Demystifying Enumerable Methods in Ruby: Map, Collect, Select, Each, and More

Ashvin Choudhary
3 min readJun 5, 2023

Ruby, a dynamic and expressive programming language, provides a wealth of powerful methods for manipulating arrays and collections. Among these methods are `map`, `collect`, `select`, and `each`, which are frequently used to transform, filter, and iterate over data. In this blog post, we will explore these methods in detail, understand their differences, and introduce a few other essential enumerable methods that you might find useful.

1. The `map` Method:
The `map` method allows you to transform each element of an array according to a given block of code. It creates a new array containing the results of applying the block to each element. Here’s an example:

numbers = [1, 2, 3, 4]
squared_numbers = numbers.map { |num| num ** 2 }
# squared_numbers => [1, 4, 9, 16]

In this example, the `map` method applies the block `{ |num| num ** 2 }` to each element in the `numbers` array, resulting in a new array `squared_numbers` with the squared values.

2. The `collect` Method:
The `collect` method is synonymous with `map`. It behaves exactly the same way, allowing you to transform each element of an array using a block. The two methods can be used interchangeably, and their effects are identical.

3. The `select` Method:
The `select` method is used for filtering elements based on a given condition. It creates a new array that includes only the elements for which the condition evaluates to `true`. Here’s an example:

numbers = [1, 2, 3, 4]
even_numbers = numbers.select { |num| num.even? }
# even_numbers => [2, 4]

In this example, the `select` method filters the `numbers` array and returns a new array `even_numbers` that contains only the even numbers.

4. The `each` Method:
The `each` method is used to iterate over an array or collection and perform an action on each element without modifying the original array. Unlike `map`, `collect`, and `select`, it doesn’t create a new array. Instead, it allows you to perform custom operations on each element. Here’s an example:

fruits = [‘apple’, ‘banana’, ‘orange’]
fruits.each { |fruit| puts “I love #{fruit}s!” }
# Output:
# I love apples!
# I love bananas!
# I love oranges!

In this example, the `each` method iterates over the `fruits` array and executes the block of code for each element, printing a personalized message.

Other Useful Enumerable Methods:

5. The `find` Method:
The `find` method is used to locate and return the first element in an array that satisfies a given condition. It stops iterating once the condition is met. If no element satisfies the condition, it returns `nil`. Here’s an example:

numbers = [1, 2, 3, 4]
found_number = numbers.find { |num| num > 2 }
# found_number => 3

In this example, the `find` method searches for the first number greater than 2 and returns it.

6. The `reduce` Method:
The `reduce` method, also known as `inject`, allows you to accumulate a single value by applying a binary operation to each element of an array successively. Here’s an example:

numbers = [1, 2,3, 4]
sum = numbers.reduce(0) { |total, num| total + num }
# sum => 10

In this example, the `reduce` method adds each element of the `numbers` array to the `total`, starting with an initial value of 0, resulting in the sum of all elements.

Conclusion:
Understanding the differences between `map`, `collect`, `select`, and `each` is crucial for effectively manipulating and transforming data in Ruby. Additionally, exploring other essential enumerable methods like `find` and `reduce` expands your toolkit for working with arrays and collections. By harnessing the power of these methods, you can write concise and elegant code, making your Ruby programming experience even more enjoyable and efficient.

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Ashvin Choudhary

Ashvin Choudhary is an AWS Certified Senior Software Engineer with 8+ years of experience. He's enthusiastic about tech and believes in lifelong learning.