Groovy and Grails Groovy Language Fundamentals & Metaprogramming 2

Question 1

What is Groovy's Meta-Object Protocol (MOP) primarily used for?

Accepted Answer

Intercepting and modifying method calls and property access dynamically

Answer

The MOP allows Groovy programs to intercept, synthesize, and delegate method calls and property access at runtime.

Question 2

Which Groovy interface must a class implement to intercept calls to methods that do not exist on it?

Accepted Answer

GroovyInterceptable

Answer

Implementing `GroovyInterceptable` causes all method calls on an object to go through `invokeMethod`, even existing ones.

Question 3

In Groovy metaprogramming, what does adding a method to `ExpandoMetaClass` achieve?

Accepted Answer

It adds the method to all instances of that class at runtime without modifying source code

Answer

`ExpandoMetaClass` lets you add methods to existing classes at runtime, visible to all instances, without touching source code.

Question 4

What is the purpose of the `methodMissing` hook in Groovy?

Accepted Answer

To catch calls to methods that don't exist and handle them dynamically

Answer

`methodMissing` is invoked when a called method is not found, enabling dynamic method generation or delegation.

Question 5

Which Groovy feature allows you to add methods to an existing class temporarily within a defined scope using a helper class?

Accepted Answer

Groovy and Grails Practice Test