Visitors

The visitor pattern allows operations to be applied across the entire component/module tree without modifying the visited objects. A visitor is passed to Components.Accept() or Modules.Accept() on any module, and it receives a callback for each item in the collection.

How It Works

Module.Components.Accept(MyVisitor)
  → calls MyVisitor.VisitComponent(Component1)
  → calls MyVisitor.VisitComponent(Component2)

To traverse sub-modules recursively, call Accept on Module.Modules as well, and within VisitModule() call Accept again on that module's collections.

Available Visitors

Enable / Disable

Visitor	Purpose
`EnableAllComponentsVisitor`	Calls `Enable()` on every `I_Enablable` component in the collection
`DisableAllComponentsVisitor`	Calls `Disable()` on every `I_Enablable` component
`CheckComponentsEnabledVisitor`	Returns TRUE if all components are enabled

VAR
    EnableVisitor : EnableAllComponentsVisitor;
END_VAR

Module.Components.Accept(EnableVisitor);

Reset

Visitor	Purpose
`ResetAllVisitor`	Resets both components and modules
`ResetComponentsVisitor`	Resets components only
`ResetModulesVisitor`	Resets modules only

VAR
    ResetVisitor : ResetAllVisitor;
END_VAR

Module.Components.Accept(ResetVisitor);
Module.Modules.Accept(ResetVisitor);

Stop

Visitor	Purpose
`StopAllComponentsVisitor`	Calls `Stop()` on every stoppable component

Mode & State Change

Visitor	Purpose
`ChangeModeOnAllSubModulesVisitor`	Propagates a mode change to all sub-modules
`ChangeStateOnAllSubModulesVisitor`	Propagates a state change to all sub-modules
`ChangePackMLStateOnAllSubModulesVisitor`	PackML-specific state propagation

VAR
    ModeVisitor : ChangeModeOnAllSubModulesVisitor(RequestedMode := E_Mode.Auto);
END_VAR

Machine.Modules.Accept(ModeVisitor);

Events

Visitor	Purpose
`EventReactorVisitor`	Triggers state transitions in response to active events
`EventReactorPackMLVisitor`	PackML variant of event-driven state changes
`GetActiveEventSeverityVisitor`	Collects the highest active event severity across all components

Force

Visitor	Purpose
`ForceVisitor`	Sets a force state on all forcible digital components
`ReleaseAllForceVisitor`	Releases all active forces back to `Unforced`

Safety

Visitor	Purpose
`SafetyOkVisitor`	Returns TRUE if all safety components report OK
`SetSafetySimulationVisitor`	Enables or disables simulation mode on safety components

HMI

Visitor	Purpose
`GetSystemTreeJsonHmiVisitor`	Builds a JSON representation of the component/module tree for HMI
`HmiEnableDisableAllVisitor`	Enables or disables all HMI-exposed components

Task Results

Visitor	Purpose
`GetComponentsTaskResultVisitor`	Aggregates `I_TaskResult` status across all components

Example — Collecting Component Names (from Component_TEST)

VAR
    StringCollection : StringCollection<100>;
    Visitor          : ComponentVisitor_Mockup(StringCollection);
    Component        : Component_Mockup('MySensor');
END_VAR

Component.Accept(Visitor);
// StringCollection.Entries -> 1  (visitor was called once)

// Or across a module's whole collection
Module.Components.Accept(Visitor);
// StringCollection.Entries -> number of components in module

Implementing a Custom Visitor

FUNCTION_BLOCK MyVisitor IMPLEMENTS I_ComponentVisitor
METHOD VisitComponent
VAR_INPUT
    Component : I_Component;
END_VAR
    // operate on each component
    IF Component.Name = 'TargetSensor' THEN
        // ...
    END_IF
END_METHOD