Programming Groovy 2

13.2 Injecting Methods Using ExpandoMetaClass

To create domain-specific languages (DSLs), we need to be able to add arbitrary methods to different classes and even hierarchies of classes. We need to inject instance methods and static methods, manipulate constructors, and convert a method to a property for the sake of fluency. We’ll want these capabilities for creating mock objects to stand in for collaborators. In this section, we’ll discuss the techniques to alter and enhance a class’s structure.

We can inject methods into a class by adding methods to its ​MetaClass​. The methods we inject are available globally. We’re not restricted to a block like in categories. We discussed ​ExpandoMetaClass​ in Section 12.2, ​Intercepting Methods Using ...