There are a couple differences, but they're not big:
.create
is equivalent to .new
followed by .save
. It's just more succinct..create!
is equivalent to .new
followed by .save!
(throws an error if saving fails). It's also just a wee bit shorter.build
is mostly an alias for .new
. It works one way in Rails 3 and another way in Rails < 3.xThe most important part, however, is that these methods can be called through an association (has_many
, etc.) to automatically link the two models.
Although it is correct that create
calls new
and then save
there is a big difference between the two alternatives in their return values.
Save
returns either true
or false
depending on whether the object was saved successfully to the database or not. This can then be used for flow control as per the first example in the question above.
Create
will return the model regardless of whether the object was saved or not. This has implications for the code above in that the top branch of the if
statement will always be executed even if the object fails validations and is not saved.
If you use create
with branching logic you are at risk of silent failures which is not the case if you use new
+ save
.
create!
doesn't suffer from the same issue as it raises and exception if the record is invalid.
The create
alternative can be useful in controllers where respond_with
is used for API (JSON/XML) responses. In this case the existence of errors on the object will cause the errors to be returned in the response with a status of unprocessable_entity
, which is exactly what you want from an API.
I would always use the new
+ save
option for html, especially if you are relying on the return value for flow control.
#create is shorter version of new and save. #create! is throwing exception if validation was not positive.
I'd second the above answers. Plus for create
, one cannot pass false
as an argument which you can do with save
. Passing false
as an argument will skip all rails validations
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