Extension of Scan Components: To Extend Predefined Scan States for a Custom Form

Suppose that you are creating a scan mode for a custom barcode-driven form. You have inherited the following input states from the base barcode scan class: LocationState, InventoryItemState, and LotSerialState. You need to modify these states to use them in your scan mode as follows:

• For the LocationState scan state, you want to add additional validation that is specific to this current scan mode.
• For the InventoryItemState scan state, you want to add an additional absence handler that is specific to this scan mode.
• You want the LotSerialState to be active only when it is already active and when the lot or serial number is entered on receipt.

You will implement the following ways of altering the logic of the predefined components:

• You will introduce a descendant for the LocationState class.
• You will inject the logic when InventoryItemState is created.
• You will inject the logic when LotSerialState is decorated.

To alter a scan state by introducing a descendant, do the following:

1. In the CountMode class, define the LocationState class, as follows.

   public class INScanCount : WMSBase
   {
       public sealed class CountMode : ScanMode
       {
           ...  
           public new sealed class LocationState : WMSBase.LocationState
           {
               
           }
           ...
       }
   }

   You use the same name for the descendant that is used for the predefined class. The code of this activity includes two versions of the LocationState class: the original WMSBase.LocationState class and the CountMode-related INScanCount.CountMode.LocationState class. Because the original class and the descendant have the same name, you will not need to change the CreateStates() method.

2. In the LocationState class, implement the IsStateSkippable() method so that LocationState is skipped if the location is already selected, as shown in the following code.

   public new sealed class LocationState : WMSBase.LocationState
   {
       protected override bool IsStateSkippable() => Basis.LocationID != null;
   }

   In CountMode, you do not need to ask a user for a location again if the location is already selected. Therefore, you implement the IsStateSkippable() method so that LocationState is skipped if the location is already selected.

3. In the INScanCount.cs, add the following using directive.

   using PX.Data.BQL.Fluent;

4. In the LocationState class, add the Validate() method, as shown in the following code.

   public new sealed class LocationState : WMSBase.LocationState
   {
       protected override bool IsStateSkippable() => Basis.LocationID != null;
    
       protected override Validation Validate(INLocation location)
       {
           if (Basis.HasFault(location, base.Validate, out Validation fault))
               return fault;
     
           INPIStatusLoc statusLocation =
               SelectFrom<INPIStatusLoc>.
               Where<
                   INPIStatusLoc.pIID.IsEqual<WMSScanHeader.refNbr.FromCurrent>.
                   And<
                       INPIStatusLoc.locationID.IsEqual<@P.AsInt>.
                       Or<INPIStatusLoc.locationID.IsNull>>>.
               View.ReadOnly
               .Select(Basis, location.LocationID);
    
           if (statusLocation == null)
               return Validation.Fail(Msg.NotPresent, location.LocationCD);
     
           return Validation.Ok;
       }
    
       [PXLocalizable]
       public new abstract class Msg : WMSBase.LocationState.Msg
       {
           public const string NotPresent = "The {0} location is not in the list and cannot be added.";
       }
   }

   In CountMode, you need only locations that are present in the physical inventory that the user is currently processing. Therefore, you add additional validation logic in the Validate() method. You execute the base validation first. The custom validation is performed only if the base validation is passed.

To alter a scan state by injecting the logic when the scan state is created, in the CountMode class, modify the CreateStates() method as follows.

public class INScanCount : WMSBase
{
    public sealed class CountMode : ScanMode
    {
        ...
        protected override IEnumerable<ScanState<INScanCount>> CreateStates()
        {
            yield return new RefNbrState();
            yield return new LocationState();
            yield return new InventoryItemState()
                .Intercept.HandleAbsence.ByAppend((basis, barcode) => 
                {
                    if (basis.TryProcessBy<LocationState>(barcode, 
                        StateSubstitutionRule.KeepPositiveReports | 
                        StateSubstitutionRule.KeepApplication)) 
                        return AbsenceHandling.Done; 
                    return AbsenceHandling.Skipped;                
                });
            yield return new LotSerialState();
            yield return new ConfirmState();
        } 
        ...
    }
}

To alter a scan state by injecting the logic when the scan state is decorated, in the CountMode class, add the DecorateScanState() method as follows.

public class INScanCount : WMSBase
{
    ... 
    protected override ScanState<INScanCount> DecorateScanState(
        ScanState<INScanCount> original)
    {
        var state = base.DecorateScanState(original);
  
        if (state is WMSBase.LotSerialState lotSerialState)
            InjectLotSerialDeactivationOnNonEnterableLotSerials(lotSerialState);
  
        return state;
    }
  
    protected virtual void InjectLotSerialDeactivationOnNonEnterableLotSerials(
        WMSBase.LotSerialState lotSerialState)
    {
        lotSerialState
            .Intercept.IsStateActive.ByConjoin(
                basis => basis.LotSerialTrack.IsEnterable);
    } 
    ...
}