h2. Content Assist Support

bq.. 
The Content Assist facilities described here are used by the Interactive OCL Console. They are not used by the new Xtext-based Editors or the Interactive Xtext OCL Console.
p. 
The "@OCLHelper@":http://download.eclipse.org/ocl/javadoc/6.3.0/org/eclipse/ocl/helper/OCLHelper.html API provides support for content-assist in rich editors, by parsing partial OCL
expressions and supplying completion suggestions. The
@List<Choice> getSyntaxHelp(ConstraintKind, String)@ operation
returns a list of suggestions for the next token to follow the end of the
expression fragment.

!{width:100%}images/5140-contentassist.png(OCL Content Assist API)!

The "@Choice@":http://download.eclipse.org/ocl/javadoc/6.3.0/org/eclipse/ocl/helper/Choice.html objects returned by the helper include some convenient text strings (name and
description) to formulate basic JFace content-assist proposals.  Each choice
also carries a reference to the element that it represents, the kind of element
indicated by the @ChoiceKind@ enumeration, for a more
sophisticated content assist that might inlude context information, documentation,
etc. as in Eclipse JDT.  The list of choices depends in part on the kind of
constraint expression that is to be completed, as for example, the
@oclIsNew()@ operation is only permitted in operation
post-conditions.

bc.. 
helper.setContext(EXTLibraryPackage.Literals.BOOK);

List<Choice> choices = helper.getSyntaxHelp(ConstraintKind.INVARIANT,
    "Book.allInstances()->collect(author)->");

for (Choice next : choices) {
    switch (next.getKind()) {
    case OPERATION:
    case SIGNAL:
        // the description is already complete
        System.out.println(next.getDescription());
    case PROPERTY:
    case ENUMERATION_LITERAL:
    case VARIABLE:
        System.out.println(next.getName() + " : " + next.getDescription();
        break;
    default:
        System.out.println(next.getName());
        break;
    }
}
p. 

h3. Syntax Completion Choices

The computation of @Choice@ s is supported for the
following tokens, which may be used by a client as auto-assist triggers:

table{border:1px solid black}. 
|_. Token|_. Completion choices|
|@.@|Features applicable to the type of the expression to the left of the dot, or its element type if it is a collection. association classes (in the UML environment only)|
|@->@|Collection operations and iterators|
|@::@|Packages, types, enumeration literals, and states (in the UML environment only)|
|@^@|/2. Operations and signals (in the UML environment only)|
|@^^@| |
| |In other situations, the choices the current context variables and implicit references to features of the @self@ variable.  For example, if the input is something like @""@ or @"self.isOrdered and "@|
*Content-assist triggers*

The completion of partially specified identifiers is also supported, by
backtracking to look for one of these triggering tokens.  This supports
interactively narrowing the choices while the content-assist window is active.

bc.. 
choices = helper.getSyntaxHelp(ConstraintKind.POSTCONDITION,
    "self.author.oclIs");
p. 

