Conditional assignment (||=) in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the operator ||= do in Ruby?

It assigns a value to a variable only if that variable is currently nil or false. It means "assign if not already set."

beginner

Given name ||= "Guest", what happens if name is already "Alice"?

The value of name stays "Alice" because ||= only assigns if name is nil or false.

beginner

Why is ||= useful in Ruby programs?

It helps set default values without overwriting existing ones, making code cleaner and easier to read.

intermediate

What will be the output of this Ruby code?<br>

count = nil
count ||= 10
count ||= 20
puts count

The output will be 10. The first ||= assigns 10 because count is nil. The second ||= does nothing because count is already 10 (not nil or false).

intermediate

Can ||= assign a value if the variable is false?

Yes. ||= treats both nil and false as "not set" and will assign the new value in either case.

What does variable ||= value do in Ruby?

A Assigns value only if variable is nil or false

B Always assigns value to variable

C Assigns value only if variable is true

D Assigns value only if variable is a number

||= assigns the value only if the variable is nil or false, otherwise it keeps the original value.

If score = 0, what will score ||= 10 do?

A Assign 10 to score

B Raise an error

C Keep score as 0

D Assign nil to score

Since 0 is neither nil nor false, score ||= 10 keeps score as 0.

Which values cause ||= to assign the new value?

A Only nil

B Both nil and false

C Any value

D Only false

||= assigns the new value if the variable is either nil or false.

What is a common use of ||= in Ruby?

A To set default values

B To multiply numbers

C To delete variables

D To compare strings

||= is often used to set default values if a variable is not already set.

What will this code print?<br>

flag = false
flag ||= true
puts flag

A false

B nil

C error

D true

Since flag is false, flag ||= true assigns true to flag.

Explain how the ||= operator works in Ruby and give a simple example.

Think about setting a variable only if it doesn't have a useful value yet.

Describe a situation where using ||= can make your Ruby code cleaner.

Consider when you want to assign a value only if none exists.