Array creation methods in Ruby - Step-by-Step Execution

Concept Flow - Array creation methods

Start

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Choose method

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Literal: arr = [

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Array.new(size)

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Array.new(size, default_value)

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Array.new(size) { block }

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Array created

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Use array

You pick a way to create an array, Ruby builds it, then you use it.

Execution Sample

Ruby

arr1 = []
arr2 = Array.new(3)
arr3 = Array.new(3, 0)
arr4 = Array.new(3) { |i| i * 2 }

Creates arrays using different Ruby methods: empty, fixed size nils, fixed size with default, and with a block.

Execution Table

Step	Action	Code Line	Array State	Notes
1	Create empty array	arr1 = []	[]	Empty array with zero elements
2	Create array with 3 nils	arr2 = Array.new(3)	[nil, nil, nil]	Size 3, default nil
3	Create array with 3 zeros	arr3 = Array.new(3, 0)	[0, 0, 0]	Size 3, default 0 (same object)
4	Create array with block	arr4 = Array.new(3) { |i| i * 2 }	[0, 2, 4]	Size 3, values from block using index
5	End	-	-	All arrays created successfully

💡 All array creation lines executed, arrays ready for use.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
arr1	undefined	[]	[]	[]	[]	[]
arr2	undefined	undefined	[nil, nil, nil]	[nil, nil, nil]	[nil, nil, nil]	[nil, nil, nil]
arr3	undefined	undefined	undefined	[0, 0, 0]	[0, 0, 0]	[0, 0, 0]
arr4	undefined	undefined	undefined	undefined	[0, 2, 4]	[0, 2, 4]

Key Moments - 3 Insights

Why does arr3 have three zeros but they all point to the same object?

Because Array.new(3, 0) uses the same object 0 for all elements, so changing one changes all. See step 3 in execution_table.

How does the block in Array.new(3) { |i| i * 2 } work?

The block runs for each index from 0 to 2, setting each element to i*2. This creates distinct values. See step 4 in execution_table.

What is the difference between arr2 and arr3?

arr2 has three nils (default nil), arr3 has three zeros (default 0 object). arr2 elements are nil, arr3 elements are the same zero object. See steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the content of arr2?

A [nil, nil, nil]

B [0, 0, 0]

C []

D [1, 2, 3]

💡 Hint

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

At which step does the array get values from a block?

A Step 1

B Step 4

C Step 3

D Step 2

💡 Hint

Look for 'block' keyword in the 'Action' column in execution_table.

If we change arr3 to Array.new(3) { 0 }, how would the array elements differ?

A The array would be empty

B All elements would be the same object 0

C Each element would be a separate 0 object

D The array would contain nils

💡 Hint

Compare Array.new(size, obj) vs Array.new(size) { block } behavior from variable_tracker.

Concept Snapshot

Array creation methods in Ruby:
- Literal: arr = [] creates empty array
- Array.new(size) creates array with nils
- Array.new(size, obj) fills with same obj
- Array.new(size) { block } fills with block values
Use block to avoid shared objects.

Full Transcript

This visual trace shows how Ruby creates arrays using different methods. First, an empty array is made with []. Then Array.new(3) creates an array with three nil elements. Next, Array.new(3, 0) creates an array with three zeros, but all zeros are the same object. Finally, Array.new(3) with a block sets each element to a unique value based on the index. The variable tracker shows how each array changes after each step. Key moments explain why shared objects happen and how blocks create distinct elements. The quiz tests understanding of array contents and creation differences.