Arrays are a common data structure to work with.
Thereby, there is a collection of methods that can be used to deal with arrays.
Which includes sorting, reversing, inserting, and many more.
Some of these methods are destructive, which means that they modify the original array.
Others are non-destructive, meaning they return a new array and do not modify the original one.
Here are a few of the most common methods that can be used when dealing with arrays:
insert
When inserting an element in an array, you can use the insert method, which takes an index and an element as arguments.
The element will be inserted at the specified index, and the rest of the array will be shifted to the right.
If the index is out of bounds, then an IndexError will be raised.
numbers = [1, 2, 3]
numbers.insert(1, 4)
numbers # => [1, 4, 2, 3]
numbers.insert(5, 5) # => Error: Index out of bounds (IndexError)
delete
When you want to delete a specific element from an array, you can use the delete method, which takes an element as an argument.
The method returns the element that was removed.
If the element does not exist in the array, then nil will be returned.
numbers = [1, 2, 3]
numbers.delete(2) # => 2
numbers # => [1, 3]
first & last
When wanting to get the first or last element of an array, you can use the first and last methods.
These methods take an optional argument specifying how many elements to return.
These can improve readability compared to using the index 0 or -1, or using a range.
If the array is empty, an Enumerable::EmptyError will be raised.
numbers = [1, 2, 3]
numbers.first # => 1
numbers.last # => 3
numbers.first(2) # => [1, 2]
numbers.last(2) # => [2, 3]
empty_array = [] of Int32
empty_array.last # => Error: Empty enumerable (Enumerable::EmptyError)
reverse
When wanting to reverse an array, you can use the reverse method which returns a new array with the elements in reverse order.
It is important to note that reverse returns a new array and does not modify the original array.
If you want to modify the original array, add a ! to the end of the method name.
numbers = [1, 2, 3]
numbers.reverse # => [3, 2, 1]
numbers # => [1, 2, 3]
numbers.reverse! # => [3, 2, 1]
numbers # => [3, 2, 1]
Concat(+)
The append method(<<) is useful when wanting to add objects to an array.
However, when combining two arrays, you can use the + operator, which returns a new array with the elements of both arrays.
[1, 2] + [3, 4] # => [1, 2, 3, 4]
If you append an array to another array, the array will be added as a single element.
[1, 2] << [3, 4] # => [1, 2, [3, 4]]
empty?
When checking if an array is empty, you can use the empty? method, which returns true if the array is empty and false otherwise.
This improves readability compared to checking the array's length against 0.
[].empty? # => true
[1, 2, 3].empty? # => false
index
When you want to get the index of an element in an array, you can use the index method, which takes an element as an argument.
If the element does not exist in the array, then nil will be returned.
numbers = [1, 2, 3]
numbers.index(2) # => 1
size
When you want to know the number of elements in an array, you can use the size method.
numbers = [1, 2, 3]
numbers.size # => 3
count
When you want to count the number of times an element is present in an array, you can use the count method.
fruits = ["apple", "banana", "apple"]
fruits.count("apple") # => 2
fruits.count("banana") # => 1
fruits.count("watermelon") # => 0
sort
When you want to sort an array, you can use the sort method, which returns a new array with the elements sorted.
As with reverse, this method returns a new array and does not modify the original array.
numbers = [3, 2, 1]
numbers.sort # => [1, 2, 3]
numbers # => [3, 2, 1]
numbers.sort! # => [1, 2, 3]
numbers # => [1, 2, 3]
Learning Exercise
