Hash methods (keys, values, each) in Ruby - Step-by-Step Execution

Concept Flow - Hash methods (keys, values, each)

Start with a Hash

↓

Call keys method

→Get array of keys

↓

Call values method

→Get array of values

↓

Call each method

→Iterate each key-value pair

↓

Perform action inside block

↓

End

This flow shows how to get keys, values, and iterate over each key-value pair in a Ruby hash.

Execution Sample

Ruby

my_hash = {a: 1, b: 2, c: 3}
keys = my_hash.keys
values = my_hash.values
my_hash.each do |key, value|
  puts "#{key}: #{value}"
end

This code gets keys and values arrays from a hash and prints each key-value pair.

Execution Table

Step	Action	Evaluation	Result/Output
1	Create hash my_hash	my_hash = {a:1, b:2, c:3}	{:a=>1, :b=>2, :c=>3}
2	Call keys method	my_hash.keys	[:a, :b, :c]
3	Call values method	my_hash.values	[1, 2, 3]
4	Start each iteration, first pair	key = :a, value = 1	Prints 'a: 1'
5	Second iteration	key = :b, value = 2	Prints 'b: 2'
6	Third iteration	key = :c, value = 3	Prints 'c: 3'
7	End each iteration	No more pairs	Iteration ends

💡 All key-value pairs processed, iteration ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 7
my_hash	nil	{:a=>1, :b=>2, :c=>3}	{:a=>1, :b=>2, :c=>3}	{:a=>1, :b=>2, :c=>3}
keys	nil	[:a, :b, :c]	[:a, :b, :c]	[:a, :b, :c]
values	nil	nil	[1, 2, 3]	[1, 2, 3]
key	nil	nil	nil	nil (used inside each)
value	nil	nil	nil	nil (used inside each)

Key Moments - 3 Insights

Why does keys return an array of symbols, not a hash?

The keys method extracts only the keys from the hash and returns them as an array, as shown in step 2 of the execution_table.

What does the each method do with the key and value variables?

The each method assigns each key and value pair to the block variables key and value in each iteration, as shown in steps 4 to 6.

Does calling values change the original hash?

No, calling values returns an array of values without modifying the original hash, as seen in step 3 and variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the output of my_hash.values?

A [:a, :b, :c]

B [1, 2, 3]

C {:a=>1, :b=>2, :c=>3}

D nil

💡 Hint

Check the 'Result/Output' column at step 3 in the execution_table.

At which step does the each method print 'b: 2'?

A Step 5

B Step 6

C Step 4

D Step 7

💡 Hint

Look at the 'Action' and 'Result/Output' columns for each iteration in the execution_table.

If the hash was empty, what would keys return?

A nil

B An array with nil elements

C An empty array []

D An error

💡 Hint

Recall that keys returns an array of keys; if no keys exist, it returns an empty array.

Concept Snapshot

Hash methods in Ruby:
- keys returns an array of all keys
- values returns an array of all values
- each iterates over key-value pairs
Use each with a block: hash.each do |key, value| ... end
These methods do not modify the original hash.

Full Transcript

This visual execution shows how Ruby hash methods keys, values, and each work. First, a hash with three pairs is created. Calling keys returns an array of the keys :a, :b, and :c. Calling values returns an array of the values 1, 2, and 3. The each method loops over each key-value pair, assigning them to block variables key and value, and prints them. The iteration stops after all pairs are processed. The keys and values methods do not change the original hash. This step-by-step trace helps beginners see how these methods work and how variables change during execution.