MPS 2017.3 Help

Auto-Completing Code

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

Basic code completion. Completing names and keywords

Basic code completion helps you complete names of classes, methods, and keywords within the visibility scope. When you invoke code completion, MPS analyses the context and suggests the choices that are reachable from the current caret position.

Code completion covers supported and custom file types. However, MPS does not recognize the structure of custom file types and suggests completion options regardless of whether a specific type is appropriate in the current context.

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

To use basic code completion:

  1. Start typing a name.
  2. Press N/A or choose Code | Completion | Basic from the main menu.
  3. If necessary, press N/A for the second time (this action produces the same effect as pressing N/A).

Smart code completion. Completing code based on type information

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

To use smart code completion:

  1. Start typing. Press N/A.

    SmartType code completion automatically highlights the selection in the suggestions list that is most suitable for the current context.

  2. If necessary, press N/A once again.

Completing statements

Complete statements enables you to create syntactically correct code constructs. This command inserts necessary syntax elements (parentheses, braces, semicolons etc.) and gets you in position where you can start typing the next statement.

To automatically complete a statement, start typing it. The punctuation required in the current context is added and the caret moves to the next editing position.

  • Completing a method declaration: start typing a method declaration and press N/A after the opening parenthesis:

    This will create an entire construct of a method, the caret resting inside the method body:

  • Completing code constructs: start typing a code construct and press N/A:

    MPS automatically completes the construct, and the caret is placed at the next editing position:

  • : MPS automatically encapsulates a method call when you directly type a new method call next to it.

    For example, type

    and then type the method call. When println gets the focus in the suggestion list, select it with N/A:
    The resulting code will look like the following:

Hippie completion. Expanding words based on context

Hippie completion is a completion engine that analyses your text in the visible scope and draws its completion proposals from the current context. It helps you complete a word with a keyword, class name, method or variable.

To expand a string at caret to an existing word, do the following:

  1. Type the initial string and do one of the following:
    • Press N/A or choose Code | Completion | Cyclic Expand Word to search for matching words before the caret
    • Press N/A 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:
  2. Press N/A to accept the suggestion, or hold the Alt key and keep pressing Slash until the desired word is found.

Postfix code completion

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

For example, the .if postfix applied to an expression wraps it with an if statement.

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

To enable/disable the postfix completion feature or separate templates, in the Settings / Preferences Dialog dialog, go to Editor | General | Postifx completion. You can also choose which key you want to use to expand postfix templates: Tab, Space, or Enter.

Postfix completion suggestions are shown as part of the basic completion suggestions list. To see a full list of postfix completions applicable in the current context, press N/A.

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. MPS will show suggestions that include the characters you've entered in any positions.

This makes the use of wildcards unnecessary:

In case of CamelCase or snake_case names, type the initial letters only. MPS 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 N/A or double-click the desired choice to insert completion to the left from the caret.
  • Press N/A to replace the characters to the right from the caret.
  • Use N/A to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, etc.)

View reference information

  • You can use the Quick Definition View by pressing N/A when you select an entry in the suggestions list:

Sort entries in the suggestions list

You can sort the suggestions list alphabetically or by relevance. To toggle between these modes, click a icon or pi icon respectively in the lower-right corner of the list.

View code hierarchy

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

  • Press N/A to view type hierarchy.
  • Press N/A to view method hierarchy.
Last modified: 10 January 2018