Question

obj.update_attribute(:only_one_field, 'Some Value')
obj.update_attributes(field1: 'value', field2: 'value2', field3: 'value3')

Both of these will update an object without having to explicitly tell ActiveRecord to update.

Rails API says:

update_attribute

Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default.

update_attributes

Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned.

So if I don’t want to have the object validated I should use #update_attribute. What if I have this update on a #before_save, will it stackoverflow?

My question is does #update_attribute also bypass the before save or just the validation.

Also, what is the correct syntax to pass a hash to #update_attributes … check out my example at the top.

Answer 1

Please refer to update_attribute. On clicking show source you will get following code

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2614
2614:       def update_attribute(name, value)
2615:         send(name.to_s + '=', value)
2616:         save(false)
2617:       end

and now refer update_attributes and look at its code you get

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2621
2621:       def update_attributes(attributes)
2622:         self.attributes = attributes
2623:         save
2624:       end

the difference between two is update_attribute uses save(false) whereas update_attributes uses save or you can say save(true).

Sorry for the long description but what I want to say is important. save(perform_validation = true), if perform_validation is false it bypasses (skips will be the proper word) all the validations associated with save.

For second question

Also, what is the correct syntax to pass a hash to update_attributes… check out my example at the top.

Your example is correct.

Object.update_attributes(:field1 => "value", :field2 => "value2", :field3 => "value3")

or

Object.update_attributes :field1 => "value", :field2 => "value2", :field3 => "value3"

or if you get all fields data & name in a hash say params[:user] here use just

Object.update_attributes(params[:user])