How do I build a Flex library that is compatible with client apps ranging from Flex 3.5B to Flex 4.6?

2
votes

My aim is to build a Flex library that is compatible with clients (both other libraries and Flex applications) build on Flex versions ranging from 3.5B to 4.6. Also, I'd like to be able to use functionality from as recent a version of Flex as possible in my library, although this is a secondary concern compared to compatibility.

Is it necessary that I use a Flex version no greater than 3.5B?

A particular difficulty I'm running into with 3.5B is when I statically link Flex into my library and use it in a Flex 4.5.1A project, it fails with a smörgåsbord of compile time errors like 1044: Interface method get baseline in namespace mx.core:ILayoutElement not implemented by class panels:BasePanel.

Runtime shared linking appears to somewhat address the issue. When I compile the library for Flex 3.5B with RSL of Flex set, it produces a swc that compiles cleanly in my 4.5.1A project and basically works, but I'm uncomfortable with the fact that the static option doesn't work. I feel that runtime linking in this way seems odd since a project built with Flex 3 is runtime linked with Flex 4 (any why doesn't the runtime linking produce the same interface complaints?).

Runtime linking appears so squishy (namely, I can even build my original project with 4.6 and just be super careful not to use pre-4.6 functionality and use it in a 3.5 project), that I'm uncomfortable with it with my current level of understanding.

1
actionscript-3apache-flexflex4flex3rsl

1 Answers

3
votes

Is it necessary that I use a Flex version no greater than 3.5B?

A lot of things change in Flex Framework classes between versions. So, the only way to guarantee that a SWC will work for multiple versions of the Flex SDK is to have no dependencies into the Flex SDK.

Creating a SWC library with Flex dependencies in Flex 3.5B will not necessarily work in Flex 4, or Flex 4.5 or Flex 4.6.

I've had a lot of trouble with our commercial components. Take the AutoCompleteComboBox, as one example. We currently have 5 different versions of it (Flex 3, Flex 3.2, Flex 3.5, Flex 4, and Flex 4.5 ). Each version has bug fixes specific to that version of the SDK. Flex 3.5 was a full re-write of the component because of significant changes to the Flex ComboBox, which our component extends.

Additionally, if you use a library which is compiled on a different version of the Flex SDK than your current version, sometimes the Flex compiler will give "odd" compile errors that are solved by recompiling your library with the same SDK version as your main app. I think that is exactly what you're seeing.

So, the answer is that, if you want to use a SWC with projects created for multiple versions of the Flex SDK, the only way to guarantee compatibility is to have no dependencies to the Flex SDK in your SWC.