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 returnstrue
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