Inversion of Control and Dependency Injection with Flex using the Parsley Application Framework – Part 2
This is the second part in a series exploring Inversion of Control and Dependency Injection containers available for Flex. In the first part of the series we discussed what IoC and DI are and how they can benefit our applications. In this part, we will explore the Parsley IoC Container through a simple image gallery application.
Here's the source on github...
Inversion of Control and Dependency Injection in Flex using the Parsley Application Framework – Part 1
The Inversion of Control (IoC) design principle and the related Dependency Injection (DI) design pattern have been around for several years. In the Java world, popular frameworks such as Spring make heavy use of these concepts. With the introduction of Actionscript 3 in 2006, the opportunities for framework development increased greatly. As the community matures, we are starting to see robust tools appear on the development landscape. It is a good time to be a Flash geek!
Through this series of articles, we will delve into the Parsley application framework and look at how it implements IoC and DI in the context of a photo slideshow. Through this example we will look at bootstrapping the container, connecting to services, and populating our components with the results. In this first part, we will get an overview of IoC and DI and talk about some of the benefits and drawbacks of using these concepts in our applications.
Piping the Machine: PureMVC Multicore with Pipes and the Finite State Machine (FSM)
This is going to be a walkthrough of making use of PureMVC Multicore (AS3). To help in building a PureMVC Multicore application, we are going to make use of the StateMachine utility for initial setup and configuration as well as the Pipes utility for communication between cores.
Mockups with Balsamiq
We need mockups. They allow us to communicate with developers, clients, users and everybody in between in a common language. I'm a big fan of the Sharpie and a pad of paper. Balsamiq Mockups has created a really great piece of software to speed up the mockup process.
Pleat Menu – Flex Component (draft)
The Pleat menu that is used in Buzzword is really sweet. I wanted to emulate in an attempt to get a reusable component along the same lines. This is the first draft at my attempt, and it admittedly needs some work, but it is still useful, even in its current state.
One of my goals with this is to have all the actual controls in the Pleat available at the top level. This makes it a lot easier to capture in PureMVC (or your event/notification system of choice) and doesn't bury the components. I want to go in and refactor it some more to emulate the Adobe set of Flex components. We'll see if I have the time 
the icons are from the awesome fugue set found here.
The Flickr AS3 API and Flex
We've been using wordpress for our family photo blog for years. It worked well, 4 images in a horizontal scroll. It was kinda tough to navigate though. If you were looking for an image you had to click more... more... more... etc through 3 or 4 years of photos. I wanted something easier to update and navigate. I also wanted to play around with the Flickr API. Luckily the Adobe Flickr AS3 library is very complete. Unfortunately it is very lacking in examples, but the API is well documented so it didn't take too long to get my bearings.
Here's what I came out with. Really it is meant to fill the browser, so check it out here too if you are interested. Source is enabled on the movie. Codes sloppy, but it gets the job done.
So what's up with PureMVC Commands anyway?
That is what Jesse Warden (JesterXL) asks the fine folks over at the PureMVC forums. Cliff gives a good rundown on the why/when/how of PureMVC Commands.
PureMVC's relatively light use of commands, when compared to other widely used MVC frameworks, tends to make one think they are doing something wrong. This isn't really the case. Commands are still viable actors in our applications, but many times the shortest route is the best route. PureMVC doesn't force us to use them, but gives us access when we need to.
I generally use PureMVC Commands for actions that can be initiated from several places, as well as for application startup. I've also found them very useful for popups and AIR window management.
Debugging your AIR/Flex application with Arthropod
Arthropod is an external Debug trace window for Flash/Flex/AIR. Drop a simple class into your project and it will accept logging from the application/swf. I'm using it for debugging around the office with our internal project management AIR application with great success.
Form Validation for the Lazy Programmer in Flex
Forms... Any data-centric application is going to have its fair share of them. They are fairly tedious work. Layout out the form, manage the output, validate the output, over and over. Validation is best when it is active, to let the user know that they have made a mistake before they try to submit the data. Optimally the user won't be allowed to continue until the form data is complete and accurate.
Every form I've written carries the same structure for validation, so as a dedicated lazy programmer I wrote a simple FormValidator class to handle the boilerplate.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 | package com.visualempathy.validators { import flash.display.DisplayObject; import flash.events.EventDispatcher; import flash.events.IEventDispatcher; import mx.events.ValidationResultEvent; import mx.validators.Validator; [Bindable] public class FormValidator extends EventDispatcher { public var formIsValid:Boolean = false; public var validators:Array; private var focusedFormControl:DisplayObject; public function FormValidator(target:IEventDispatcher=null) { super(target); } public function validateForm(event:Event):void { focusedFormControl = event.target as DisplayObject; formIsValid = true; for each( var validator:Validator in validators ) validate(validator); } private function validate(validator:Validator):Boolean { var validatorSource:DisplayObject = validator.source as DisplayObject; var supressEvents:Boolean = validatorSource != focusedFormControl; var event:ValidationResultEvent = validator.validate(null, supressEvents) var currentControlIsValid:Boolean = event.type == ValidationResultEvent.VALID; formIsValid = formIsValid && currentControlIsValid; return currentControlIsValid; } } } |
in the MXML I add an Array structure to hold the Validators, and add the FormValidator like so:
1 2 3 4 5 6 7 8 9 10 | <mx:Array id="validators"> <mx:StringValidator id="studioNameValidator" source="{this.studioNameInput}" property="text" required="true"/> <mx:EmailValidator id="emailValidator" source="{this.emailInput}" property="text" required="true"/> <mx:PhoneNumberValidator id="phoneValidator" source="{this.phoneInput}" property="text" required="true"/> <mx:StringValidator id="addValidator" source="{this.addressInput}" property="text" required="true"/> <mx:StringValidator id="cityValidator" source="{this.cityInput}" property="text" required="true"/> <mx:StringValidator id="stateValidator" source="{this.stateInput}" minLength="2" maxLength="2" property="text" required="true"/> <mx:ZipCodeValidator id="zipcodeValidator" source="{this.zipcodeInput}" property="text" required="true"/> </mx:Array> <validators:FormValidator id="formValidator" validators="{this.validators}"/> |
This allows you to add an arbitrary number of validators. Then in the various inputs:
1 | <mx:TextInput id="studioNameInput" text="{this.studio.name}" width="100%" change="this.formValidator.validateForm(event);"/> |
with the button to commit the changes enabled only when the form is valid:
1 | <mx:Button id="saveChangesBtn" label="save" click="handleSaveChanges()" enabled="{this.formValidator.formIsValid}"/> |
It reduces some of the pain and tedium with the process of creating forms, which is always welcome.
Adding a ToolTip function to a ComboBox in Flex
My screens get a bit crowded sometimes, especially when dealing with forms. Users want to be able to see additional information, but there is just no place to put it. The data is dynamic though, so the toolTip needs to change based on the currently selectedItem of the ComboBox. With a DataGrid, for example, you have a showDataTip property on a column and can assign a dataTipFunction. There is no similar function in the ComboBox, but it is easy enough to add. I'm also using the HtmlToolTip class for a little extra style in the ToolTip itself.
View Source is enabled.
