Property :: select - Create a subset from a collection
The result collection contains the instances from the collection passed in rProperty , which fulfill the selection condition, i.e. for which the evaluation of the select expression passed in vExpression returns true .
The function explicitly creates a result collection. In order to perform inline selection one may set a filter condition ( filter() ). When the calling property handle refers to a non empty collection all instances are removed before performing the operation. When the calling property handle is not opened (invalid) the function creates a temporary extend for storing the result.
The function has been called select , even though this conflicts with the use of select in OSI, since it is closer to the algebraic set terminology.
Reference to the property handle that contains the result of an operation. Note that invalid properties may cause exceptions.
Implementation details
- cProperty
- Property reference
A property handle refers to a (usually) opened property. Invalid properties may cause an exception.
- vExpression
- OSI inline expression
An inline expression can be passed as operation path, as operand (something like a + b) or as complete expression. As operand, an expression may contain any expression, which is allowed in a statement, but no semicolon must be appended at the end.
Complete expressions include expression header (optional) and may include different sections in the expression body which is enclosed in { ... }.
In contrast to class expressions, inline expressions are not defined explicitly as class expressions but passed as strings to the application at run-time.
In order to pass no expression, an empty string ( String() ) has to be passed.