Using the after_save callback to modify the same object without triggering the callback again (recursion)

Question

If I add an after_save callback to an ActiveRecord model, and on that callback I use update_attribute to change the object, the callback is called again, and so a 'stack overflow' occurs (hehe, couldn't resist).

Is it possible to avoid this behavior, maybe disabling the callback during it's execution? Or is there another approach?

Thanks!

Answer 1

One workaround is to set a variable in the class, and check its value in the after_save.

1. Check it first. (if var)
2. Assign it to a 'false' value before calling update_attribute.
3. call update_attribute.
4. Assign it to a 'true' value.
5. end

This way, it'll only attempt to save twice. This will likely hit your database twice, which may or may not be desirable.

I have a vague feeling that there's something built in, but this is a fairly foolproof way to prevent a specific point of recursion in just about any application. I would also recommend looking at the code again, as it's likely that whatever you're doing in the after_save should be done in before_save. There are times that this isn't true, but they're fairly rare.

Answer 2

Could you use the before_save callback instead?

Answer 3

I didn't see this answer, so I thought I'd add it in case it helps anyone searching on this topic. (ScottD's without_callbacks suggestion is close.)

ActiveRecord provides update_without_callbacks for this situation, but it is a private method. Use send to get access to it anyway. Being inside a callback for the object you are saving is exactly the reason to use this.

Also there is another SO thread here that covers this pretty well: How can I avoid running ActiveRecord callbacks?