What Causes Flash Error #2012 (Can’t instantiate class)

actionscript-3apache-flexflashflexbuilder

I am new to ActionScript 3 and have run into a problem:

Using Flex Builder 3, I have a created a project with a few simple classes. If code in class A instantiates an object of class B (class B is in its own source file) then the code compiles fine, but I get the following run time error:

ArgumentError: Error #2012: B class cannot be instantiated.

Can someone explain what I'm doing wrong?

Update: Please see my own answer below (I could not vote it to the top since I'm not yet registered).

Best Answer

I finally realized what was wrong: Class B was subclassing from DisplayObject which I now see is an abstract class. Class B did not implement the abstract members, thus the error. I'll probably change class B to subclass from Sprite instead.

This seems like a problem that should have been caught by the compiler. Does the fact that it wasn't mean implementation of abstract members can wait until run time? Even if so, it would be nice to at least get a compiler warning.

Thanks for everyone's answers, hopefully they will help others who run into error 2012.

Related Solutions

R – differences when compiling a project using flex builder and flex sdk

The paths have to be explicitly defined using mxmlc or compc. Here is an explanation of the flags:

source-path is used to define the path to the source if it is not in the default:

mxmlc -source-path path1 path2 path3 c:/myFiles/app.mxml

library-path is used to define the path to libraries:

mxmlc -library-path [AIR SDK]/frameworks/libs/air/airframework.swc, ^ [AIR SDK]/frameworks/libs/air/airframework.swc, ^ -library-path [Flex SDK]/frameworks/libs/framework.swc ^ -- myApp.mxml

file-specs is used to define the mxml file:

mxmlc --strict=true --file-specs MyFirst.mxml

runtime-shared-libraries is used to define the RSL path:

mxmlc -external-library-path+=../lib/myLib.swc -runtime-shared-libraries=myrsl.swf -- myApp.mxml

References

Git + Flash Builder workflow: how to set it up so git works smoothly

I've found a good solution which avoids all of the horror of having untracked files and keeping a massive .ignore list:

CLEAN your projects before you git commit.

Simple as that.

Whether it be by Flash Builder or by ant, you should have the ability to clean anyway, so if you simply clean before you commit, the problem of generated files is solved. Duh.

In fact you could probably set it up as a git hook or something.

Best Answer

Related Solutions

R – differences when compiling a project using flex builder and flex sdk

Git + Flash Builder workflow: how to set it up so git works smoothly

Related Topic