Ruby – Singleton Methods
Last Updated :
03 Jul, 2020
Ruby’s singleton methods are the methods that can be defined for a specific object only i.e. it works for a single object. These kinds of methods belong to the singleton class or eigenclass and are available exclusively for a single object, unlike the other methods which are available for all the instances of the class.
This feature is more useful where there is a need for the object to possess some unique behavior or methods which the other objects of the class do not own.
Syntax:
def Obj.GFG
# Method body
end
Here, the GFG is a singleton method and Obj is an object.
The concept of Singleton methods can be understood by the following examples:
Example 1:
class Vehicle
def wheels
puts "There are many wheels"
end
end
train = Vehicle. new
car = Vehicle. new
def car.wheels
puts "There are four wheels"
end
puts "Singleton Method Example"
puts "Invoke from train object:"
train.wheels
puts "Invoke from car object:"
car.wheels
|
Output:
Singleton Method Example
Invoke from train object:
There are many wheels
Invoke from car object:
There are four wheels
Explanation:
It can be observed that the method wheels have been redefined for the car object of Vehicle class. This wheels method is nothing but a singleton method that shows different behavior for the car.
Example 2:
o1 = String . new
o1 = "GeeksforGeeks"
o2 = String . new
o2 = "GoodExample"
def o2.size
return "Size does not matter"
end
puts "Singleton Method Example:"
puts "Invoke from the object(o1):"
puts o1.size
puts "Invoke from the object(o2):"
puts o2.size
|
Output:
Singleton Method Example:
Invoke from the object(o1):
13
Invoke from the object(o2):
Size does not matter
Explanation:
Singleton method can be defined for the objects which belong to library classes such as String. Instead of printing the size of Object o2, the above code is printing “Size does not matter!” because this is the return value of the o2.size method.
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