Freezing Objects | Ruby

Any object can be frozen by invoking Object#freeze. A frozen object can not be modified: we can't change its instance variables, we can't associate singleton methods with it, and, if it is a class or module, we can't add, delete, or modify its methods. 
To test if an object is frozen we can use Object#frozen. It returns true in case the object is frozen, otherwise, return false value. The freeze method in object allows us to turning an object into a constant. 
Note that a frozen object can't be unfreeze. 
 

Syntax: ObjectName.freeze

Below is the example to better understand: 
Example: 
 

# Ruby program of freezing object # define a class class Addition  # constructor method  def initialize(x, y)  @a, @b = x, y  end  # accessor methods  def getA  @a  end  def getB  @b  end  # setter methods  def setA=(value)  @a = value  end  def setB=(value)  @b = value  end end # create an object add = Addition.new(10, 20) # let us freeze this object add.freeze if( add.frozen? )  puts "Addition object is frozen object" else  puts "Addition object is normal object" end # now try using setter methods add.setA = 30 add.setB = 50 # use accessor methods add.getA() add.getB() puts "A is : #{add.getA()}" puts "B is : #{add.getB()}" 

Output : 
 

Addition object is frozen object 
main.rb:20:in `setA=': can't modify frozen Addition (RuntimeError) 
from main.rb:39:in `'

In above example, a class Addition is created then we create an object name is add. by using add.freeze method the object is freeze now we can't change the value of it's method. Here, add.frozen? method is used to show object is freeze or not.