CLion 2019.3 Help

Code completion

This section covers various techniques of context-aware code completion that allow you to speed up your coding process.

Basic completion

Basic code completion helps you complete the names of classes, methods, and keywords within the visibility scope. When you invoke code completion, CLion analyses the context and suggests the choices that are reachable from the current caret position (suggestions also include Live templates).

If basic code completion is applied to a part of a field, parameter, or variable declaration, CLion suggests a list of possible names depending on the item type.

Invoke basic completion

  1. Start typing a name.

    Basis completion popup

  2. Press Ctrl+Space or choose Code | Completion | Basic from the main menu.

  3. If necessary, press Ctrl+Space for the second time (or press Ctrl+Alt+Space).

Smart completion

Smart code completion filters the suggestions list and shows only the types applicable to the current context.

Invoke smart completion

  1. Start typing.

  2. Press Ctrl+Shift+Space or choose Code | Completion | SmartType from the main menu.

    Smart type completion

  3. If necessary, press Ctrl+Shift+Space once again.

Statement completion

You can create syntactically correct code constructs by using statement completion. It inserts the necessary syntax elements (parentheses, braces, and semicolons) and gets you in a position where you can start typing the next statement. To invoke statement completion, start typing a code construct and press Ctrl+Shift+Enter.

Complete Statement works with the following language constructs:

  • Type and type members: classes, namespaces, and enums.

  • Statements: if/else, while, do, for, switch/case, try/catch.

Complete a function declaration

  • Start typing a function declaration and press Ctrl+Shift+Enter after the opening parenthesis.

    Before Complete Statement

    After Complete Statement

    void myFunc(/*caret*/
    void myFunc();/*caret*/

Complete a code construct

  • Start typing a code construct and press Ctrl+Shift+Enter.

    CLion automatically completes the construct and adds the required punctuation. The caret is placed at the next editing position.

    Use case

    Before Complete Statement

    After Complete Statement

    Class declaration

    class NewClass /*caret*/
    class NewClass { /*caret*/ };

    switch clause

    switch/*caret*/
    switch (/*caret*/) {}
    switch (i /*caret*/) {}
    switch (i) { /*caret*/ }

    while statement

    while/*caret*/
    while (/*caret*/) {}
    while (n > 0/*caret*/) {}
    while (n > 0) { /*caret*/ }

    if statement

    if /*caret*/
    if (/*caret*/) {}
    if (n > 0/*caret*/) {}
    if (n > 0) { /*caret*/ }

    for statement

    for /*caret*/
    for (/*caret*/) {}
    for (int i = 0; i < 10; ++i/*caret*/) {}
    for (int i = 0; < 10; ++i) { /*caret*/ }

    Try-catch statement

    try /*caret*/
    try { /*caret*/ }
    catch /*caret*/
    catch (/*caret*/) { }
    catch (const std::exception/*caret*/) {}
    catch (const std::exception) { /*caret*/ }

Hippie completion

Hippie completion is a completion engine that analyses your text in the visible scope and generates suggestions from the current context. It helps you complete any word from any of the currently opened files.

Expand a string at caret to an existing word

  1. Type the initial string and do one of the following:

    • Press Alt+/ or choose Code | Completion | Cyclic Expand Word to search for matching words before the caret.

    • Press Shift+Alt+/ or choose Code | Completion | Cyclic Expand Word (Backward) to search for matching words after the caret and in other open files.

    The first suggested value appears, and the prototype is highlighted in the source code.

    Hippie completion
  2. Accept the suggestion, or hold the Alt key and keep pressing / until the desired word is found.

Postfix code completion

Postfix code completion helps you reduce backward caret jumps as you write code. You can transform an already-typed expression to a different one based on a postfix you type after the dot, the type of expression, and its context.

  • To view a full list of available postfix templates, in the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Postfix Completion.

  • Select Tab, Space, or Enter to expand postfix templates.

Transform a statement with a postfix

  • Type an expression and then type a postfix after a dot, for example, .if:

    function m(arg) { arg.if }

    The initial expression gets wrapped with an if statement:

    function m(arg) { if (arg) { } }

To disable certain postfix completion templates, in the Settings/Preferences dialog Ctrl+Alt+S select Editor | General | Postfix Completion.

You can selectTab, Space, or Enter to expand postfix templates.

You can edit the predefined postfix templates, for example, to replace a long key with a shorter one, or to expand the list of applicable expression types.

Create custom postfix templates

  1. In the Settings/Preferences dialog Ctrl+Alt+S, go to Editor | General | Postfix Completion.

  2. Click the Add button on the toolbar.

  3. Specify the Key, that is the combination of symbols that will invoke the template, select which expression types the new template will be applicable to, and type the target expression in the following format: $EXPR$ <target_expression>, for example, $EXPR$ =!null.

Completion of tags and attributes

CLion automatically completes names and values of tags and attributes in many file types:

Completion of tags and attribute names is based on the DTD or Schema the file is associated with. If there is no schema association, CLion will use the file content (tag and attribute names and their values) to complete your input.

Complete tag names

  1. Press < and start typing the tag name. CLion displays the list of tag names appropriate in the current context.

    Tags completion
    Use the Up and Down buttons to scroll through the list.

  2. Press Enter to accept a selection from the list. If your file is associated with a schema or a DTD, CLion automatically inserts the mandatory attributes according to it.

Import a taglib declaration

If you need to use tags declared in a tag library, you need to import this taglib before any custom tag from it can be used.

  1. Start typing a taglib prefix and press Alt+Insert.

  2. Select a taglib from the list and press Enter.

    Import taglib declaration

    CLion imports the selected taglib and adds the import statement automatically.

Insert a tag declared in a taglib

  1. Start typing a tag and press Ctrl+Alt+Space.

  2. Select a tag from the list. The uri of the taglib it belongs to is displayed in brackets.

    Tag completion: before

  3. Select the desired taglib and press Enter. CLion adds the declaration of the selected taglib:

    Tag completion: after

Configure code completion settings

Configure completion options

  1. In the Settings/Preferences dialog Ctrl+Alt+S, select Editor | General | Code Completion.

    • To automatically display the suggestions list, select the Show suggestions as you type checkbox. If the checkbox is cleared, you have to call code completion explicitly by pressing Ctrl+Space for basic completion or Ctrl+Shift+Space for smart completion.

      You can also choose to automatically insert suggestions when there's just one option: select the completion type under Automatically insert single suggestions for.

    • To sort suggestions in the alphabetical order, instead of sorting them by relevance, select the Sort suggestions alphabetically checkbox.

      You can also toggle these modes by clicking the Sort Alphabetically button or the Sort by Relevance button respectively in the lower-right corner of the suggestions list.

    • If you want the word case to be taken into account when suggesting completion options, select Match case and choose whether you want to match case for first letters only, or for all letters.

    • If you want the documentation popup to be displayed automatically for each item in the suggestions list as you scroll it, select the Show documentation popup in option. In the field to the right, specify the delay (in milliseconds), after which the popup should appear.

Completion tips and tricks

Narrow down the suggestions list

You can narrow down the suggestions list by typing any part of a word (even characters from somewhere in the middle) or invoking code completion after a dot separator. CLion will show suggestions that include the characters you've entered in any positions.

This makes the use of wildcards unnecessary:

Code completion wild cards

In case of CamelCase or snake_case names, type the initial letters only. CLion automatically recognizes and matches the initial letters.

Accept a suggestion

You can accept a suggestion from the list in one of the following ways:

  • Press Enter or double-click a list item to insert it to the left of the caret.

  • Press Tab to replace the characters to the right from the caret.

  • Use Ctrl+Shift+Enter to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, and so on).

You can also use specific keys to insert the selected completion suggestion: in the Settings/Preferences dialog Ctrl+Alt+S choose Editor | General | Code Completion and select the Insert selected suggestion by pressing space, dot, or other context-dependent keys option. These keys depend on the language, your context, and so on.

View reference

  • You can use the Quick Definition View by pressing Ctrl+Shift+I when you select an entry in the suggestions list:

    cl_suggestion_list_defs

  • You can use the Quick Information View by pressing Ctrl+Q when you select an entry in the suggestions list:

    cl_suggestion_list_docs

View code hierarchy

You can view code hierarchies when you've selected an entry from the suggestions list:

  • Ctrl+H - view type hierarchy

  • Ctrl+Alt+H - view call hierarchy.

Troubleshooting

If code completion doesn't work, this may be due to one of the following reasons:

  • The Power Save Mode is on (File | Power Save Mode). Turning it on minimizes power consumption of your laptop by eliminating the background operations, including error highlighting, on-the-fly inspections, and code completion.

  • An SDK is not configured for your project.

  • Your file doesn't reside in a content root, so it doesn't get the required class definitions and resources needed for code completion.

  • A file containing classes and functions that you want to appear in completion suggestions list is marked as a plain text file.

  • External libraries that contain functions that you want to appear in the completion suggestions list are not added as dependencies or global libraries.

Last modified: 6 December 2019