How do I dynamically define a class in Ruby WITH a name?
I know how to create a class dynamically without a name using something like:
dynamic_class = Class.new do
def method1
end
end
But you can't specify a class name. I want to create a class dynamically with a name.
Here's an example of what I want to do but of course it doesn't actually work.
(Note that I am not creating an instance of a class but a class definition)
class TestEval
def method1
puts "name: #{self.name}"
end
end
class_name = "TestEval"
dummy = eval("#{class_name}")
puts "dummy: #{dummy}"
dynamic_name = "TestEval2"
class_string = """
class #{dynamic_name}
def method1
end
end
"""
dummy2 = eval(class_string)
puts "dummy2: #{dummy2}" # doesn't work
Actual output:
dummy: TestEval
dummy2:
Desired output:
dummy: TestEval
dummy2: TestEval2
======================================================
Answer: A totally dynamic solution using sepp2k's method
dynamic_name = "TestEval2"
Object.const_set(dynamic_name, Class.new) # If inheriting, use Class.new( superclass )
dummy2 = eval("#{dynamic_name}")
puts "dummy2: #{dummy2}"
The name of a class is simply the name of the first constant that refers to it.
I.e. if I do myclass = Class.new
and then MyClass = myclass
, the name of the class will become MyClass
. However I can't do MyClass =
if I don't know the name of the class until runtime.
So instead you can use Module#const_set
, which dynamically sets the value of a const. Example:
dynamic_name = "ClassName"
Object.const_set(dynamic_name, Class.new { def method1() 42 end })
ClassName.new.method1 #=> 42