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How to Create Expander Variables

It is possible to define custom variable bindings for ExpandersExpanderA unit of generation that combines a data tree instance (functional M1 model) with a template to generate an artifact., Features etc. This can be useful to avoid having to repeat the same logic for each expanderExpanderA unit of generation that combines a data tree instance (functional M1 model) with a template to generate an artifact..

1. Implement the ExpanderVariable interface​

First, create a class that implements the ExpanderVariable interface. This class needs to implement the resolve(ExpanderVariableContext) method. It should return a VariableBinding object when it is applicable to do so.

You will also need to add the @VariableScope annotation to define where the variable is needed.

@VariableScope(ARTIFACT_PATH)
public class LayerDir implements ExpanderVariable {
  @Override
  public Optional<VariableBinding> resolve(ExpanderVariableContext context) {
    return context.getExpander()
        .map(expander -> {
          String dir = expander.getLayerType().getSubdir();
          return bind(dir).as("layerDir")
              .describedAs("Expander layer sub-directory", LayerDir.class);
        });
  }
}

2. List the variable classes​

Next, create a file META-INF/services/net.democritus.expander.variables.ExpanderVariable. In this file, list the variable classes you have implemented, each on a separate line.

net.democritus.expander.variables.locations.LayerDir

During Expansion​

The expandersExpanderA unit of generation that combines a data tree instance (functional M1 model) with a template to generate an artifact. will find the variable classes and add the variable binding to the mapping context during expansion.

<expander name="...">
  ...
  <artifactPath>$module.rootDirectory$/src/app/$layerDir$</artifactPath>
</expander>