freeCodeCamp/guide/english/ruby/ruby-string-methods/index.md

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Ruby String Methods

Ruby String Methods

Ruby has many built-in methods to work with strings. Strings in Ruby by default are mutable and can be changed in place or a new string can be returned from a method.

Length:

• The .length method returns the number of characters in a string including white-space.

  "Hello".length #=> 5
  "Hello World!".length #=> 12
  

Empty:

• The .empty? method returns true if a string has a length of zero.

  "Hello".empty? #=> false
  "!".empty?     #=> false
  " ".empty?     #=> false
  "".empty?      #=> true
  

Count:

• The .count method counts how many times a specific character(s) is found in a string.
• This method is case-sensitive.

  "HELLO".count('L') #=> 2
  "HELLO WORLD!".count('LO') #=> 1
  

Insert:

• The .insert method inserts a string into another string before a given index.

  "Hello".insert(3, "hi5") #=> Helhi5lo # "hi5" is inserted into the string right before the second 'l' which is at index 3
  

Upcase:

• The .upcase method transforms all letters in a string to uppercase.

  "Hello".upcase #=> HELLO
  

Downcase:

• The .downcase method transforms all letters in a string to lowercase.

  "Hello".downcase #=> hello
  

Swapcase

• The .swapcase method transforms the uppercase latters in a string to lowercase and the lowercase letters to uppercase.

  "hELLO wORLD".swapcase #=> Hello World
  

Capitalize:

• The .capitalize method make the first letter in a string uppercase and the rest of the string lowercase.

  "HELLO".capitalize #=> Hello
  "HELLO, HOW ARE YOU?".capitalize #=> Hello, how are you?
  

Note that the first letter is only capitalized if it is at the beginning of the string. ruby "-HELLO".capitalize #=> -hello "1HELLO".capitalize #=> 1hello

Reverse:

• The .reverse method reverses the order of the characters in a string.

  "Hello World!".reverse #=> "!dlroW olleH"
  

Split:

• The .split takes a strings and splits it into an array, then returns the array.

  "Hello, how are you?".split #=> ["Hello,", "how", "are", "you?"]
  

• The default method splits the string based on whitespace, unless a different separator is provided (see second example).

  "H-e-l-l-o".split('-') #=> ["H", "e", "l", "l", "o"]
  

• To split a word in to individual letters :

  "hello".split("") #=> ["h", "e", "l", "l", "o"]
  

Chop:

• The .chop method removes the last character of the string.

• A new string is returned, unless you use the .chop! method which mutates the original string.

  "Name".chop #=> Nam
  

  name = "Batman"
  name.chop
  name == "Batma" #=> false
  

  name = "Batman"
  name.chop!
  name == "Batma" #=> true
  

Strip:

• The .strip method removes the leading and trailing whitespace on strings, including tabs, newlines, and carriage returns (\t, \n, \r).

  "  Hello  ".strip #=> Hello
  

Chomp:

• The .chomp method removes the last character in a string, only if it’s a carriage return or newline (\r, \n).
• This method is commonly used with the gets command to remove returns from user input.

  "hello\r".chomp #=> hello
  "hello\t".chomp #=> hello\t # because tabs and other whitespace remain intact when using `chomp`
  

To Integer:

• The .to_i method converts a string to an integer.

  "15".to_i #=> 15 # integer
  

Gsub:

• gsub replaces every reference of the first parameter for the second parameter on a string.

"ruby is cool".gsub("cool", "very cool") #=> "ruby is very cool"

• gsub also accepts patterns (like regexp) as first parameter, allowing things like:

"ruby is cool".gsub(/[aeiou]/, "*") #=> "r*by *s c**l"

Concatenation:

• Ruby implements some methods to concatenate two strings together:

• The + method:

"15" + "15" #=> "1515" # string

• The << method:

"15" << "15" #=> "1515" # string

• The concat method:

"15".concat "15" #=> "1515" # string

Index:

• The index method returns the index position of the first occurrance of the substring or regular expression pattern match in a string.

• If there is no match found, nil is returned.

• A second optional parameter indicates which index position in the string to begin searching for a match.

  "information".index('o') #=> 3
  "information".index('mat') #=> 5
  "information".index(/[abc]/) #=> 6
  "information".index('o', 5) #=> 9
  "information".index('z') #=> nil
  

Clear:

• Removes string content.

  a = "abcde"
  a.clear    #=> ""
  

Include?:

• Returns true if the string contains the given string or character as an argument.

  "abcde".include?("bc")  #=> true
  "abcde".include?("pqr") #=> false