Customizing Rails error messages for models and attributes

Raising errors for required and permitted attributes makes it easier to find errors in your application during development and in tests. Consider this approach if you want to strengthen the [params handling](https://makandracards.com/makandra/1904...

In the past we validate and set default values for boolean attributes in Rails and not the database itself.

Reasons for this:

• Older Rails didn't s...

Specify these gem versions in your Gemfile:

gem 'cucumber', '~> 1.3.0'
gem 'cucumber-rails', '= 0.3.2' # max version for Rails 2
gem 'capybara', '< 2' # capybara 2+ requires Rails 3
gem 'mime-types', '< 2' # dependeny of capybara

...

If validations failed for a record, and you want to find out if a specific validation failed, you can leverage ActiveModel's error objects.
You rarely need this in application code (you usually just want to print error messages), but it can be u...

You've been there: A form cannot be submitted, but you don't see a validation error because the field at fault has no corresponding input field on the form. Because this is usually a bug, you insert debug information listing all errors into the fo...

When HTTP clients make an request they can define which response formats they can process. They do it by adding a header to the HTTP request like this:

Accept: application/json

This means the client will only understand JSON respon...

Let's say we have posts with an attribute title that is mandatory.

Our example feature request is to tag these posts with a limited number of tags. The following chapters explain different approaches in Rails, how you can assign such a...

For Rails models where only one of multiple attributes may be filled out at the same time, there is no built-in validation.

I've seen different solutions in the wild, each with different downsides:

• Private method referenced via validate: wor...

This card explains how to generate an entity relationship diagram for your Rails application.
We also show how to limit your ERD to a subset of models, e.g. models inside a namespace.

Generating a full ERD

Option A: RubyMine

1. Right-cli...