Ruby each_with_index

Syntax

The syntax for the Ruby each_with_index method is as follows:

Here, collection refers to the object or collection you want to iterate over, such as an array or a hash. The block parameter element represents the current element being processed during each iteration, and index represents the index of that element within the collection.

Parameters

The Ruby each_with_index method takes two parameters: element and index. The element parameter represents the current element in the iteration, while the index parameter represents the index of that element within the collection.

Return Value

The return value of the Ruby each_with_index method is the original collection itself. This means that the method does not modify the collection but instead allows you to perform actions on each element while also accessing its index.

Exception

The Ruby each_with_index method does not raise any exceptions on its own. However, if an exception occurs within the block, it will propagate upwards and can be caught using standard exception-handling techniques.

How does enum#each_index differ from enum#with_each_index?

The each_index method and each_with_index method are similar in that they both provide access to the index of each element in a collection. However, there is a subtle difference between the two.

The each_index method is a shorter form of iteration that only provides the index and does not provide access to the element itself. It is useful when you only need to perform an action based on the index and do not require the element. The working of Ruby each_with_index is similar to a for loop.

On the other hand, the Ruby each_with_index method provides both the element and the index, allowing you to perform actions on each element while also having access to its index. This is especially useful when you need to manipulate or retrieve information from the elements based on their positions within the collection.

Here's an example to illustrate the difference:

As you can see, each_index only provides the index, while each_with_index allows you to access both the element and its index within the loop.

Examples

To further understand the functionality and usage of the each_with_index method, let's explore some examples:

Example 1: Iterating over an Array

Output:

In this example, we have an array of fruits. The Ruby each_with_index method is used to iterate over the array and print each fruit along with its corresponding index. The Ruby each_with_index can also be used to iterate over other data structures like sets, ranges, etc.

Example 2: Modifying Elements in Place

Output:

In this example, we have an array of numbers. The each_with_index method is used to iterate over the array and double the value of each element based on its index. The modified array is then printed using the inspect method.

Example 3: Filtering and Selecting Elements

Output:

In this example, we have an array of numbers. The each_with_index method is used to iterate over the array and check if the index is odd. The corresponding element is added to the odd_indices array if the index is odd. Finally, the odd_indices array is printed.

Example 4: Nested Iteration

One of the powerful aspects of the Ruby each_with_index method is its ability to be used in nested iterations. Let's look at an example to understand how nested iteration with each_with_index works:

Output:

Example 5: Parallel Iteration

Parallel iteration allows you to iterate over multiple collections simultaneously while accessing corresponding elements and indices. Let's consider an example to illustrate parallel iteration using each_with_index:

Output:

Example 6: Handling Enumerables with Non-numeric Indices

The each_with_index method is commonly used with collections that have numeric indices, such as arrays. However, it can also be used with enumerables that have non-numeric indices, such as hashes or sets.

Let's explore an example using a hash:

Output:

In this code snippet, we iterate over the person hash using each_with_index. Since the hash does not have numeric indices, each iteration provides a key-value pair as the first element of the block, followed by the index as the second element.

By destructuring the key-value pair into separate variables (key, value), we can access and display the key, value, and index within the block.