Reverse ( ) Method : This method is used to reverse the entire string.
Example :

    var1 = 'mukesh'
    var2 = 'tomar'
    var3 = '....hello mukesh'
    puts var1.reverse
    puts var2.reverse
    puts var3.reverse
    puts var1 
    puts var2

Output :

hsekum
ramot
hsekum olleh....
mukesh
tomar

As you can see in above method, it doesn't change the original string , it just reverse the entire string .That's var1 is still unchanged even after we called on it .

Another method is string length , using this method we get the number of characters(including spaces) in the string .
Example :

puts 'hello my name is'
name = gets 
puts name.length.to_s // convert num to string
puts name

Output

hello my name is
mukesh tomar // using gets
12
mukesh tomar

Third method is to convert string in lowercase,uppercase,swapcase,capitalize .
Example

name = "mUkesh"
puts name.upcase
puts name.downcase
puts name.swapcase
puts name.capitalize
puts name

Output :

MUKESH
mukesh
MuKeSh
Mukesh
mukesh