Explanation about Ruby String object

Let's take a look at Ruby's String object using irb.

What is a String object?

An object that handles character strings. Enclose it in single or double quotes to create a String object. Let's check with the class method.

 $ irb
irb(main):001:0> "String".class
=> String

Function of String object

Here are some commonly used methods for String objects.

Uppercase with upcase method

irb(main):002:0> 'String'.upcase
=> "STRING"

Lowercase with downcase method

irb(main):007:0> 'String'.downcase
=> "string"

Cut out characters

You can cut out the specified character string by using the slice method. In the example below, it is cut out from the 0th character to 2 (one before 3).

irb(main):006:0> 'String'.slice(0, 3)
=> "Str"

Check size

irb(main):014:0> 'String'.size
=> 6

Object type conversion

Conversion to integer

Use a method called to_i.

irb(main):018:0> '10000'.class
=> String
irb(main):019:0> '10000'.to_i.class
=> Integer

Conversion to float

Use a method called to_f.

irb(main):020:0> '1.1'.class
=> String
irb(main):021:0> '1.1'.to_f.class
=> Float

Working with String objects

Concatenation of characters

irb(main):027:0> 'Str' + 'ing'
=> "String"

Concatenate characters at the end

irb(main):030:0> 'String' << '!'
=> "String!"

You can also concatenate continuously by using variables.

irb(main):038:0> str = 'String'
=> "String"
irb(main):039:0> str << '!'
=> "String!"
irb(main):040:0> str << '!'
=> "String!!"

Self-substitution

irb(main):042:0> str = 'String'
=> "String"
irb(main):043:0> str += '!'
=> "String!"

Expand variables in strings

If you embed the expression # {variable} in a string enclosed in double quotes Variables can be expanded in strings.

irb(main):047:0> name = 'Masuyama'
=> "Masuyama"
irb(main):048:0> "my name is#{name}is"
=> "My name is Masuyama"

By the way, not only variable expansion but also expression embedding and expansion is possible.

irb(main):052:0> "1 + 1 = #{1+1}"
=> "1 + 1 = 2"