Similar to a person having multiple facets to their personality, and depending on the circumstance or situation depends on how and which facet is shown in that circumstance or situation, self allows us to call on itself in various ways dependent on the context in which the self keyword is used within our code.
When self is called outside of a block of code, it will be identified as the global object itself, for example:
puts “Self’s class is #{self.class}.”```
outputs: Self’s class is Object.```
self when called inside of a class defines the class name as the class.
class Horoscope
puts "Self is #{self}."
end
outputs:
Self is Horoscope.
We could also replace self with Horoscope here and our output would remain the same as they are interchangeable when called within a class.
class Horoscope
puts "Self is #{Horoscope}."
end
outputs:
Self is Horoscope.
Going a step further, if we define a class variable within our class, we can then call that class variable within a method that calls on itself.
class Horoscope
@@sign = "Aquarius"
def self.name
puts "Self inside class method is: #{self}."
return @@sign
end
end
puts "Horoscope class method name is: #{Horoscope.name}."
outputs:
Self inside class method is: Horoscope.
Horoscope class method name is: Aquarius.
Note we must explicitly return our class variable @@sign within our self.name method, otherwise when we try to interpolate and call Horoscope.name outside of the class, nothing will print to the screen as we have not set a return value for the method.
Lastly, we can define self as an instance of a class method, however in order to obtain any information from it we will need to create a new instance of the class.
class Horoscope
def sign
puts "Self inside the instance method is: #{self}."
puts "Self.class inside the instance method is #{self.class}."
return "Aquarius"
end
end
horoscope = Horoscope.new
puts "Horoscope instance method 'sign' is: #{horoscope.sign}."
outputs:
Self inside the instance method is: #<Horoscope:0x00005599135f5e40>.
Self.class inside the instance method is Horoscope.
Horoscope instance method 'sign' is: Aquarius.
Here #{self} displays the object that was instantiated when we called .new on the Horoscope class. #{self.class} tells us the name of the parent class in which self was called from. #{horoscope.sign} outputs the value we set when setting the return value to “Aquarius” within the sign method.