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brink

0.6.2 • Public • Published

brink.js

Data-binding, observers and computed properties in Node and the browser.

How it works.

Data binding works by using Object.defineProperty() to define getters and setters for your properties behind the scenes.

Watchers are not invoked immediately when a property changes, they are automatically debounced. So even if you change a property multiple times in one run loop, the watcher will only be called once (in the next run loop).


Data Binding

Bindings enable you to keep two or more properties in sync. Declare the binding and Brink makes sure that changes get propagated.

 
var a,
    b;
 
= $b.Object.create({
    color : 'green'
});
 
= $b.Object.create({
    color : $b.bindTo(a, 'color')
});
 
console.log(b.color); // 'green'
b.color = 'red';
console.log(a.color); // 'red'
 
a.color = 'blue';
console.log(b.color); // 'blue'
 

You can bind any property of a $b.Object instance to any other property of a $b.Object instance. The $b.bindTo() helper is there during object definition/creation, however you can bind properties at any time:

 
var a,
    b;
 
= $b.Object.create();
= $b.Object.create();
 
a.prop('color').bindTo(b, 'color');
 
a.color = 'green';
 
console.log(b.color); // 'green'
b.color = 'red';
console.log(a.color); // 'red'
 

Observers

You can also set up functions to watch for property changes:

 
var a;
 
= $b.Object.create({
    color : 'green',
 
    init : function () {
        this.watch('color', this.colorChanged.bind(this));
    },
 
    colorChanged : function () {
        console.log(this.color); // red
    }
});
 
a.color = 'red';
 

Computed Properties

Computed properties let you define your own getters and setters for a property:

 
var Person = $b.Object.extend({
 
    firstName : '',
    lastName : '',
    fullName : $b.computed({
 
        watch : ['firstName', 'lastName'],
 
        get : function () {
            return [this.firstName, this.lastName].join(' ');
        },
 
        set : function (val) {
            val = val.split(' ');
            this.firstName = val[0];
            this.lastName = val[1] || '';
            return val.join(' ');
        }
    })
});
 
var person = Person.create({firstName : 'Jane', lastName : 'Smith'});
 
console.log(person.fullName); // 'Jane Smith';
person.fullName = 'John Doe';
console.log(person.firstName, person.lastName); // 'John', 'Doe';
 

An added benefit of computed properties is automatically specifying dependencies on other properties. This means you don't need to write custom watchers to notify Brink a computed property has a new value.

You specify property dependencies by defining a watch property:

 
var A,
    b;
 
A = $b.Object.extend({
 
    prop1 : 1,
    prop2 : 2,
 
    sum : $b.computed({
 
        watch : ['prop1', 'prop2'],
 
        get : function () {
            return this.prop1 + this.prop2;
        }
 
    })
});
 
= A.create();
 
b.prop1 = 5;
b.prop2 = 10;
 
b.watch('sum', function () {
    console.log(b.sum); // 15
});
 

By specifying the watch array, anytime prop1 or prop2 changes, sum will also be marked as dirty and any watchers watching sum will be invoked.


Inheritance

To define a Class, call the extend() method on $b.Class :

 
var Animal = $b.Class.extend({
 
    name : '',
    sound : '???',
 
    say : function (thing) {
        console.log(this.name + ' : ' + thing);
    },
 
    greet : function () {
        this.say(this.sound);
    }
});
 

You can then extend Animal, by using its extend() method :

 
var Dog = Animal.extend({
 
    sound : 'woof',
 
    init : function () {
        console.log(this.name + ' created...');
    },
 
    say : function (thing) {
        this._super(thing + '!');
    }
});
 

You can call this._super() within a method to invoke the Parent class' method.

To create an instance of your Class, call the create() method of your Class. You can pass in property values with an optional object.

If you define an init method on your Class, that method will be invoked during creation.

 
var fido = Dog.create({name : 'Fido'}); // 'Fido created...'
 
fido.greet(); // 'Fido : woof!'
 

Publish/Subscribe

Publish/Subscribe is a very good model for loose-coupling your components. Brink takes it a step further by making it's pub/sub system promise-based.

 
var Publisher = $b.Class.extend({
 
    doSomething : function (someValue){
 
        this.publish('something', 'hello!').then(function (response) {
            console.log(response);
        });
    }
});
 
var Subscriber = $b.Class.extend({
 
    init : function() {
        this.subscribe('something', this.handleSomething);
    },
 
    handleSomething : function (n, message) {
        console.log(message);
        return 'received!';
    }
});
 
var subscriberInstance = Subscriber.create();
var publisherInstance = Publisher.create();
 
publisherInstance.doSomething(); // 'hello!', 'received!'
 

subscribe() takes three arguments. The first two are mandatory, the third is optional. The first, a String, for name of the notification you want to listen for. The second, a function that handles the notification.

The third argument is priority. If you have multiple instances listening for a notification, the lower the priority the sooner an instance will receive the notification.

publish() takes at least one argument. The first argument is the name of the notification you are sending. Subsequent arguments will be passed to all subscribers in order (see message above).

So, where do promises come in? Subscibers can return values or promises, the publisher's then() method will be invoked at the end of the subscriber chain.

If you replace the Subscriber above with the follwing Class, you will see the publishers then() invoked 1 second later.

 
var Subscriber = $b.Class.extend({
 
    init : function() {
        this.subscribe('something', this.handleSomething);
    },
 
    handleSomething : function (n, message) {
 
        console.log(message);
 
        return $b.Q.Promise(function (resolve, reject) {
            setTimeout(function () {
                resolve('received!');
            }, 1000);
        });
    }
});
 
Notifications

Each time a subsciber's listener is invoked it receives a Notification instance as the first argument. You can think of this much like an Event object.

Notifications have two properties that might be of interest to you, name and dispatcher. Use name to get the name of the notification that was sent; this is useful if you have the same method handling multiple notification types. You can use dispatcher to see which instance fired the notification.

Notifications also have a very useful cancel() method. This is much like stopPropagation() for events. When you call cancel() any subscribers later in the chain will not hear about that notification, and the publishers then() will be invoked when the current method returns. If the method returns a promise, the publishers then() will be invoked once the promise is resolved.

 
var Subscriber = $b.Class.extend({
 
    init : function() {
        this.subscribe('something', this.handleSomething);
    },
 
    handleSomething : function (n, message) {
 
        console.log(message);
 
        n.cancel(); // No other subscribers will hear about this notification.
 
        return $b.Q.Promise(function (resolve, reject) {
 
            setTimeout(function () {
                resolve('received!'); // Publisher's `then()` method will be invoked now.
            }, 1000);
 
        });
    }
});
 

Data Layer

Brink's Model, Store and Adapter Classes offer you a flexible and easy way to work with your data layer.

Using Brink.attr(), Brink.belongsTo() and Brink.hasMany() you can define simple or complex model structures.

 
var MyStore = $b.Store.create();
 
var Person = $b.Model.extend({
 
    primaryKey : 'id',
    modelKey : 'person',
 
    adapter : $b.RESTAdapter.create(),
    store : MyStore,
 
    schema : $b.Schema.create({
        firstName : $b.attr(String),
        lastName : $b.attr(String),
 
        children : $b.hasMany('person'),
        spouse : $b.belongsTo('person')
    })
});
 
var dad = Person.create({
    firstName : 'John',
    lastName : 'Doe'
});
 
var mom = Person.create({
    firstName : 'Jane',
    lastName : 'Doe'
});
 
var child1 = Person.create({
    firstName : 'Mary',
    lastName  : 'Doe'
});
 
var child2 = Person.create({
    firstName : 'Bob',
    lastName  : 'Doe'
});
 
dad.spouse = mom;
dad.children.push(child1, child2);
 
$b.Q.all([
    mom.save(),
    child1.save(),
    child2.save()
]).then(function () {
    dad.save();
});
 

Both hasMany() and belongsTo() relationships serialize as the primary key values of the records they represent.

This is why we call save() on the mom and children before we save the dad record, otherwise they would not have primary keys.

The reverse happens when we de-serialize. This means that if we were to do :

 
var dad = Person.create();
dad.deserialize({spouse : '123'});
 
console.log(dad.spouse);
 

dad.spouse would be a Person instance, not the String value we gave it when we deserialized.

If there is a record with that primary key value in the Store, it will be used, however if there is no corresponding record in the store, then a new record will be created with it's primary key set to the correct value.

Thus, expanding on the above, if we wanted to get the name of the spouse we could do :

 
var dad = Person.create();
dad.deserialize({spouse : '123'});
 
function logSpouseName () {
    console.log(dad.spouse.firstName + ' ' + dad.spouse.lastName);    
}
 
if (dad.spouse.isLoaded) {
    logSpouseName();
}
 
else {
    dad.spouse.fetch().then(logSpouseName);
}
 

Brink.attr(), Brink.hasMany() and Brink.belongsTo() all take a second argument of options when you are declaring them.

 
var MyStore = $b.Store.create();
 
var Name = $b.Model.extend({
    primaryKey : null,
    schema : $b.Schema.create({
        firstName  : $b.attr(String, {key : 'first_name', defaultValue : 'John'}),
        lastName  : $b.attr(String, {key : 'last_name', defaultValue : 'Doe'})
    })    
});
 
var Person = $b.Model.extend({
 
    primaryKey : 'id',
    modelKey : 'person',
 
    adapter : $b.RESTAdapter.create(),
    store : MyStore,
 
    schema : $b.Schema.create({
        name  : $b.belongsTo('name', {embedded : true})
    })
});
 

options which apply to all attr(), belongsTo() and hasMany() are key and defaultValue.

defaultValue allows you to specify exactly that, a default value to use for all records created.

key allows you to specify a different property name to use in your model, without affecting the serialization or deserialization of your models.

 
var name = Name.create();
name.deserialize({first_name : 'Bob', last_name : 'Smith'})l
 
console.log(name.firstName); // Bob
console.log(name.lastName); // Smith
 
console.log(name.serialize()); // {first_name : 'Bob', last_name : 'Smith'}
 

hasMany() and belongsTo() relationships have another option they can use, embedded.

Setting embedded to true overrides the default behavior of relationships in that they won't serialize and deserialize as primary keys, instead they will serialize() the whole record nested.

 
var MyStore = $b.Store.create();
 
var Name = $b.Model.extend({
    primaryKey : null,
    schema : $b.Schema.create({
        firstName  : $b.attr(String, {key : 'first_name', defaultValue : 'John'}),
        lastName  : $b.attr(String, {key : 'last_name', defaultValue : 'Doe'})
    })    
});
 
var Person = $b.Model.extend({
 
    primaryKey : 'id',
    modelKey : 'person',
 
    adapter : $b.RESTAdapter.create(),
    store : MyStore,
 
    schema : $b.Schema.create({
        name  : $b.belongsTo('name', {embedded : true})
    })
});
 
var person = Person.create();
person.deserialize({name : {
    first_name : 'Bob',
    last_name : 'Smith'  
}});
 
console.log(person.serialize()); // {name : {first_name : 'Bob', last_name : 'Smith'}}
 

Documentation

Building

Clone this repo, then :

$ cd brink.js
$ npm install
$ node tasks/build

Running Unit Tests

$ npm install
$ node tasks/test

Contributors

License

This software is released under the terms of the MIT License.

(c) 2015 Taka Kojima (the "Author").
All Rights Reserved.

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.

Distributions of all or part of the Software intended to be used
by the recipients as they would use the unmodified Software,
containing modifications that substantially alter, remove, or
disable functionality of the Software, outside of the documented
configuration mechanisms provided by the Software, shall be
modified such that the Author's bug reporting email addresses and
urls are either replaced with the contact information of the
parties responsible for the changes, or removed entirely.

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.

Except where noted, this license applies to any and all software
programs and associated documentation files created by the
Author, when distributed with the Software.

Keywords

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Install

npm i brink

DownloadsWeekly Downloads

10

Version

0.6.2

License

MIT

Last publish

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