@atlassian/backbone-brace

Backbone.Brace

Brace is an extension to Backbone that adds mixins and self-documenting attributes & events.

Self-documenting attributes and events

Brace allows:

• "namedEvents" on Models, Collections, Views and Routers, which is a collection of exposed events
• "namedAttributes" on Models, which is a collection of exposed attributes - ie a model schema

Both namedEvents and namedAttributes are arrays of strings. namedAttributes can also be an object.

:::javascript
var Person = Brace.Model.extend({
    namedAttributes: ["name"],
    namedEvents: ["sleep"]
});

For each attribute in namedAttributes, get[Attribute] and set[Attribute] methods are generated:

:::javascript
var person = new Person();
person.setName("Tim");
person.getName() // Returns "Tim"

Backbone models' get() and set() validate attributes:

:::javascript
person.get("name"); // ok
person.set("name", "Timmy"); // ok
person.set({
    name: "Timothy"
}); // ok

person.get("lost"); // throws exception
person.set("lost", "frequently"); // throws exception
person.set({
    lost: "frequently"
}); // throws exception

The types of your namedAttributes are validated and coerced when namedAttributes is an object:

:::javascript
var People = Brace.Collection.extend();
var Person = Brace.Model.extend({
    namedAttributes: {
        name : "string", // validate primitives with typeof
        otherNames : [ "string" ], // validate typed array-likes
        birthDate : Date, // validate arbitrary ctors with instanceof,
                          // calls `new ctor(rawValue)` if necessary
        children : People, // validate Backbone.Collections,
                           // coerces arrays and contained models if necessary
        attributes : Array, // validate untyped array-likes
        metadata : null || undefined || false // skip validation completely
    }
});
People.model = Person;

var person = new Person({ name : 'Enigma' }); // ok
person.set('name', null); // ok
person.set('name', 'Nazim'); // ok
person.set('name', 4); // throws exception

person.set('otherNames', [ 'Ahmed' ]); // ok
person.set('otherNames', [ 1, 4 ]); // throws exception

person.set('attributes', [ 'one', 2, {} ]); // ok
person.set('attributes', 'The Dude'); // throws exception

person.set('birthDate', 'Mar 12 1960'); // ok
person.get('birthDate').toString(); // "Sat Mar 12 1960 00:00:00 GMT+1100 (AUS Eastern Daylight Time)"

person.set('children', [ { name : 'Adam' }, { name : 'Mariam' }, { name : 'Sarah' } ]); // ok
person.get('children'); // returns People instance containing three Person models.

For each event in namedEvents, on[Event] and trigger[Event] methods are generated:

:::javascript
person.onSleep(function(dream) { console.log("Dreaming about " + dream); } );
person.triggerSleep("Unicorns");

Mixins

Brace allows a "mixins" property on models, views, collections and routers:

:::javascript
var Loggable = {
    log: function(msg) {
        console.log(msg);
    }
};

var PersonView = Brace.View.extend({
    mixins: [Loggable],
    
    initialize: function() {
        this.log("Initialized");
    }
});

Mixins with Backbone

namedAttributes and namedEvents in mixins are respected:

:::javascript
var Selectable = {
    namedAttributes: ["selected"],
    namedEvents: ["select"],

    initialize: function() {
        this.on("change:selected", _.bind(function(model, selected) {
            if (selected) {
                this.triggerSelect();
            }
        }, this));
    }
};

var Person = Brace.Model.extend({
    mixins: [Selectable]
});

var person = new Person();

person.onSelect(function() { console.log("Person was selected"); });
person.setSelected(true);
person.getSelected();
person.triggerSelect();

Additionally, Brace composes

• initialize() on all objects, and
• defaults and validate() on models

All other name clashes between mixins fail violently and forcefully at class declaration time (not at instance construction time).

:::javascript
var Runnable = {
    run: function() {}
};

var RunModel = Brace.Model.extend({
    mixins: [Runnable],
    run: function() {}
}); // throws "Mixin error: class already has property 'run' defined"