How to Merge Two Arrays in Ruby: Simple Syntax and Examples

In Ruby, you can merge two arrays using the + operator or the concat method. The + operator returns a new array combining both arrays, while concat modifies the original array by adding elements from the second array.

Syntax

There are two common ways to merge arrays in Ruby:

• array1 + array2: Returns a new array with elements from both arrays.
• array1.concat(array2): Adds elements of array2 to array1 modifying it.

ruby

merged_array = array1 + array2
array1.concat(array2)

Example

This example shows how to merge two arrays using both the + operator and the concat method.

ruby

array1 = [1, 2, 3]
array2 = [4, 5, 6]

# Using + operator
merged = array1 + array2
puts "Merged with +: #{merged.inspect}"

# Using concat method
array1.concat(array2)
puts "Array1 after concat: #{array1.inspect}"

Output

Merged with +: [1, 2, 3, 4, 5, 6]
Array1 after concat: [1, 2, 3, 4, 5, 6]

Common Pitfalls

A common mistake is expecting + to modify the original array. It does not; it returns a new array instead. Also, using concat changes the original array, which might be unexpected if you want to keep it unchanged.

ruby

array1 = [1, 2]
array2 = [3, 4]

# Wrong: expecting array1 to change
array1 + array2
puts array1.inspect  # Output: [1, 2]

# Right: use concat to modify array1
array1.concat(array2)
puts array1.inspect  # Output: [1, 2, 3, 4]

Output

[1, 2]
[1, 2, 3, 4]

Quick Reference

Summary of methods to merge arrays in Ruby:

Method	Description	Modifies Original?
array1 + array2	Returns a new merged array	No
array1.concat(array2)	Adds elements of array2 to array1	Yes
array1.push(*array2)	Adds elements of array2 to array1	Yes

Key Takeaways

Use + to merge arrays without changing originals.

Use concat to add elements to an existing array.

Remember + returns a new array; it does not modify.

Be careful with concat as it changes the original array.

You can also use push(*array2) to merge arrays in place.