  // -> saves `status: "LOST"` to the server

but also adds enumNameIsValue properties that are particularly useful in templates:

myBook.get('statusIsLost');  // -> true
myBook.get('statusIsFree');  // -> false

Install with ember install ember-computed-enum, then usage is pretty simple

Assuming your model looks something like:

// app/models/book.js

import DS from 'ember-data';

export default DS.Model.extend({
  title: DS.attr('string'),
  author: DS.attr('string'),
  statusCode: DS.attr('string')
});

Where statusCode is returned from the server as one of "FREE", "BORROW", or "LOST"

You would add a mixin-style Ember enum like this:

// app/models/book.js

import DS from 'ember-data';
import { computedEnumMixin } from 'ember-computed-enum';

BOOK_STATUS_ENUM = {
  free: "FREE",
  borrow: "BORROW",
  lost: "LOST"
};

export default DS.Model.extend(
  computedEnumMixin('status', 'statusCode', BOOK_STATUS_ENUM),
  {
  title: DS.attr('string'),
  author: DS.attr('string'),
  statusCode: DS.attr('string')
});

If you're not able to change the name of the status field to statusCode in the API, and still want to use the name status to access the value within your code, you can remap the model field name using a serializer:

// app/serializers/book.js

import DS from 'ember-data';

export default DS.JSONAPISerializer.extend({
  attrs: {
    statusCode: 'status'  // map the API's "status" field to the "statusCode" field on the model
  }
});

Note: I've made the examples to reflect current (Feb 2017) ember-cli conventions, rather than the older globals style of the question

As a small correction, I think your last codeblock should actually say `computedEnumMixin('statusCode', 'status', BOOK_STATUS_ENUM),`, and it should be `status: DS.attr('string')`. As it is, the serialization of the model you've presented would be slightly different than OP's original `App.Book`, which had a `.status` attribute, not a `.statusCode` attribute. — Belden, Oct 28 '20 at 19:10
@Belden thanks for the note. Instead of just flipping `status` and `statusCode`, I've added a section on [remapping the field name with a serializer](https://github.com/gabrielgrant/ember-computed-enum/#re-using-the-existing-attribute-name) so the API can remain unchanged, while still accessing a `status` field on the model object. Does that address the concern you had? — Gabriel Grant, Oct 29 '20 at 15:43

How to define an enumeration with ember-model

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