Ruby - Class Freezing Objects

Introduction

You can explicitly prevent an object from being extended it by "freezing" it using the freeze method:

ob.freeze

Any attempt to extend this object further would result in a runtime error:

module D
    def method_d
        puts( 'hello from d' )
    end
end
ob.extend( D ) #=> Error: can't modify frozen object (RuntimeError)

You can use the frozen? method to test whether an object has been frozen:

if !(ob.frozen?)
    ob.extend( D )
    ob.method_d
else
    puts( "Can't extend a frozen object" )
end

• Previous
• Next