How can I add a field dynamically to a Java class using Groovy?

Question

In Ruby I can add instance variables to a class by opening it, and doing something like this :


class Whatever
   def add_x
     @x = 20
   end
end

and this would add me an instance variable by the name of x. How can I do the same thing in Groovy?

hohonuuli · Accepted Answer · 2009-08-03 20:24:57Z

3

You can use Groovy's metaclass:

class Foo { String bar }
f = new Foo(bar:"one")
f.metaClass.spam = "two"
f.spam == "two" // returns true
f.spam = "eggs" // Change property value
f.spam == "eggs" //returns true

answered Aug 3, 2009 at 20:24

hohonuuli

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1 Comment

hohonuuli Over a year ago

NOTE: This only adds the variables to a particular instance of a class.

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