Rails - how to use reload method?

Question

Case1: Creating a new record for a model with assigning the associated object(Status object instead of Status.id) like

    visit = Visit.create(:date => Date.today, :status => Status.first)
    visit.status_id #=> 1

After creating the record

I'm trying to update the attribute 'status_id' (Status.id instead of Status object) but it returns the old value even calling reload after save the object. Example:

    visit.status_id = Status.last.id
    visit.save
    visit.reload
    visit.status_id #=> 1

When I calling reload method after create it is working as expected

    visit = Visit.create(:date => Date.today, :status => Status.first)
    visit.status_id #=> 1
    visit.reload
    visit.status_id = 2
    visit.save
    visit.status_id #=> 2

Case2: If I assigning the 'status_id' value instead of Status object, then no need to reload object and its working fine

    visit = Visit.create(:date => Date.today, :status_id => Status.first.id)
    visit.status_id #=> 1
    visit.status_id = 2
    visit.save
    visit.status_id #=> 2

Using the two cases above, when should I use the reload method? Should it be before or after save?

Solution

I think your understanding of how save and reload work is basically correct. Your results certainly seem to be inconsistent. I have a feeling based on your results that your save is failing.

save will try to store the local version to the database. It does not refresh any values from the database if the model has changed since you loaded it. If the save fails, the local values are still whatever you set them to, but the database will have the old values.

reload overwrites any local changes you have made and sets them to the database values.

Assuming there is no contention on the database for the models you are concerned with, let's walk through your examples.

Example 1 If the save works, then the reload will not do anything and the value of visit.status_id will be Status.last.id. However, if the save fails then the value of visit.status_id will be whatever it was in the database originally.

Example 2 If the create does not work then the reload would give a RecordNotFound error because you can't reload something that hasn't been persisted. After that you set the status_id to 2 and then call save. Whether the save succeeds or fails, the local value of status_id will remain as 2. However, the database value depends on whether it passed or failed.

Example 3 Hey! This is the same as example 2 except for the reload.

Here is some documentation, but I'm not sure how helpful you will find it: http://apidock.com/rails/ActiveRecord/Persistence/save

http://apidock.com/rails/ActiveRecord/Persistence/reload

You might want to check for save success or call save! to ensure the save is actually working.

I hope that helps.

Comments

[nishanthan]

Thanks for the answer, according to ur example 1 when i'm saving the record in console it returns true and also there is no any errors for the object(table has the new record), now i'm updating the value (without reloading the record) it is not updated, If the updation should done, i've to reload and then edit the value then the record is updated with new value