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.

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

"Hello".length
# returns: 5

"Hello World!".length
# returns: 12

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

"HELLO".count('L')  
# returns: 2

"HELLO WORLD!".count('LO')  
# returns: 1

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

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

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

"Hello".upcase
# returns:
HELLO

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

"Hello".downcase
# returns:
hello

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

"HELLO".capitalize
# returns:
Hello

"HELLO, HOW ARE YOU?".capitalize
# returns:
Hello, how are you?

Note that the first letter is only capitilized if it is at the beginning of the string.

"-HELLO".capitalize
"1HELLO".capitalize
# returns:
-hello
1hello

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

"Hello World!".reverse
# returns:
"!dlroW olleH"

• The .split takes a strings and splits it into an array, then returns the array.
• The default method splits the string based on whitespace, unless a different separator is provided (see second example).

"Hello, how are you?".split
# returns:
["Hello,", "how", "are", "you?"]

"H-e-l-l-o".split('-')
# returns:
["H", "e", "l", "l", "o"]

• 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
# returns:
Nam

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

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

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

"  Hello  ".strip
# returns:
Hello

• 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
# returns:
hello

"hello\t".chomp
# returns:
hello\t #because tabs and other whitespace remain intact when using `chomp`

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

"15".to_i
# returns:
15 #integer