has_many使用类与类名

Question

I've been modelling some custom has_many associations like this:

has_many :friends, class: User

I recently found that this style isn't documented and the API docs:

has_many :friends, class_name: 'User'

I haven't noticed any problems with the former syntax, and I'm curious why the later syntax is used (wouldn't it be better to avoid converting the string to a class?). Any reason to switch from the former to the later?

Answer 1

Well in coming version of rails class has been renamed to anonymous_class . Although it is still in the master branch. There is a problem with the use of :class and here it goes from the commit :

In 1f006c an option was added called :class to allow passing anonymous classes to association definitions. Since using :class instead of :class_name is a fairly common typo even amongst experienced developers this can result in hard to debug errors arising in raise_on_type_mismatch?

To fix this we're renaming the option from :class to :anonymous_class as that is a more correct description of what the option is for. Since this was an internal, undocumented option there is no need for a deprecation.

It is in 4-2-stable

Rename :class to :anonymous_class in association options. Fixes #19659

Answer 2

If you needed to define a class dynamically or run a method that would return a class then the first option would be useful.

Honestly though I can't think of a good scenario in which that would be an ideal approach.