February 22, 2010
How to Unload Modules Effectively
It's well known that unloading modules in Flex can be tricky. The principle is simple: remove all references to the module and it will become eligible for garbage collection. The harder part is that those references can exist in unexpected places. Did you know that the code generated by the Flex 3 MXML compiler when processing a CSS stylesheet can sometimes cause a module to be pinned in memory? There are a number of causes of memory leaks like this, but they can be avoided by following certain practices.
This blog post demonstrates how to unload a Flex 3 module effectively that is styled and localized. It applies several of the techniques described in Alex Harui's earlier post, What We Know About Unloading Modules. Note that Flex 4 (out now!) and Flash Player 10.1 both bring improvements in the area of memory management, such as the modular styles sub-system in Flex 4, so not all of the points below are applicable to Flex 4 projects.
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Posted by tsugden at 9:58 PM
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February 9, 2010
The Flexible Configuration Options of Parsley
One of the nice design decisions taken by Jens Halm when he created the Parsley Application Framework was to separate the configuration mechanism from the core of the framework, so different forms of configuration can be used as required. This idea in itself is not new, since Martin Fowler advocated it in his 2004 paper, "Inversion of Control Containers and the Dependency Injection pattern":
"My advice here is to always provide a way to do all configuration easily with a programmatic interface, and then treat a separate configuration file as an optional feature. You can easily build configuration file handling to use the programmatic interface. If you are writing a component you then leave it up to your user whether to use the programmatic interface, your configuration file format, or to write their own custom configuration file format and tie it into the programmatic interface" - Martin Fowler
The application of this design principle is particularly effective in Parsley. While some frameworks are restricted to specific configuration mechanisms, Parsley provides programmatic interfaces for synchronous and asynchronous configuration, and several out-of-the-box implementations. These interfaces provide an extension-point so developers can plug-in their own configuration processors when the need arises.
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Posted by tsugden at 10:25 PM
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December 10, 2009
Writing Genuinely Reusable Flex Components
On larger projects and within enterprises, there's often a case for extracting a set of reusable components into a Flex library project. In theory, the same components can be reused across modules and sub-applications of multiple Flex or AIR clients, bringing greater consistency and more rapid development. However, in practice there are some common mistakes that limit the reusability of components. This post explains what makes a component genuinely reusable and highlights some techniques from the Flex SDK that can be applied to your own components to make them more reusable.
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Posted by tsugden at 9:18 AM
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November 23, 2009
Modularity in Flex Applications
There has been talk recently about the trend towards inversion-of-control frameworks in Flex. In addition to this, a higher-level movement can be seen towards modularity frameworks. Such an approach to architecture can bring many benefits, particularly in enterprise settings with larger teams and formal release processes. This post explains what modularity means in the context of Flex and discusses some of the benefits and options available for implementation.
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Posted by tsugden at 10:32 PM
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September 29, 2009
Vote for Morgan Stanley Matrix!
Morgan Stanley Matrix has reached the finals for a MAX Award in the Enterprise Productivity category. You can view the vignettes and cast your vote at:
Public voting has started and the voting will be live until Tuesday, October 6, when the winners will be announced at the event. For more info about Morgan Stanley Matrix, see my earlier blog post or come to the Building Morgan Stanley Matrix session at MAX next week.
Posted by tsugden at 1:59 PM
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September 21, 2009
Morgan Stanley Matrix at MAX
Next month at Adobe MAX 2009 in Los Angeles, Børre Wessel (Lab49) and myself will be presenting Matrix, the next-generation sales and trading platform from Morgan Stanley.
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Posted by tsugden at 9:40 PM
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September 13, 2009
Coming Soon: Cairngorm 3
Cairngorm is about to undergo a transformation that will broaden its scope and increase its value to clients and partners. Instead of centering around a specific implementation of the Model-View-Controller pattern, Cairngorm 3 will consist of a set of best practices, tools and libraries, many of which apply across frameworks. This is the knowledge gathered by the Adobe Technical Services organization and partners over the last five or six years, condensed and presented to help others to deliver successful Flex projects in the enterprise.
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Posted by tsugden at 8:57 PM
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September 4, 2009
Eliminate Common Bad Practices with FlexPMD
Adobe Technical Services are pleased to release FlexPMD to the community. FlexPMD is a new open-source tool for improving code quality. It works by analyzing ActionScript and MXML source files to identify common bad practices, like over-long classes or functions, reliance on magic strings, unused parameters, and many other programming mistakes or misjudgments. It can even spot code that might be causing performance problems, and furthermore, the ruleset can be customized and extended, to include rules specific to the coding conventions of your own project.
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Posted by tsugden at 7:21 AM
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August 24, 2009
Applying the Presentation Model in Flex
The purpose of the Presentation Model design pattern is simple to grasp: it’s a way of moving state and logic out of a view component and into another class, where it can be developed, comprehended and unit tested more easily. The pattern promotes a clean separation of concerns, helping to keep MXML views as structural definitions, free from Script-block logic. However, there are several ways to apply presentation models in Flex. Some of these can help us to build simpler, more testable systems, while others may lead towards entanglement and maintenance difficulties.
For a comprehensive introduction to the Presentation Model pattern and a comparison between it and other presentation patterns, please refer to Paul Williams' blog series on the topic. At Adobe Professional Services, we have found the Presentation Model to be well suited to Flex, since it takes advantage of language features like bindings and in-line event handlers, while side-stepping some of the difficulties of unit testing display objects.
This article discusses two approaches to applying the Presentation Model -- hierarchical and componentized -- and makes a recommendation in favour of the latter.
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Posted by tsugden at 9:32 PM
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August 11, 2009
Best Practices for the Flex Logging Framework
The Flex Logging Framework is easy to learn and flexible to use. It supports many different scenarios, from helping developers to debug their code, to sending the details of production application errors over the wire to a remote server for monitoring. To learn the basics of the Logging Framework refer to the latest Flex Developer Guide and the Flex Logging Framework chapter of Professional Flex 3. This document describes some best practices for applying the Logging Framework on enterprise projects.
The APIs provided by the Logging Framework are simple, but they need to be used properly to get the best out of them. If care is not taken, the benefits that logging can provide for debugging and monitoring an application in production can be lost. Performance problems can even be created. This article provides a set of best practices to keep the developers in your team on the right track.
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Posted by tsugden at 9:15 AM
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