IntelliJ IDEA 2018.2 Help

Work with Scala code in the editor

IntelliJ IDEA lets you use different Scala intention actions, convert your code from Java to Scala, and use different Scala templates while working in the IntelliJ IDEA editor.

Strings in Scala

You can add different intentions for strings, perform different actions, and set a different format for multi-line strings.
Check the following examples:

  • Insert gap with concatenation ("+ +") into a string.
  • Convert a string into a multi-line string using the Convert to """string""" intention and vice versa.
    1. Enter your string, press Alt+Enter and from the drop-down list of intentions, select Convert to """string""".
    2. You also can convert the multi-line string into the regular string. Press Alt+Enter to open the drop-down list of intentions. Select Convert to "string" and press Enter. View the result.
    3. To enter a multi-line string, simply type triple quotes in your editor. If you press Enter, it will automatically invoke the stripMargin method. The stripMargin method removes the left-hand part of a multi-line string up to a specified delimiter. The white spaces are also preserved.
  • Add the .replace("\r"," ") intention. This intention lets you keep the caret in the correct place on the next line in the multi-line strings regardless of what operating system you have at the moment.

    Simply enter a multi-line string, press Alt+Enter and select the appropriate intention from the drop-down list.

    add replace intention
  • Use the Inject Language/Reference intention to insert a language or a reference into your multi-line string literals. For more information, please refer to the Language Injections documentation.
  • Use the Multi-line stings tab in Scala settings to set a different format for multi-line strings' options such as Margin char indent or disable a multi-line strings support.
    1. In the main menu, select File | Setting | Editor | Code Style | Scala.
    2. On the Scala page, select the Multi-line strings tab.
      multi line strings
    3. Edit the settings and click OK.
  • Turn simple string into the interpolated one adding a variable reference.

Implicit hints

IntelliJ IDEA lets you enable, expand and collapse editor hints for implicit conversions and arguments to help you read your code.

  1. On the main toolbar, select View | Show Implicit Hints.
  2. In the editor, right-click the hint and from the pop-up menu, select the appropriate action in order to expand the existing hint, disable the mode, or to see the implicit arguments.
    implicits pop up

Alternatively, while in the editor, you can press Ctrl+Shift+Alt++ to enable the implicit hints. If you press the same shortcut again, IntelliJ IDEA expands the implicit hints to show you more detailed information. Press Ctrl+Shift+Alt+- to collapse the hints.

Implicit conversions

IntelliJ IDEA lets you invoke implicit conversion methods and arguments.

Convert method implicitly

  1. Select an expression and press Shift+Ctrl+Q (Ctrl+Q for macOS) to invoke the list of applicable implicit conversions. The list shows the regular scope displayed on the top and the expanded scope that is displayed on the bottom of the list.
    choose implicit conv
  2. If you need, make the implicit conversion method explicit. Press Alt+Enter and select Make explicit or Make explicit (Import method).
    choose implicit with make exp
    • If you select Make explicit then IntelliJ IDEA returns a method call with the class name. It might be helpful if you need to make sure that the compiler imports a particular implicit conversion method that you originally wanted:
      make explicit
    • If you select Make explicit (Import method) then the method is imported statically and IntelliJ IDEA returns just its call without the class name. Also, the next time you open the list of useful implicit conversions you will see this method in the regular scope:
      make explicit import met

Convert argument implicitly

  1. Place a cursor to the method where implicit conversion was used and press Ctrl+Shift+P to invoke implicit arguments. It might be helpful for code analyzing when you want to find out what implicit arguments were passed to the particular call. IntelliJ IDEA also lets you view the recursive implicit arguments.
    implicit arguments
  2. If IntelliJ IDEA cannot find method calls where implicit parameters were passed, it displays a pop-up message:
    no implicit param

Type Info action

IntelliJ IDEA lets you work with type inferences using the Scala Show Type Info action:

  • To invoke the Show Type Info action in the editor, navigate to the value and press Alt+Equals or ⌃⇧P (for Mac OS):
    type info string
  • You can also see the type information on a value definition. Simply put the caret on a value definition and press Alt+Equals or ⌃⇧P (for Mac OS):
    type info int
  • To add a type annotation, highlight the value, press Shift+Enter and from the context menu select Add type annotation to value definition: As a result, the type annotation is added.
    To remove the type annotation, press Shift+Enter and select Remove type annotation from value definition.

Code completion

You can use code completion for the following actions:

  • To import classes, press Shift+Enter on the code in question, select Import class. However, in lots of cases IntelliJ IDEA recognizes what you need to import and displays a list of suggestions.
  • A name-based type suggestion for parameters. IntelliJ IDEA lets you automatically complete both the name and the type before actually adding a type reference.
    scala type suggestions
  • Invoke the Convert to interpolated string intention.
    You can easily convert a regular string into the interpolated one using code completion after $.
    Alternatively, select a value with concatenation in your string, press Alt+Enter and select Convert to interpolated string.
  • If you have sealed types with inheritors, Java Enums, and Scala Enumerations, you can generate an exhaustive match checking for them. Note that autocompletion is available.
    sc match exhaustive
    As a result, the compiler checks a pattern match for all possible members of a sealed type.
    sc mathc exaustive result

Create from usage

IntelliJ IDEA lets you create new code elements without declaring them first:

  1. In the editor, type a name of a new code element and press Alt+Enter.
  2. From the list of intentions, select the one you need.
    create from usage
    Press Enter.

Structure view

IntelliJ IDEA lets you view a structure of your code:

  • To open the Structure tool window, press Alt+7.
    view code structure
  • To navigate from the Structure tool window to the code item in the editor, press F4.
    To simply highlight the code, press Ctrl+Enter.

Java-to-Scala code conversion

IntelliJ IDEA lets you convert Java code into Scala:

  1. Copy your Java code (expression, method, class) and paste it into a Scala file.
  2. IntelliJ IDEA displays the Convert the code from Java dialog suggesting a conversion. Click OK.

If you do not want to use the copy/paste actions, you can open your Java file in the editor and select Refactor | Convert to Scala or press Ctrl+Shift+G.

In this case IntelliJ IDEA will create a Scala file with the converted code.

Scala generate actions

Use Alt+Insert to generate actions such as override, delegate, or implement methods.

generate menu

For example, select the Override methods action. IntelliJ IDEA displays a dialog with the list of methods that can be overridden. Select the one you need and click OK.

override method

The corresponding completion works when you type the override keyword.

override compleation

Scala templates

IntelliJ IDEA lets you use predefined Scala templates.

  1. In the editor start entering your code, press Ctrl+J.
    IntelliJ IDEA displays the list of available Live templates for Scala.
  2. Select the one you need and press Enter.

You can also define a new template or edit the existing one.

  1. Select Settings/Preferences | Editor | Live Templates.
  2. From options on the right, open the list of Scala templates.
    scala templates settings
  3. If you want to add a new template, click icons general add.
    If you want to edit the existing template, select the one you need and change the default definitions.

Scala postfix completion

You can transform an already typed expression to another one based on the postfix you type after a dot.
To enable/disable the postfix completion or to see a list of postfix-specific predefined templates, their descriptions and code samples, open the Postfix Completion page located in Settings/Preferences | Editor | General.
Last modified: 4 September 2018