Building Stateful Modules with Events and PromisesDOM Manipulation

patrickCAMACHO

Beyond

Friday, June 14, 13

Crashlytics for Android & iOS

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Rails to Backbone.

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What did we have?

ModelBackbone.Model

Backbone.Collection

RoutingBackbone.Router,Backbone.History

ViewsBackbone.Views

EventsBackbone.Events

MV* components

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What’s missing?

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Transitioning Pages to States.

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Piecemeal.

App

State

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Piecemeal.

App

Router

State

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Piecemeal.

App

Router Directors

State

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Piecemeal.

App

Router Directors

State

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Adding a modal.

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Needed better structure.

• Built on single flow and

states

• Modal didn’t fit flow

• Back to the

drawing board

App

Router Directors

State

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Needed better structure.

• Built on single flow and

states

• Modal didn’t fit flow

• Back to the

drawing board

App

Router Directors

State

Settings

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The birth of the “module”.

• Entirely independent pieces of functionality

• It could accept events and start / stop itself

State

this.$('.settings').click(function(){ CLS.Components.Settings.trigger('start');});

Settings

this.$('.overlay').click((function(){ this.trigger('stop');}).bind(this));

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Async behavior.

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Async behavior in states.

• Fetching data, animations, etc

• Want to shut anything down when stopping

Settings

Server

(rendering)

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Promises.

• $.Promises and $.Deferreds

• .done, .fail, .always

• .resolve, .reject

fetch1 = $.get('data.json');fetch2 = $.get('data2.json');

fetch1.done(function(){ console.log(‘success!’); } fetch2.always(function(){ console.log(‘complete!’); }

$.when(fetch1, fetch2).fail(function(){ console.log(‘fail!’); });

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Using with Components.

Settings.start = function() { this.stopDeferred = $.Deferred();

fetch1 = $.get('data.json'); this.stopDeferred.done(fetch1.abort);

fetch2 = $.get('data2.json'); this.stopDeferred.done(fetch2.abort);

$.when(fetch1, fetch2).done(this.render.bind(this));}

Settings.stop = function() { this.stopDeferred.resolve();}

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Good in the short run.

• Only had one application

• Components lived

forever

• Singletons hid the

problems

Settings Alert Center

Real Time Analytics

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Multiple applications.

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Distinct functionality.

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Distinct functionality.

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Multiple applications.

• Lost core assumption of a page-long app

• Apps began to look more and more like modules

Onboarding

Onboarding.start : function(){ if(this._isActive) return; ... this._isActive = true;}

Onboarding.stop : function(){ if(!this._isActive) return; ... this._isActive = false;}

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Multiple applications.

Apps

Router Directors

State

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Persistent functionalty.

• Components needed to be started / stopped by apps on

start / stop

• Not all should be started or stopped

• Back to heavy conditionals

if(nextApp === 'onboard') { CLS.Components.Settings.trigger('stop'); CLS.Components.AlertCenter.trigger('stop');} else if(nextApp === 'logout') { CLS.Components.Settings.trigger('stop'); CLS.Components.AlertCenter.trigger('stop'); CLS.Components.RealTime.trigger('stop');} else if...

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Finding a pattern.

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Same problem, different levels.

• Eventing

• Start

• Stop

• Dependencies

App

State State

Component Component Component

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Isolating knowledge.

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Too many direct references.

• Don’t know outside information

• Clearest in stopping dependencies

if(nextApp === 'onboard') { CLS.Components.Settings.trigger('stop'); CLS.Components.AlertCenter.trigger('stop');} else if(nextApp === 'logout') { CLS.Components.Settings.trigger('stop'); CLS.Components.AlertCenter.trigger('stop'); CLS.Components.RealTime.trigger('stop');} else if...

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Eventing with arguments.

Onboarding Dashboard

Dashboard.start = function() { Onboarding.trigger('stop', this.dependencies);}

Onboarding.stop = function(dependencies) { if(dependencies == null) { dependencies = [] } this.dependencies.forEach(function(dependencies){ if(dependencies.indexOf(dependency) < 0) { dependency.trigger('stop', dependencies); } });}

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• Wanted events, but not the knowledge

Still tightly coupled.

Dashboard.start = function() { Onboarding.trigger('stop', this.dependencies); LoggedOut.trigger('stop', this.dependencies);}

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Simplify functionality.

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Using a vent.

• All of these pieces are using events

• Isolate that functionality to a single unit

Vent

Vent = function() {...}Vent.prototype.on = function() {...}Vent.prototype.one = function() {...}Vent.prototype.off = function() {...}Vent.prototype.trigger = function() {...}

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Sharing a vent.

OnboardingDashboard Vent

Onboarding.start = function() { this.vent.trigger('app:dashboard:stop', this.dependencies); this.vent.trigger('app:loggedOut:stop', this.dependencies);}

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Smart subscriptions.

Dashboard.start = function(vent) { this.vent.trigger('app:onBeforeStart', this.dependencies); this.vent.one('app:onBeforeStart', this.stop.bind(this));}

Onboarding.start = function(vent) { this.vent.trigger('app:onBeforeStart', this.dependencies); this.vent.one('app:onBeforeStart', this.stop.bind(this));}

OnboardingDashboard Vent

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Sharing information.

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• Share data between modules

• Use vent to register responses and request

Synchronous data returns.

VentDashboard Settings

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Dashboard.start = function() { this.currentApplication = ‘foo bar’ this.vent.setResponse( 'current_application', (function(){ return this.currentApplication; }).bind(this); );}

Settings.start = function() { app = this.vent.requestResponse('current_application');}

Synchronous data returns.

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Tying it all together.

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Modularize all the things!

• Isolated functionality

• Start / stop

• Managing dependencies

• Eventing

• Async behavior

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Modularize all the things!

Component

App

State

• Isolated functionality

• Start / stop

• Managing dependencies

• Eventing

• Async behavior

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Vent

Rethinking the flow.

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Vent

Rethinking the flow.

Router

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ComponentsVent

Rethinking the flow.

Apps

Router

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Vent

ComponentsVent

Rethinking the flow.

Apps

Router

States

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Vent

Vent

ComponentsVent

Rethinking the flow.

Apps

Router

States

States

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Making it yours

• Manage complexity and scale

• Isolate functionality into modules

• Manage dependencies

• Allow modules to communicate through a vent

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YOUpatrickCAMACHO

Thank

try.crashlytics.com/jobs

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