The invention is directed to a method which derives from metadata definitions the allowable values for a method argument, where the allowable values are a subset or a restricted set of values from a defined range of values for that type of method argument. The subset of allowable values is then converted into a fragment of source code that can be used to initialize the argument variable with one of the allowable values when the method is invoked. The fragment of source code is inserted into the source code for that method argument using an editor tool. A system for implementing the method may comprise an integrated development environment (IDE) program.