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.
Also note that
- Validation is skipped.
- Callbacks are invoked.
- updated_at/updated_on column is updated if that column is available.
- Updates all the attributes that are dirty in this object.
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.
Examples:
[codesyntax lang=”rails”]
Object.update_attribute(:only_one_field, "Some Value") Object.update_attributes(:field1 => "value", :field2 => "value2", :field3 => "value3") Object.update_attributes(params[:user])
[/codesyntax]
All of these will update an object in a database without having to explicitly tell AR to update.
update_attribute can update only one column.
Validation
Use update_attribute to skip validations.
update_attribute uses save(false) while update_attributes uses save (which means save(true)).
Callbacks
If perform_validation is false while calling save then it skips validation, and it also means that all the before_* callbacks associated with save.
Update attributes in database without saving
update_column(name, value)
Updates a single column in a database, without calling save. It will run SQL script in database: “UPDATE tablename SET name=value WHERE id=X”
- Validation is skipped.
- Callbacks are skipped.
- Save method is NOT called, but it updates record in the database.
- updated_at column is not updated (if the column is available).
- Raises an
ActiveRecordErrorwhen called on new objects, or when thenameattribute is marked as readonly.
update_column is equivalent to update_columns(name => value), which can update multiple columns in database.
.attributes property
Use .attributes to update attributes of the model without saving it to a database.
[codesyntax lang=”rails”]
@car = Car.new(:some_field=>'value', :another_field=>'value')
#
@car.attributes = {:title => 'Toyota', :year => 2005, :used=>false}
#other processing
..
#finally, save to DB
@car.save
[/codesyntax]
Ref.
Discussions on StackOverflow:
http://stackoverflow.com/questions/2778522/rails-update-attribute-vs-update-attributes
Jérémy Mortelette says:
@object.attributes help me so much ! Thank you for this really good post !!!
Hunter Stevens says:
Pleas update this post. You initially say that `update_attribute` updates the `updated_at` field (if present). You then later say that it DOES NOT update this field.
Anonymous says:
in first case it is ‘update_ATTRIBUTE’ and in the seconda case it is ‘update_COLUMN’. Those are two different methods.
I updated description of ‘update_column’ to make it more clear what it does.