Default Ruby accessor method?

Question

Hi,

Is there a default method or class accessor that I can add to a Ruby class that get called if a accessor (Ruby like property) doesn't exit? I can then write some custom code to reply from like a array list read from a database where the value can be accessed like a accessor without me writing the accessor code (since if read from a database its unknown).

Using Ruby MRI 1.9

Thank you!

Answer 1

Yes, it's called method_missing; it gets called whenever an undefined method is used. You can use it to add or emulate any method you want, including accessors.

For example, if you throw this on a Hash you can treat the contents of the hash as properties:

h = {}
def h.method_missing(*args)
    if args.length == 1
        self[args[0]]
      elsif args.length == 2 and args[0].to_s =~ /^(.*)=$/
        self[$1.intern] = args[1]
      else
        super
      end
    end

let's you write:

h.bob = "Robert"

and

if h.bill == "William" ...

and so on in addition to the more normal h[:bob] = ... style.