Basic Active Record Validations

Salutations!

Let’s play with Active Record Validations! We will start by cloning our user auth project from earlier. I will also add a “validations_start” tag to the resultant project from this project listed below.

I’m sure you know to “Red, Green, Refactor”, but what we really want to remember is “Make a test(RED), Write code to explicitly and exclusively to get that test green (GREEN), then refactor keeping that test green (REFACTOR).” If you are writing feature code with green tests, you are spiking and need to toss all that code once you have learned what you think you need to. If you are refactoring and your tests are getting redder and redder, checkout that last commit and start over.

Validations only work on objects that you are trying to save to the database, objects that are Active Record Objects. Something that we already have in this project that fits this profile is the users/create action. Check out the model for user. Looks like we already have a validation in there from bcrypt! The validator has_secure_password will make sure that you have a password, password confirmation, and that they match. Let’s write a test for those scenarios.

Uhhhh… do we really want to say ‘Oh no bad things!’? Well, sometimes I don’t really have strong feelings on the exact wording on validation errors or whatnot, so “expect” the page to have some sillyness in it. I know that that test will never pass, but will be able to pull the actual error message out once things are wired up correctly. Or, I can actually try and get that to show in the view. Run that test.

Great! A failing test! Now we can write some new code. How do we see that error on the page? Let’s go to the RailsGuides. Click on Guides Index, Active Record Validations, and then scroll down to the chapter 8 link Displaying Validation Errors in Views. Be sure to reference this guide with any little question, as there is a wealth of information here if you understand how to find and read the docs. The more you use the RailsGuides, the more sense they will make to you.

Looks like we need to copy that first code block and edit it! I like to edit down to something like this:

Of course we will be using that validation for @user. Paste that code above your form for registration, and run that test again. Aha! There is the default validation message, and just copy and paste that into your test. Let’s check that out in the browser.

Ew, why are things jumping all around for different error messages? Inspect one of the elements that did not validate… there is a new class on that from our validations code above… Rails automatically adds a div with class="field_with_errors" to each field that does not pass validation… and apparently that div needs some css to not be so greedy with lines. Go to the app/assets/stylesheets/application.css file and add the following:

.field_with_errors {
display: inline-block;
}

You know, let’s also make our error messages a lovely deep red color. Add this to the same css file:

.errors {
color: maroon;
}

Lovely! Let’s check it out in the browser and commit these changes.

Ok! What happens in our browser when we try to register without putting in an email? Whaaaaaaat? That makes no sense whatsoever! You can’t register without putting in a user email! Let’s add a test to our model test.

Cool, we have a failing test! How to we add a validation? Validations go in the model files… open the user model in the model directory. Add the following line:

validates_presence_of :email

Alrighty, run that test. Yay! Let’s check that out in the browser. Oh, thank goodness. And the validation error shows up as we already put that in our view. Perfect! Let’s commit!

So to recap, here is the lowdown on validation errors:

Validation takes place on an Active Record object when you try to create or update that object

Validation constraints are placed in the Active Record object’s model file

Validation errors are generated on the Active Record object by Active Record and Rails (with the first word in the error message being the name of the field, and the message content generated by the type of validation constraint)

Validation errors are placed in a view by calling Active Record methods on the Active Record object containing the error (@object.errors.full_messages.each do |message| ... end) which will be already being passed to the view… you are probably using it in your form_for @object ...