Ruby basic

In this page, we cover the essential ruby syntax.

• Variable
• Method
• Class

Variable

foo = "bar"
multiple_words_variable = "using underline"

We use snake_case with multiple words variable.

Method

The following we define a method that takes no parameters.

def method_name
  do_something
end

When calling a method with parameters, we can just type the name.

method_name

The following method definition takes one parameter.

def hello(name)
  puts "hello #{name}"
end

In string, we can use #{} to put variable inside double quoted string.

"hello #{name}"

When we call the method with parameters, we can either use the () or a spaces.

hello "Thomas"
hello("Thomas")

Class

Class are defined in CamelCase.

# Class definition
class Foo
  def hello
    puts "Hello Ruby"
  end
end

Comments line begins with # symbol. The comment valid till the line end.

All methods below the private keywoard are private.

 # Class definition
 class Foo
   def hello
     puts "Hello Ruby"
   end
 
   private
   def internal_method
     do_something
  end
end

Define the method with self. makes it a class method.

def self.another_method
  do_something
end

An initialize method is a constructor method.

# Class definition
class Foo
  def initialize
    init_things_here
  end
end

Here we create instance from a class definition with the new class method.

class Foo
end

obj = Foo.new

@variable with the @ sign is instance variable.

# Class definition
class Foo
  def initialize
    @bar = 123
  end
end

Attribute setting attr_reader allows us to define instance variable with read-only public access.

 class Foo
   attr_reader :bar
   def initialize
     @bar = 123
   end
 end
 
 obj = Foo.new
 obj.bar # returns 123
obj.bar = 456 # error
# NoMethodError: undefined method 'bar='

Did you notice the bar= method?

Here we have instance variable with _read-write- public access with attr_accessor.

class Foo
  attr_accessor :bar
  def initialize
    @bar = 123
  end
end

And we can define custom setter method.

 class Foo
   attr_accessor :bar
   def initialize
     @bar = 123
   end
 
   def b=(value)
     @bar = value
     puts "Setting bar value to #{value}"
  end
end

Let's test our Foo class with custom setter method.

obj = Foo.new
obj.bar # returns 123
obj.b = 321 # able to set bar value
obj.bar # returns 321
obj.b # error
# NoMethodError: undefined method 'b'

What's more? Please go te TryRuby to learn the ruby syntax.

What’s next? We’re going to take a look at “Installing Rails”.