CLion 2024.2 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 names, types, and keywords within the visibility scope.

When you invoke code completion, CLion analyzes 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

  • By default, CLion displays the code completion popup automatically as you type. Alternatively, you can press Ctrl+Space or select Code | Code Completion | Basic from the main menu.

    Basis completion popup

Type-matching completion

Smart type-matching code completion filters the suggestion list and shows only the types applicable to the current context.

Invoke type-matching completion

  • To invoke type-matching completion, start typing and press Ctrl+Shift+Space or select Code | Code Completion | Type-Matching from the main menu.

    Smart type completion

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 | Code Completion | Cyclic Expand Word to search for matching words before the caret.

    • Press Alt+Shift+/ or choose Code | 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.

    Expand word

  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.

In CLion, postfix code completion is available for C/C++, Python, Rust, JavaScript, TypeScript, and SQL.

For C++, postfix completion can be especially useful for the cases of wrapping with a C++-style cast, make_shared/make_unique, various loops, and begin/end idioms.

Enable and configure postfix completion

  • In the Settings dialog (Ctrl+Alt+S), open Editor | General | Postfix Completion and select the Enable postfix completion checkbox.

  • Select Tab, Space, or Enter to be used for expanding postfix templates.

  • Enable/disable a particular postfix template for the selected language.

Postfix completion settings

Transform a statement with a postfix

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

    void myfunc (int arg) { arg.if }

    The initial expression gets wrapped with an if statement:

    void myfunc (int arg) { if (arg) }

Postfix completion options are shown as part of the basic completion suggestion list:

Postfix templates in suggestion list

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.

Edit a postfix template name

  1. Press Ctrl+Alt+S to open settings and then select Editor | General | Postfix Completion.

  2. Double-click a template name in the tree and edit it as required:

    Editing a template name

Create custom postfix templates (JavaScript, TypeScript, SQL, Rust)

  1. Press Ctrl+Alt+S to open settings and then select Editor | General | Postfix Completion.

  2. Click the Add button (the Add button) on the toolbar.

  3. In the Create New Template dialog that opens, specify Key, a combination of symbols after the dot that will invoke the template.

  4. 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.

Machine-learning-assisted completion ranking

CLion allows you to prioritize completion suggestions based on choices that other users made in similar situations.

The ML completion mechanism doesn't add any new elements but orders the elements retrieved from code. Data is not exposed anywhere; it is collected locally.

Enable ML completion

  1. Press Ctrl+Alt+S to open settings and select Editor | General | Code Completion.

  2. Under Machine Learning Completion Ranking, enable the Sort completion suggestions based on machine learning option, and select the languages for which you want to use ML completion.

    ML-assisted completion settings

Enable relevance markers

  1. Press Ctrl+Alt+S to open settings and select Editor | General | Code Completion.

  2. Enable the following options:

    ML completion markers settings

    • Mark position changes in the completion popup: use the Machine Learning ranking Up and Machine Learning ranking Down icons to indicate whether the relevance of a suggestion is increasing or decreasing and therefore the suggestion has moved up or down the suggestion list.

    • Mark the most relevant item in the completion popup: use the ML relevant proposal icon to indicate the most suitable suggestion on the list.

    The suggestion list will look as follows with the icons marking reordered and the most relevant items.

    ML-assisted completion with markers

Code completion settings

To configure code completion options, go to the Editor | General | Code Completion page of settings  Ctrl+Alt+S.

You can choose the following settings:

Item

Description

Match case

Select if you want the letter case to be taken into account for completion suggestions. Choose whether you want to match the case for the first letter or for all letters.

Automatically insert single suggestions for

Automatically complete code if there's just one suggestion for basic and smart type-matching completion.

Sort suggestions alphabetically

Select if you want to sort items in the suggestion list in the alphabetical order instead of sorting them by relevance.

You can change this behavior at any time by clicking in the suggestion list and toggling the Sort by Name option.

Show suggestions as you type

Select if you want the suggestion list to be invoked automatically, without having to call completion explicitly. This option is enabled by default.

Show the documentation popup in

Select to automatically show a popup for each item in the suggestion list with the documentation for the class, method, or field currently highlighted in the lookup list.

In the field to the right, specify the delay (in milliseconds), after which the popup should appear.

Insert parentheses automatically when applicable

If this option is enabled, CLion automatically inserts a pair of opening and closing parentheses when you complete a function/method.

Clear the checkbox to suppress inserting parentheses automatically.

If you use an opening parentheses ( instead of Enter to apply the selected item from a completion list, parentheses will be inserted automatically no matter whether the option is turned on or off.

To use an opening parentheses ( instead of Enter to apply the selected item from a completion list, open the Settings dialog (Ctrl+Alt+S) , go to Editor | General | Code Completion, and select the Insert selected suggestion by pressing space, dot, or other context-dependent keys checkbox.

For more information, refer to Use specific keys to insert suggestions.

Show import items in basic completion

When a symbol that you want to use is not imported in the current file with the corresponding #include, but it is defined in the standard libraries or elsewhere in your solution, you can press Ctrl+Alt+Space to quickly find this symbol in completion suggestions.

You can use this option to include import symbol suggestions into the suggestion lists of automatic and basic completion.

Behavior of import items

Configure the import completion behavior to always insert an include directive or show a menu with an option to add a forward declaration.

Show free functions in members completion

One common C++ coding practice is to prefer non-member non-friend functions to member functions. This is a great way to increase encapsulation and keep class interfaces as minimal as possible. When you type a dot . or an arrow -> after an expression, free functions that accept the expression as the first parameter will be suggested in the completion list after member functions.

Clear this checkbox if you do not want to have free functions in the completion suggestions.

Machine Learning-Assisted Completion

Enable Full line suggestions

Enable Full Line code completion to get suggestions for an entire line of code. Select the language you use in your project; the suggestions will be in gray italics.

Sort completion suggestions based on machine learning

Select this option if you want to use machine learning models to rank the most suitable items higher in the suggestion list. Select the languages for which you want to enable suggestions based on Machine Learning.

Mark position changes in the completion popup

Use the Machine Learning ranking Up and Machine Learning ranking Down icons to indicate whether the relevance of a suggestion is increasing or decreasing and therefore the suggestion has moved up or down the suggestion list.

Mark the most relevant item in the completion popup

Use the ML relevant proposal icon to indicate the most suitable suggestion on the list.

JavaScript

Only type-based completion

By default, CLion suggests completion for symbols regardless of their types. With this approach, in complicated cases the list shows multiple completion variants.

To make completion more precise, select this option. The completion list will strongly depend on the CLion inference. As a result, the list may remain empty in case of poor inference.

Suggest items with optional chaining for nullable types

By default, CLion suggests completion for symbols with the optional chaining operator (?). Clear this checkbox to suppress this behavior.

Expand method bodies in completion for overrides

By default, when you want to override a method from the parent class or interface and select this method from the list of completion suggestions, CLion automatically adds parameters, generates a super() call, and adds the type information, if possible.

Clear this checkbox to suppress automatic generation of method bodies for overrides during completion.

Completion of names

  • Suggest variable and parameter names: By default, the checkbox is cleared. When it is selected, CLion suggests names for new class fields, variables, and parameters during their declaration. These suggestions are based on the names of classes, types, and interfaces that are defined in your project, in the libraries you are using, and in standard APIs.

  • Suggest names for class fields

    The option is turned off by default.

  • Add type annotations for suggested parameter names: Select this checkbox to supply each completion suggestion with information on its type.

    The checkbox is available only when the Suggest variable and parameter names checkbox is selected.

Parameter Info

Show the parameter info popup (in ms)

Select this checkbox to have CLion automatically show a popup with all available method signatures when an opening bracket is typed in the editor, or a method is selected from the suggestion list.

In the text field to the right, specify the delay (in milliseconds) after when the popup window should appear.

If this checkbox is not selected, use Ctrl+P to show parameter info.

Show full method signatures

If this checkbox is selected, the parameter info displays full signatures, including method name and returned type.

SQL

Use aliases in completion for JOIN

Creates aliases for tables in the JOIN statement.

Use aliases in completion for JOIN

Invert order of operands in auto-generated ON clause

Switches operands in the ON clause. When the checkbox is cleared, the FROM table comes the first in the JOIN condition.

Invert order of operands in auto-generated ON clause

Automatically add aliases when completing table names

Creates an alias for a table name.

Automatically add aliases when completing table names

Suggest alias names in completion after table names

Suggests an alias for a table name when you use code completion (Ctrl+Space).

Suggest alias names in completion after table names

Custom aliases (table)

You can add a table name and the alias that you want to use for this table. To add the table-alias pair, click the Add alias button (the Add alias button).

Completion tips and tricks

Open completion settings from the completion popup

You can quickly access code completion settings right from the completion popup.

  • Click the icon in the completion popup and select Code Completion Settings.

    Opening completion settings

After that, the Editor | General | Code Completion page of settings  Ctrl+Alt+S opens.

Narrow down the suggestion list

  • You can narrow down the suggestion 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 have 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 and custom characters to accept the selected completion suggestion. To enable these features, go to the Editor | General | Code Completion page of settings  Ctrl+Alt+S and do the following:

    1. To use specific keys, select the Insert the selected suggestion by pressing space, dot, or other context-dependent keys checkbox. These keys depend on the language, your context, and so on.

    2. To also use custom characters, enter the characters into the Additional characters to accept the completion field.

View reference

  • You can use the by pressing Ctrl+Shift+I when you select an entry in the suggestion list:

    Quick Definition for an item in the suggestion list

  • You can use the Quick Documentation view by pressing Ctrl+Q when you select an entry in the suggestion list:

    Quick documentation for an item in the suggestion list

View code hierarchy

You can view code hierarchies when you've selected an entry from the suggestion 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.

  • 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 with the symbols that you want to appear in completion is excluded from indexing.

  • Code completion popup might not appear automatically if it takes too long to gather the completion options. For example, if the computer is busy with another task. In this case, you may still activate the completion popup manually via Ctrl+Space.

Last modified: 16 October 2024
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