This guide teaches you how to validate the state of objects before they go into the database, using Active Record's validations feature.Ĭallbacks make it possible to write code that will run whenever an object is created, updated, destroyed, etc. Validations are used to ensure that only valid data is saved into your database.

Rather than write schema modifications in pure SQL, migrations allow you to use a Ruby DSL to describe changes to your tables. Migrations are a feature of Active Record that allows you to evolve your database schema over time. This guide will get you started with Active Record models and persistence to the database. Models Active Record BasicsĪctive Record allows your models to interact with the application's database. Let's download the same image using Down.Everything you need to know to install Rails and create your first application. It allows you to avoid these issues to safely and efficiently download files. To solve all of this, Janko created the Down gem. doesn't let you limit redirects or file size.sometimes returns a Tempfile other times StringIO.leaves you vulnerable to remote code execution.Janko Marohnić discovered a bunch of these issues while working on Shrine. It also turns out that open-uri has some other quirks. First up, the above code is not very memory efficient, it loads the entire image into memory and then writes to disk.

The thing is, using open-uri like this is not ideal. Plus, there's a bunch of other potential issues with using open-uri. In practice you would want to handle potential errors, such as a 404 error for a missing image. This is a success, but this was a straightforward example. In the directory in which you opened IRB you will now find the image you downloaded.

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