Package net.sf.saxon.expr

Class CallableDelegate

java.lang.Object
net.sf.saxon.expr.CallableDelegate
All Implemented Interfaces:
Callable
public class CallableDelegate extends Object implements Callable
An implementation of Callable that allows the logic to be supplied as a lambda expression.

On Java, it's possible to assign a lambda expression directly to a Callable. But on C#, a Callable isn't a delegate, so lambda expressions can't be used directly; instead, this class is provided as a proxy.

  • Constructor Details

    • CallableDelegate

      public CallableDelegate(CallableDelegate.Lambda expression)
      Construct a Callable by supplying an implementation in the form of a lambda expression
      Parameters:
      expression - a lambda expression (typically) that is invoked to evaluate the Callable

  • Method Details

    • call

      public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException
      Description copied from interface: Callable
      Call the Callable.
      Specified by:
      call in interface Callable
      Parameters:
      context - the dynamic evaluation context
      arguments - the values of the arguments, supplied as Sequences.

      Generally it is advisable, if calling iterate() to process a supplied sequence, to call it only once; if the value is required more than once, it should first be converted to a GroundedValue by calling the utility method SequenceTool.toGroundedValue().

      If the expected value is a single item, the item should be obtained by calling Sequence.head(): it cannot be assumed that the item will be passed as an instance of Item or AtomicValue.

      It is the caller's responsibility to perform any type conversions required to convert arguments to the type expected by the callee. An exception is where this Callable is explicitly an argument-converting wrapper around the original Callable.

      Returns:
      the result of the evaluation, in the form of a Sequence. It is the responsibility of the callee to ensure that the type of result conforms to the expected result type.
      Throws:
      XPathException - if a dynamic error occurs during the evaluation of the expression