Ruby Strings

A string is a data type used to represent textual data.

message = "Hello, world!"
puts message

# Output: Hello, world!

Create a String

In Ruby, you can create a string by wrapping text in double quotes (") or single quotes ('). For example,

greeting = "Good Morning"
language = 'Ruby'

Here, "Good Morning" and 'Ruby' are strings.

String Interpolation

String interpolation lets you insert the value of a variable inside a string. For example,

name = "Taylor"
puts "Hello #{name}"

Output

Hello Taylor

Inside the string, #{name} tells Ruby to look at the name variable and insert its value right there.

However, string interpolation works only inside double-quoted strings. It won't work inside single-quoted strings. For example,

name = "Taylor"
puts 'Hello #{name}'

Output

Hello #{name}

puts "2 + 2 is #{2 + 2}"

2 + 2 is 4

String Concatenation

String concatenation means joining strings together to form a single string.

In Ruby, there are a few ways to perform string concatenation.

1. Using the + operator

You can join two strings with the + sign:

first_name = "Amber"
last_name = "Smith"

# Concatenates the first and last name with a space in between
puts first_name + " " + last_name

Output

Amber Smith

In the above example, we joined "Amber", a space " ", and "Smith" into one full string using the + operator.

2. Using the << operator

You can use the << operator to add one string to the end of another. For example,

greeting = "Hello"
greeting << ", world!"
puts greeting

Output

Hello, world!

Accessing Characters in a String

Ruby strings are made up of characters, and each character has a position (called an index), starting from 0.

You can access individual characters in a string using square brackets [].

text = "hello"
puts text[0]   
puts text[1]   

Output

h
e

In this example:

• text[0] gives you the first character: "h".
• text[1] gives you the second character: "e".

Ruby String Methods

In Ruby, strings are objects — and that means you can call methods on them to perform operations like changing case, checking length, or replacing characters.

Let's see some of the common string operations using methods.

1. Change the Case of a String

To change the case of a string, you can use the .upcase and .downcase methods.

puts "hello".upcase    
puts "WORLD".downcase 

# Output: 
# HELLO
# world

Here,

• upcase converts all letters to uppercase: "hello" to "HELLO".
• downcase converts all letters to lowercase: "WORLD" to "world".

2. Get the Length of a String

To find out how many characters are in a string, use the .length method.

puts "Ruby".length 

# Output: 4

3. Remove Extra Spaces

To remove spaces from the beginning and end of a string, use the .strip method.

puts "  hello  ".strip  

# Output: hello

4. Replace Part of a String

To replace parts of a string with something else, use the .gsub method.

puts "dog".gsub("d", "f")
puts "I like cats and cats like me".gsub("cats", "dogs")  

# Output:
# fog
# I like dogs and dogs like me

The gsub method replaces all occurrences of the matched string or pattern in the given string. For example, both instances of "cats" are replaced with "dogs".

5. Check if a String Contains Something

To check whether a certain word or letter exists in a string, use the .include? method.

The .include? the method returns true if the given substring is found inside the string, else it returns false.

puts "ruby programming".include?("ruby")

# Output: true

Here, the string "ruby programming" contains "ruby", so the method returns true.

Also, if you want to search "uby", it will still return true because "uby" exists as a part of "ruby" in the string.

6. Split a String into Parts

To break a string into an array of smaller strings, use the .split method.

p "one two three".split

# Output: ["one", "two", "three"]

By default, split divides the string into an array of words using whitespace as the separator.

You can also split by another character, like a comma:

p "apple,banana,grape".split(",")  

# Output: ["apple", "banana", "grape"]

You've already seen common string methods like upcase, length, include?, and gsub.

Here is a quick reference of methods that includes some of those, plus a few more you might find helpful: