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

Defining database schemas at runtime

Answer

Compiling Groovy scripts to native bytecode

Answer

Managing dependency injection containers

Question 2

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

Accepted Answer

GroovyInterceptable

Answer

GroovyCallable

Answer

DynamicObject

Answer

MetaMethod

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

It permanently modifies the JVM bytecode of the target class

Answer

It creates a subclass with the additional method

Answer

It generates a Groovy AST transformation

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

To define abstract methods that must be overridden in subclasses

Answer

To mark deprecated methods that should be avoided

Answer

To declare optional interface methods with default implementations

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

Categories

Answer

Traits

Answer

Mixins

Answer

Delegates

Question 6

What does the `@Delegate` AST transformation in Groovy do?

Accepted Answer

Generates delegation methods so the annotated field's methods become part of the enclosing class's API

Answer

Marks a method to be called asynchronously

Answer

Declares the class as a singleton managed by Grails

Answer

Enables compile-time null-safety checks on the annotated field

Question 7

In Groovy, what is a Trait primarily used for?

Accepted Answer

Providing reusable method implementations that can be mixed into multiple classes

Answer

Defining immutable value objects

Answer

Annotating classes for Spring component scanning

Answer

Specifying database table mappings for GORM