Table of contents
Revisited on May 25th, 2023
Hey guys, how's it going?
Introduction
Today, let's learn about 5 effective ways to add items to arrays in Ruby. As always, you don't need to memorize them all, however I think it's always a good idea to know that you have a wide variety of options.
Introduction to Arrays
First things first, what are Arrays?
Arrays are ordered, integer-indexed collections of any object.
So, it's important to remember that array items:
can be any object;
have a specific order;
are indexed by integer values;
Got that? So, each element of an array is associated with an integer value. Just like in a lot of other programming languages, such as C and Java, the first index value starts with 0. It might sound funny, but it's possible to have negative index values, they start with -1. The index value -1 refers to the last element of the array, -2 is the second last element of the array and so on.
Example of an array
irb(main):007:0> array = [1, 'chocolate', '2', 0]
irb(main):008:0> array
=> [1, "chocolate", "2", 0]
5 effective ways to add items to Arrays in Ruby
The order of the items is an important characteristic of arrays in Ruby, so, it's necessary to choose where is the new item going to be.
The most common position is at the end of the array, however it's possible to insert before all other array items or at any position. To sum up, you can choose any position.
First approach - Using the push method
In the following example, the item 10 is added to the end of the array.
irb(main):001:0> array = [1, 'chocolate', '2', 0]
=> [1, "chocolate", "2", 0]
irb(main):003:0> array.push(10)
=> [1, "chocolate", "2", 0, 10]
In this example, the item "new item" is added to the end of the array.
irb(main):004:0> array
=> [1, "chocolate", "2", 0, 10]
irb(main):005:0> array.push("new item")
=> [1, "chocolate", "2", 0, 10, "new item"]
The push method also allows to insert multiple values all at once. Check it out.
irb(main):001:0> array = [1, "chocolate", "2", 0, 10, "new item"]
irb(main):002:0> array.push(2, 3)
=> [1, "chocolate", "2", 0, 10, "new item", 2, 3]
irb(main):003:0> array.push("new", "value", 10)
=> [1, "chocolate", "2", 0, 10, "new item", 2, 3, "new", "value", 10]
irb(main):004:0>
The push method returns the array itself.
irb(main):007:0> array = [1, "chocolate", "2", 0, 10, "new item", 2, 3, "new", "
value", 10]
irb(main):008:0> array.push("99")
=> [1, "chocolate", "2", 0, 10, "new item", 2, 3, "new", "value", 10, "99"]
irb(main):009:0>
Second approach - Using the << method
The << method also insert values at the end of the array. In String type objects, the << method appends a substring to a string.
irb(main):012:0> array = [2, 1, 4, 3]
irb(main):013:0> array << 0
=> [2, 1, 4, 3, 0]
It's possible to add multiple values, however not all at once. If it's necessary to insert more than one value, then the << method needs to be used as many times as the number of items.
irb(main):014:0> array = [2, 1, 4, 3]
irb(main):015:0> array << 0 << 1 << 2
=> [2, 1, 4, 3, 0, 1, 2]
In the previous example, the << method was three times, because three values were inserted at the end of the array.
The << method returns the array itself.
irb(main):003:0> array = [2, 1, 4, 3]
irb(main):004:0> array << 9
=> [2, 1, 4, 3, 9]
The third approach - Using the unshift method
The unshift method adds items to the beginning of the array.
irb(main):005:0> array = [2, 1, 4, 3]
irb(main):006:0> array.unshift(0)
=> [0, 2, 1, 4, 3]
The unshift method allows you to add multiple items at the same time.
irb(main):008:0> array = [2, 1, 4, 3]
irb(main):009:0> array.unshift(0, 1)
=> [0, 1, 2, 1, 4, 3]
It returns the array itself.
irb(main):008:0> array = [2, 1, 4, 3]
irb(main):009:0> array.unshift(0, 1)
=> [0, 1, 2, 1, 4, 3]
The fourth approach - Using the insert method
Syntax
array.insert(index number, array item)
The insert method allows to insert an item at any position. It can also be used to add a substring to a string.
irb(main):008:0> array = [2, 1, 4, 3]
irb(main):009:0> array.insert(2, 0)
=> [2, 1, 0, 4, 3]
If only one argument is passed, the method does nothing, it only returns the array itself.
irb(main):007:0> array = [2, 1, 4, 3]
irb(main):008:0> array.insert(4)
=> [2, 1, 4, 3]
Negative index number are allowed, the index value -1 refers to the last element of the array, -2 is the second last element of the array and so on.
irb(main):009:0> array = [2, 1, 4, 3]
irb(main):010:0> array.insert(-1, 0)
=> [2, 1, 4, 3, 0]
It's possible to add multiple values all at once. The first argument is the index number, the other ones are the values.
irb(main):011:0> array = [2, 1, 4, 3]
irb(main):012:0> array.insert(2, 1, 2)
=> [2, 1, 1, 2, 4, 3]
The insert method returns the array itself.
irb(main):008:0> array = [2, 1, 4, 3]
irb(main):009:0> array.insert(2, 0)
=> [2, 1, 0, 4, 3]
The fifth approach - Using the direct index
In this approach, the value is assigned to the chosen index value. No method is used here.
Syntax
array[index] = object value
In the following example, the value 5 is assigned to the index 4.
irb(main):004:0> array = [1, 4, 3, 2]
irb(main):005:0> array[4] = 5
irb(main):006:0> array
=> [1, 4, 3, 2, 5]
Using this approach, there's no return.
irb(main):004:0> array = [1, 4, 3, 2]
irb(main):005:0> array[4] = 5
If an index is skipped, nil values are assigned until the specific matching index. Consider an array with 4 elements, the index starts with 0 and ends with 3. If the value 0 is assigned to the index 6, then index 4 and 5 are going to have nil values.
irb(main):001:0> array = [1, 4, 3, 2]
irb(main):002:0> array[6] = 0
irb(main):003:0> array
=> [1, 4, 3, 2, nil, nil, 0]
Conclusion
In this article, it was possible to learn 5 effective ways to add items to Arrays in Ruby. I hope this article has been useful in your development life. Thanks for dropping by.
Hope to see you soon!