Does Ruby have a method_missing equivalent for undefined instance variables?

Question

When I invoke a method that doesn't exist, method_missing will tell me the name of the method. When I attempt to access a variable that hasn't been set, the value is simply nil.

I'm attempting to dynamically intercept access to nil instance variables and return a value based on the name of the variable being accessed. The closest equivalent would be PHP's __get. Is there any equivalent functionality in Ruby?

Answer 1

I do not believe this is possible in Ruby. The recommended way would be to use a ''user'' method rather than a ''@user'' instance var in your templates.

This is consistent with the way you deal with Ruby objects externally (''obj.user'' is a method which refers to ''@user'', but is actually not ''@user'' itself). If you need any kind of special logic with an attribute, your best bet is to use a method (or method_missing), regardless if you're accessing it from inside or outside the object.

Answer 2

See my answer to another similar question. But just because you can do it doesn't mean that it's a good idea. Sensible design can generally overcome the need for this kind of thing and allow you to produce more readable and hence maintainable code.

instance_variable_get seems to be the closest equivalent of PHP's __get from what I can see (although I'm not a PHP user).

Looking at the relevant Ruby source code, the only 'missing' method for variables is const_missing for constants, nothing for instance variables.