rails override default getter for a relationship (belongs_to)
- by brad
So I know how to override the default getters for attributes of an ActiveRecord object using
def custom_getter
return self[:custom_getter] || some_default_value
end
I'm trying to achieve the same thing however for a belongs to association. For instance.
class Foo < AR
belongs_to :bar
def bar
return self[:bar] || Bar.last
end
end
class Bar < AR
has_one :foo
end
When I say:
f = Foo.last
I'd like to have the method f.bar return the last Bar, rather than nil if that association doesn't exist yet.
This doesn't work however. The reason is that self[:bar] is always undefined. It's actually self[:bar_id].
I can do something naive like:
def bar
if self[:bar_id]
return Bar.find(self[:bar_id])
else
return Bar.last
end
end
However this will always make a db call, even if Bar has already been fetched, which is certainly not ideal.
Does anyone have an insight as to how I might have a relationship such that the belongs_to attribute is only loaded once and has a default value if not set.
