useEngine function

void useEngine(
  1. WapEvaluator ev, [
  2. DataSetRegistry? registry
])

Makes ev (and registry) the engine used by setvar, expression, condition, invoke and the expand* functions.

Call it when a card's screen initializes, and again after returning from another card.

Implementation

void useEngine(WapEvaluator ev, [DataSetRegistry? registry]) {
  _currentEvaluator = ev;
  _currentRegistry = registry;
  if (registry != null) {
    ev.datasetResolver = registry.resolveDataSet;
  }
}