Get started with a Rails project in IntelliJ IDEA

Project view

The Project view (Alt+1) on the left side of the IDE displays the project structure. You can use it to open any file in your project, create new files, and so on.

Go to declaration

Go to declaration allows you to navigate to the declaration of a symbol from any symbol usage. To see this capability in action, press Ctrl+Shift+N, start typing users_controller, select the users_controller.rb file and click Enter.

In the opened app/controllers/users_controller.rb file, place the caret next to the User class and press Ctrl+B.

You'll jump to the class declaration in the user.rb file.

Note that you can jump not only to project entities but to definitions within external libraries (which are gems in our case). For instance, keeping Ctrl pressed, hover your mouse pointer over the has_many method. When the method turns into a hyperlink, click it without releasing the key.

IntelliJ IDEA will open the method definition within the ActiveRecord Rails module.

Find usages

Let’s demonstrate the Find usages feature. In the app/controllers/users_controller.rb file, scroll down to the edit action, place the caret next to it and press Alt+F7. In the Find window, you can explore the places where this action is used.

Navigate between Rails entities

When working on a specific Rails entity, like a controller, you can navigate to the related view, model, test, or helper. Place the caret next to edit method, press Ctrl+Alt+Home, select View and press Enter. IntelliJ IDEA will open the edit.html.erb file containing the corresponding view.

You can use the same shortcut within a view or use the icon in the editor gutter to quickly go to the corresponding action.

Search everywhere

The next IntelliJ IDEA feature allows you to search for files, classes, symbols, or options and jump to the entity you need.

Let’s try to find the destroy action within UsersController. Press Shift twice and start typing destroy. IntelliJ IDEA lists all of the found results where your query is found. Select the destroy action from UsersController and press Enter.

The users_controller.rb file will be opened and the caret will be placed on the definition of the destroy action.

Code completion

IntelliJ IDEA can help you complete the names of classes, methods, keywords, and so on. When you invoke code completion, IntelliJ IDEA analyses the context and suggests the choices applicable to the current caret position.

For instance, open the users_controller.rb file and go to the index method declared in the UsersController class. Type the following code inside the method...

... and then type dot. Because the User class is inherited from the ApplicationRecord module, the editor will display all inherited members.

After that, start typing first to filter the list and find the corresponding member from the Querying module, and press Enter.

Intentions

Intentions help you to quickly apply various code changes: convert statements for better code style, add strings to locale dictionaries, use language injections, and so on.

To see intentions in action, open the user.rb file and scroll down to the User.digest method, which uses a multiline ternary operator (?:). According to the Ruby Style Guide, it is preferable to replace such operator with the if/then/else/end block. To do this, place the caret at this ternary expression (for instance, next to ActiveModel) and press Alt+Enter. Press Enter to convert a ternary operator to the if/then/else/end block.

Note that you can check your code and detect possible issues using inspections.

Refactor code

Refactoring is the process of modifying source code in order to make it easier to maintain and extend, but without changing its behavior. Let’s look at some refactoring features available in IntelliJ IDEA.

Rename refactorings allow you to rename classes, methods, files, variables, and parameters with all the references to them in the code corrected accordingly. Open the users.rb file and scroll down to the downcase_email method raised in the before_save ActiveRecord callback. Place the caret next to this method and press Ctrl+Shift+I to see its definition.

Click Esc and press Ctrl+Alt+Shift+T. Select Rename in the invoked popup, which suggests various refactorings.

In the Rename dialog, specify a new method name (lowercase_email in our case) and click Refactor.

The Refactor Preview window will display all references to the renamed method.

Click Do Refactor to rename the method in all places.

Extract variable

The Extract Variable refactoring puts the result of the selected expression into a variable. It declares a new variable and uses the expression as an initializer. The original expression is replaced with the new variable.

Open the user.rb file and go to the feed method. In this method, we can extract an SQL subquery to a variable. To do this, select a corresponding substring and press Ctrl+Alt+V. Then, specify the variable name and press Enter to finish extracting.

Reformat code

IntelliJ IDEA allows you to reformat source code to meet the requirements of your code style.

Let's reformat the code of the user.rb file. Open this file and press Ctrl+Alt+L.

IntelliJ IDEA will reformat the entire file and display a number of changed lines.

Run all tests

Our project contains Minitest tests in the test folder. To run all tests, open the Project view by pressing Alt+1. Then, right-click the test folder and select Run 'All tests in test' from the context menu.

IntelliJ IDEA will run and display test results in the Run tool window.

Run specific tests

Now let’s see how to run a specific test. Open the users_controller_test.rb file, scroll down to the should redirect index when not logged in test and click the Run button on the left gutter next to this test.

In the invoked menu, select Run ‘Minitest: test_should_redirect_index...’. IntelliJ IDEA will display the result for this test.

Rerun failed tests

Now let’s go back to users_controller_test.rb and break two tests. For the should get new and should redirect index when not logged in tests comment the get_sighup_path and get users_path lines. To do this, select these lines and use the Ctrl+/ shortcut.

Run all tests again as described in Run all tests. You can see now that these tests failed.

Let’s fix these tests in the currently opened users_controller_test.rb file by uncommenting the get_sighup_path and get users_path lines Ctrl+/. We can now rerun only these failed tests using the button.

Set a breakpoint and start debugging

First, open the users_controller.rb file. Set a breakpoint within the create method next to the line where a new user is created.

To start debugging, press Ctrl twice and start typing sample_rails_app. Select the Development: sample_rails_app configuration from the list, hold down the Shift key (the dialog title will be changed to Debug), and press Enter.

If the debase and ruby-debug-ide gems required for debugging have not been installed yet, IntelliJ IDEA suggests installing them.

After installing the gems, the Debug tool window will show the application output.

Open a browser on the local machine and specify the application address 0.0.0.0:3000.

Click the Sign up now! button. On the Sign up page, enter your credentials and click Create my account.

The program will stop when it reaches the breakpoint.

Examine variables

You can now examine the application state and the values of variables.

The Frames pane displays the application threads and the corresponding call stacks. In our case, the create method is called in Thread 30. The Variables pane allows you to examine variables available in the current context.

Let’s add the user_params variable to the list. Click the button in the Variables pane and start typing user_params. Select the user_params variable in the invoked drop-down and press Enter.

Then, click the button next to this variable and then expand the @parameters variables in the same way. You can see the user credentials specified in the Sign up form.

Once the breakpoint is hit, we can step through the code.

Step over

Step over proceeds to the next line in the current scope (for example, goes to the next line), without descending into any method calls on the way.

On the screen below, you can see that the User object is not created yet and the @user variable not initialized (equals nil).

Press F8 or click the button in the Debug window toolbar. The debugger will go to the next line - the if statement. In the editor and Variables pane, you can see that the @user variable was initialized.

Use the button to examine @user properties.

Step into

Step into will cause the debugger to descend into the method calls or blocks on the current line and follow them through. If there are multiple method calls or blocks, you can choose the desired target.

Click the button to resume program execution. Go to the browser again and create another user in the Sign up form. The script will stop when it reaches the line where a user is created.

Press F7 or click the button. The editor will set a focus on the user_params method. You can use arrow keys or Tab to choose the desired method to step into (new or user_params in the example below). Select user_params and press Enter. The program execution will jump to the user_params method definition.

If you press F7 another time, the debugger will suggest selecting between the params and require methods from the StrongParameters module.

Debug in console

The debugger has the Console tab that enables you to interact with a debugged application with an IRB-like console.

Start typing user_params in the console, select the corresponding variable and press Enter.

The Console window will display the values of variables.