Backbone.Rel

Backbone.Rel extends your Backbone models with a lightweight relationships manager.

How does it work? API

Rel

Backbone.Rel exposes a method rel that is a relationship getter.

hasMany

You can implement a hasMany method in a Model to define a relationship. The method must return an object with the relation name as a key and options as a value.

Options:

• collection: You must specify the collection.
• filter: A function that will be used to filter the collection.
• id: The foreign id pointing to your model.

belongsTo

You can implement a belongsTo method in a Model or a Collection to define a relationship. The method must return an object with the relation name as a key and the collection as a value.

If you want to define a belongsTo relationship on a collection you have to store the key on the collection object in your initialize.

Accessing nested relationships, the "monadic" rel getter.

You can pass as many arguments as you want to the rel getter in order to get nested relationships. Any failure on the getter chain will be properly propagated, avoiding TypeError: Cannot call method 'foo' of null.

Accessing attributes inside the relations with relGet

Most of the errors on working with relational data is when a relation is not met and we try to access a attribute of that inexistant model. For instance, we have a task that belong to a project and we want to get that projects name.

task.relGet('project', 'name', 'Unknown project'); // It will show the project name or 'Unkown project'
user.relGet('project.tasks', 'name', []); // It will return all tasks names or []

Invoking methods inside relations

Sometimes we want to invoke a method or access an attribute through a relation. relResult is a wrapper of _.result on a relation.

task.relResult('project', 'fullName', 'Unknown project'); // It will call project.fullName if the relation succeded

Example

// models/project.js
Models.Project.hasMany = function () {
  return {
    users: {collection: Collections.users, id: 'project_id'}
  , tasks: {collection: Collection.tasks, filter: function (task) {
      return task.rel('project') ? task.rel('project').id === this.id : null;
    }}
  };
};
 
// models/user.js
Models.User.hasMany = function () {
  return {
    tasks: {collection: Collections.tasks, id: 'user_id'}
  };
};
 
Models.User.belongsTo = function () {
  return {
    project: Collection.projects
  };
};
 
// models/task.js
Models.Task.belongsTo = function () {
  return {
    user: Collections.users
  , project: function (task) {
      return task.rel('user.project');
    }
  };
};
 
var project = new Project({id: 1})
  , user = new User({id: 1, project_id: 1})
  , task1 = new Task({id: 1, user_id: 1})
  , task2 = new Task({id: 2, user_id: 1});
 
assert.equal(user.rel('tasks').length, 2);
assert.equal(user.rel('project'), project);
assert.equal(task1.rel('user'), user);
assert.equal(task1.rel('project'), project);

Dependencies

Backbone.Rel depends on underscore.inflection.

Tests

You must have node installed in order to run the tests.

npm install
make

License

(The MIT License)

Copyright (c) 2012 Pau Ramon masylum@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.