Hash methods (keys, values, each) in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the keys method do in a Ruby hash?

It returns an array containing all the keys from the hash.

beginner

What does the values method return when called on a Ruby hash?

It returns an array of all the values stored in the hash.

beginner

How does the each method work on a Ruby hash?

It goes through each key-value pair in the hash and lets you run code for each pair.

beginner

Given h = {a: 1, b: 2}, what is the output of h.keys?

[:a, :b]

intermediate

Explain the difference between each and each_key methods in Ruby hashes.

each iterates over key-value pairs, while each_key iterates only over keys.

What does hash.values return?

A The first key-value pair

B An array of all keys in the hash

C The number of key-value pairs

D An array of all values in the hash

values returns all the values stored in the hash as an array.

Which method lets you run code for each key-value pair in a Ruby hash?

A keys

B each

C values

D length

each iterates over each key-value pair allowing you to run code on them.

What is the output of {x: 10, y: 20}.keys?

A [:x, :y]

B [10, 20]

C [:10, :20]

D An error

keys returns an array of the keys, which are :x and :y.

If you want only the keys from a hash, which method do you use?

A keys

B select

C each

D values

The keys method returns only the keys from the hash.

What does the each method yield to the block when called on a hash?

A Only the key

B Only the value

C Both key and value as two block parameters

D An array of keys

each yields both key and value to the block, usually as two parameters.

Describe how you would use the each method to print all keys and values of a hash.

Think about how a hash stores pairs and how each lets you access them.

Explain the difference between keys and values methods in Ruby hashes.

Focus on what part of the hash each method extracts.