Each as the primary iterator in Ruby - Step-by-Step Execution

Concept Flow - Each as the primary iterator

Start with collection

↓

Call each method

↓

Take first element

↓

Execute block with element

↓

Move to next element

↓

More elements?

No→End iteration

↩Back to Execute block

The each method takes one element at a time from a collection and runs the given block on it until all elements are processed.

Execution Sample

Ruby

numbers = [1, 2, 3]
numbers.each do |num|
  puts num * 2
end

This code goes through each number in the list and prints double its value.

Execution Table

Step	Current Element (num)	Block Execution	Output	Next Action
1	1	puts 1 * 2	2	Move to next element
2	2	puts 2 * 2	4	Move to next element
3	3	puts 3 * 2	6	No more elements, end iteration

💡 All elements processed, each iteration ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
num	nil	1	2	3	nil

Key Moments - 3 Insights

Why does the variable 'num' change each time in the block?

Because 'each' takes one element at a time from the collection and assigns it to 'num' before running the block, as shown in steps 1 to 3 in the execution_table.

What happens after the last element is processed?

The iteration stops because there are no more elements to assign to 'num', as explained in the exit_note and step 3 of the execution_table.

Does 'each' change the original collection?

No, 'each' only reads elements one by one and runs the block; it does not modify the original collection.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'num' at step 2?

A 1

B 3

C 2

D nil

💡 Hint

Check the 'Current Element (num)' column at step 2 in the execution_table.

At which step does the iteration end according to the execution_table?

A Step 1

B After Step 3

C Step 3

D Step 2

💡 Hint

Look at the 'Next Action' column and the exit_note for when iteration stops.

If the array had one more element, how would the execution_table change?

A There would be an extra step with that element as 'num'.

B The iteration would stop earlier.

C The output would be empty.

D The variable 'num' would not change.

💡 Hint

Refer to how each element is processed step-by-step in the execution_table.

Concept Snapshot

each method syntax:
collection.each do |element|
  # code using element
end

Behavior:
- Takes one element at a time
- Runs block with that element
- Continues until all elements done
- Does not modify original collection

Full Transcript

The 'each' method in Ruby goes through every item in a collection one by one. For each item, it assigns it to a variable (like 'num') and runs the code inside the block. This continues until all items are processed. The original collection stays the same. In the example, numbers 1, 2, and 3 are doubled and printed. The variable 'num' changes each step to the current element. When no elements remain, the iteration ends.