AS3:使用getDefinitionByName()时，“变量[x]未定义”错误

I'm trying to use a .SWC library (exported from a .FLA document) to store graphical data for a game. In one of my classes I'm trying to attach an instance of the requested level's MovieClip, but I'm trying to use getDefinitionByName() so I can pull in the correct class based on the level number. I'm working in Flash Builder 4.7, and the SWC in question is pulled in as a build path library set to "Merged into code," in theory and up until now in practice making its classes accessible from anywhere.I'm trying to use a .SWC library (exported from