The Ultimate Guide to Porting Flash 7 AS2 Projects to Flex AS3

In the world of technology, change is inevitable. If you’re one of the many developers looking to update your preexisting projects from Flash 7/AS2 to Flex/AS3, you might find the transition more challenging than anticipated. The differences between ActionScript 2 (AS2) and ActionScript 3 (AS3) can create significant hurdles, especially when dealing with larger codebases. This blog post will walk you through the best approaches to make this migration smooth and successful.

Understanding the Differences: AS2 vs. AS3

Before diving into how to port your project, let’s take a moment to understand what has changed between AS2 and AS3. While the general syntax may seem similar, there are several key differences that need to be addressed:

• Class Structure: In AS2, classes could be defined directly without a package, while AS3 mandates a package declaration.
• Import Statements: AS3 requires explicit import statements for any external classes, as referring to classes by their fully qualified name is no longer sufficient.
• Keywords and Modifiers: Certain keywords are used differently, requiring additional clarity in your code.

Key Challenges in Porting AS2 to AS3

When porting a significant amount of code from AS2 to AS3, you’ll likely encounter several notable challenges. Here are some of the primary issues to be aware of:

1. Package Naming Changes

• AS2 Example:

  class your.package.YourClass {
  }
  

• AS3 Conversion:

  package your.package {
      class YourClass {
      }
  }
  

• Ensure that every class is correctly encapsulated within its respective package.

2. Explicit Imports Required

• AS3 mandates explicit import statements. This means every class that will be utilized from outside must be imported properly, as the shorthand method from AS2 will not work.

3. No ‘Public’ on Interface Methods

• In AS3, you cannot label interface methods as public. This shift might lead to refactoring in your code to comply with AS3 conventions.

4. Override Keyword Usage

• Functions that override parent class functions must be declared with the override keyword in AS3. This change also applies to interfaces that extend one another, where unnecessary overrides will have to be eliminated.

5. Changes to Built-in Flash Classes

• The built-in classes have also undergone changes. For instance, MovieClip should now be referenced as flash.display.MovieClip. Familiarize yourself with these adjustments to avoid confusion.

Automating the Porting Process

While dealing with the manual changes can be tedious, consider automating parts of the process. For example, creating a simple tool to automate refactoring can save you significant time. Developers have successfully crafted tools using languages such as C# that address most of these porting issues—except for the override keyword complexities.

• Run a Refactoring Tool: A script can often automate:
  • Package restructuring
  • Import statement inserts
  • Keyword adjustments

Conclusion

Transitioning from Flash 7 and AS2 to Flex and AS3 can be a complex task filled with challenges but is entirely feasible with the right approach. Familiarizing yourself with the critical differences, tackling common pitfalls, and embracing automation can help pave the way for future development in Flex.

In closing, stay updated, be patient, and don’t hesitate to seek help from the community as you navigate this transition. Happy coding!