Map/collect for transformation in Ruby - Step-by-Step Execution

Concept Flow - Map/collect for transformation

Start with an array

↓

Apply map/collect block

↓

Transform each element

↓

Collect transformed elements

↓

Return new array with transformed values

This flow shows how map/collect takes each element from an array, transforms it, and returns a new array with the transformed elements.

Execution Sample

Ruby

numbers = [1, 2, 3]
squares = numbers.map { |n| n * n }
puts squares.inspect

This code squares each number in the array and prints the new array.

Execution Table

Step	Current Element (n)	Block Operation	Result for Element	New Array State
1	1	1 * 1	1	[1]
2	2	2 * 2	4	[1, 4]
3	3	3 * 3	9	[1, 4, 9]
4	-	End of array	-	[1, 4, 9]

💡 All elements processed, map returns new array with squared values.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
numbers	[1, 2, 3]	[1, 2, 3]	[1, 2, 3]	[1, 2, 3]	[1, 2, 3]
n	-	1	2	3	-
squares	[]	[1]	[1, 4]	[1, 4, 9]	[1, 4, 9]

Key Moments - 2 Insights

Why does the original array 'numbers' not change after using map?

Because map returns a new array with transformed values and does not modify the original array, as shown in the variable_tracker where 'numbers' stays the same.

What happens if the block inside map does not return a value?

If the block returns nil or nothing, the new array will have nil for that element. Each block's return value becomes the new element, as seen in the execution_table's 'Result for Element' column.

Visual Quiz - 3 Questions

Look at the execution_table, what is the new array state after processing the second element?

A [1, 2]

B [4]

C [1, 4]

D [1, 4, 9]

💡 Hint

Check the 'New Array State' column at step 2 in the execution_table.

At which step does the variable 'n' have the value 3?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Current Element (n)' column in the execution_table.

If the block was changed to 'n + 1', what would be the final 'squares' array in variable_tracker?

A [1, 2, 3]

B [2, 3, 4]

C [1, 4, 9]

D [0, 1, 2]

💡 Hint

Think about adding 1 to each element in the original array [1, 2, 3].

Concept Snapshot

map/collect syntax: array.map { |element| transformation }
Returns a new array with each element transformed.
Original array stays unchanged.
Block return value becomes new element.
Useful for changing data without side effects.

Full Transcript

This visual execution shows how Ruby's map or collect method works. Starting with an array of numbers, each element is taken one by one. The block multiplies each element by itself, creating a square. Each result is added to a new array. The original array remains unchanged. The final output is a new array of squared numbers. This helps transform data cleanly and simply.