Ruby String Methods

title: 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.
  ruby "Hello".length #=> 5 "Hello World!".length #=> 12

Empty:

• The .empty? method returns true if a string has a length of zero.
  ruby "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.
  ruby "HELLO".count('L') #=> 2 "HELLO WORLD!".count('LO') #=> 1

Insert:

• The .insert method inserts a string into another string before a given index.
  ruby "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.
  ruby "Hello".upcase #=> HELLO

Downcase:

• The .downcase method transforms all letters in a string to lowercase.
  ruby "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.
  ruby "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.
  ruby "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).
  ruby "H-e-l-l-o".split('-') #=> ["H", "e", "l", "l", "o"]
• To split a word in to individual letters :
  ruby "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).
  ruby " 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.
  ruby "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.
  ruby "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.
  ruby "abcde".include?("bc") #=> true "abcde".include?("pqr") #=> false