Compact for removing nil values in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the compact method do in Ruby?

It returns a new array with all nil values removed from the original array.

beginner

How do you use compact on an array [1, nil, 2, nil, 3]?

You call [1, nil, 2, nil, 3].compact, which returns [1, 2, 3].

intermediate

What is the difference between compact and compact!?

compact returns a new array without nil values, while compact! modifies the original array in place and returns nil if no changes were made.

beginner

Can compact remove values other than nil?

No, compact only removes nil values. Other falsy values like false remain in the array.

beginner

Why might you want to use compact in your Ruby code?

To clean up arrays by removing unwanted nil values, which can help avoid errors or simplify processing.

What does [1, nil, 3].compact return?

A [3]

B [nil]

C [1, nil, 3]

D [1, 3]

The compact method removes all nil values, so the result is [1, 3].

What does compact! do differently than compact?

A Modifies the original array in place

B Returns a new array without nils

C Removes false values

D Does nothing

compact! changes the original array by removing nil values directly.

If an array has no nil values, what does compact! return?

A The original array

B A new array

C nil

D An error

compact! returns nil if no changes were made to the array.

Which values does compact remove?

A All falsy values

B Only nil values

C Only false values

D nil and false values

compact removes only nil values, not false.

How can compact help in Ruby programming?

A By cleaning arrays from nils to avoid errors

B By sorting arrays

C By converting arrays to strings

D By adding nil values

compact helps clean arrays by removing nil values, making code safer and simpler.

Explain how the compact method works in Ruby and when you might use it.

Think about cleaning up arrays by removing empty spots.

Describe the difference between compact and compact! in Ruby.

One changes the original array, the other does not.