Add method to object

Using ruby metaprogramming always we can add instance variable & method to specific object.

# Example 2: create a new instance of class Object
my_object = Object.new

# create a second instance of class Object
my_other_object = Object.new

# define a method on my_object to set the instance variable @my_instance_variable
def my_object.set_my_variable=(var)
  @my_instance_variable = var
end

# define a method on my_object to return value of instance variable @my_instance_variable
def my_object.get_my_variable
  @my_instance_variable
end

my_object.set_my_variable = "Hello"
my_object.get_my_variable # => Hello

my_other_object.get_my_variable = "Hello" # => NoMethodError

Rails info:

Some rails quick info that will help you to think in new way

• request.format It return request format like :html, :json, :pdf... we can use this like:

if request.format.symbol == :html
   .....
else
    ......
end

• foo = true and false #foo is true beacuse for assign = prioritty is greater then and
• every ruby block and statement return value even class

var = class Foo
  4
end

For above code the value of vae is 4 beacuse class declaretion return 4.

• An object is composed of a bunch of instance variables and a link to a class.

• The methods of an object live in the object’s class (from the point of view of the class, they’re called instance methods).

• The class itself is just an object of class Class. The name of the class is just a constant.

• Class is a subclass of Module. A module is basically a package of methods. In addition to that, a class can also be instantiated (with new( )) or arranged in a hierarchy (through its superclass( )).

• Constants are arranged in a tree similar to a file system, where the names of modules and classes play the part of directories and regular constants play the part of files.

• Each class has an ancestors chain, beginning with the class itself and going up to BasicObject.

• When you call a method, Ruby goes right into the class of the receiver and then up the ancestors chain, until it either finds the method or reaches the end of the chain.

• Every time a class includes a module, the module is inserted in the ancestors chain right above the class itself.

• When you call a method, the receiver takes the role of self.

• When you’re defining a module (or a class), the module takes the role of self.

• Instance variables are always assumed to be instance variables of self.

• Any method called without an explicit receiver is assumed to be a method of self.

• Ruby example intrview question with answer