Closures and variable binding in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a closure in Ruby?

A closure is a block, proc, or lambda that captures variables from its surrounding context, allowing it to access those variables even when executed outside that context.

intermediate

How does variable binding work inside a Ruby closure?

Variables used inside a closure capture the variables from the surrounding scope by reference, so the closure sees their updated values even if the variables change later.

intermediate

What is the difference between a Proc and a lambda in Ruby closures?

Both are closures, but lambdas check the number of arguments and return control to the calling method, while Procs are more lenient with arguments and return from the enclosing context.

advanced

Explain with an example how a closure can remember a variable's value after the variable changes.

Example: <br> x = 10<br> closure = -> { x }<br> x = 20<br> closure.call # returns 20 because closure captures variable by reference, not by value.

beginner

Why are closures useful in Ruby programming?

Closures let you write flexible code by capturing context, enabling callbacks, delayed execution, and maintaining state without global variables.

What does a Ruby closure capture from its surrounding environment?

A Only global variables

B Variables and their current values

C Only method names

D Nothing, closures have no context

Closures capture variables and their current values from the surrounding environment.

In Ruby, what happens if you change a variable after creating a closure that uses it?

A The closure breaks and raises an error

B The closure keeps the old value forever

C The closure sees the updated variable value

D The closure ignores the variable

Ruby closures capture variables by reference, so they see the updated value when called.

Which Ruby closure type checks the number of arguments strictly?

A Lambda

B Proc

C Block

D Method

Lambdas check the number of arguments strictly, unlike Procs.

What is a common use case for closures in Ruby?

A To create global variables

B To perform file I/O

C To define classes

D To delay execution and maintain state

Closures are often used to delay execution and maintain state without global variables.

Which of these is NOT a closure in Ruby?

A Class

B Proc

C Lambda

D Block

Classes are not closures; blocks, procs, and lambdas are closures.

Explain what a closure is in Ruby and how it handles variable binding.

Think about how blocks or lambdas remember variables from outside.

Describe the difference between a Proc and a lambda in Ruby closures.

Focus on argument checking and return behavior.