CODEWITHSUNDEEP
ruby-on-railsactiverecordpersistence
nfm
nfm

Reputation: 20717

Rails: How do I call `self.save` in my model and have it persist in the database?

I'm trying to keep model logic within my model, but I can't get it to perform modifications on itself and have them persist in the database.

In my controller:

@article.perform_some_calulcations!

In my model:

def perform_some_calculations!
  self.foo.gsub!(/regexp/, 'string')
  self.save
end

If I drop debugger statements into my method and after my call to it in the controller, @article.foo has the correct value. However, when I continue, it doesn't persist in the database and webrick doesn't report any UPDATE statements.

What's going wrong? I don't know if I've ever had to do this before, but surely it's possible right?

Upvotes: 12

Views: 15041

Answers (3)

Shmuli Adelman
Shmuli Adelman

Reputation: 138

I was trying to create a method in a class to modify itself base on an argument. Using .save or .save! did not work for me, but if I used

self.update!({<PROP_NAME>: <NEW_VALUE>})

I saw the changes persisted in my database.

Upvotes: 0

Arsen7
Arsen7

Reputation: 12840

Your problem was that if you modify an attribute "in place", this means: without assigning it a new value, then Rails will think that there is nothing new to be saved, so it "optimizes" the save away.

Each write accessor of your attribute will set a flag, so the save method will know that it should check whether the current value really differs from the value read from the database. That's why self.foo = self.foo.gsub(/regexp/, 'string') works (note that the exclamation mark is not necessary here).

If you need to modify an attribute "in place", for example with gsub! or replace, use:

def perform_some_calculations!
  foo_will_change!
  self.foo.gsub!(/regexp/, 'string')
  self.save
end

Upvotes: 18

Sam 山
Sam 山

Reputation: 42863

Your attributes might be protected. Check your log. IF that is the case then

self.save!

or 

self.save(false)

try taking the exclamation point off your definition.

self.foo = self.foo.gsub!(/regexp/, 'string')

Upvotes: 2

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