Ruby-on-rails – The differences between .build, .create, and .create! and when should they be used


So I've been seeing people using .build, .create, and .create! within their controllers more and more lately. What's the difference from just using .new and passing the param'd object and then .save? Are there pros and cons? Does using these other methods offer benefits?

Best Solution

There are a couple differences, but they're not big:

  1. .create is equivalent to .new followed by .save. It's just more succinct.
  2. .create! is equivalent to .new followed by .save! (throws an error if saving fails). It's also just a wee bit shorter
  3. I think .build is mostly an alias for .new. It works one way in Rails 3 and another way in Rails < 3.x

The most important part, however, is that these methods can be called through an association (has_many, etc.) to automatically link the two models.

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