Selective runtime provision of instance methods


#1

I’d like to get some comments and suggestions from anyone who may have
an opinion on this or know of a better way to accomplish this.

I have an object with a lot of methods and variables some of which (but
not all) I’d like to make callable from another object that happens to
be evaluated by ERB. So I did this:

class LotsOfMethods # to be made callable def method1 ... end def method2 ... end ...
# not callable
def methodX ... end

def delegate
    d = OpenStruct.new({
        :var1 => var1,
        :var2 => var2,
        ...
        })

    my = self
    d_singleton = class << d; self end
    d_singleton.send(:define_method, :method1) { my.method1 }
    d_singleton.send(:define_method, :method2) { my.method2 }
    ...

    d
end

end

class Sandbox
def self.env(delegate)
Proc.new {}
end
end

sacred_object = LotsOfMethods.new
output = ERB.new(text).result(Sandbox.env(sacred_object.delegate))

The idea is that the embedded Ruby code in “text” will be able to
access the specified variables and methods in ‘delegate’ but not any
others. So, for example:

text = ‘<%= delegate.method1 %>’

will be allowed; but:

text = ‘<%= delegate.methodX %>’

will raise an exception.

Does anyone know of a better way to accomplish the same effect?

Best regards,

Julian I. Kamil removed_email_address@domain.invalid
http://pandora.rubyveil.com/ - Pandora Publisher
http://books.rubyveil.com/ - The Ruby Bookshelf