/// <summary>
/// The shadow is to be created
/// </summary>
/// <param name="context"></param>
/// <param name="viewElement"></param>
/// <returns></returns>
/// <remarks>
/// It is assumed that this is invoked whilst operating under a transaction.
/// </remarks>
public IShadow CreateShadow(IShadowContext context, IPrimitive viewElement)
{
var shadow = Create((TContext)context, (TElement)viewElement);
Transaction.Current.Add(() => OnShadowCreated((TContext)context, (IShadow <TItem>)shadow, (TElement)viewElement));
return(shadow);
}
/// <summary>
/// The shadow has been removed.
/// </summary>
/// <param name="context"></param>
/// <param name="shadow"></param>
/// <param name="current"></param>
public void RemoveShadow(IShadowContext context, IShadow shadow, IPrimitive current)
{
Remove((TContext)context, (IShadow <TItem>)shadow, (TElement)current);
OnShadowDestroyed((TContext)context, (IShadow <TItem>)shadow, (TElement)current);
// and here, we dispose of the shadow
Transaction.Current.Add(shadow.Dispose);
}
/// <summary>
/// Update a shadow given current and next values.
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="context"></param>
/// <param name="current"></param>
/// <param name="next"></param>
/// <param name="shadow"></param>
/// <param name="added"></param>
/// <param name="removed"></param>
public static void Update <TItem>(IShadowContext context, IPrimitive current,
IPrimitive next,
IShadow <TItem> shadow,
Action <IShadow <TItem> > added = default,
Action <IShadow <TItem> > removed = default)
{
// current == null and next != null implies -> new
// current != null && next != null implies -> update/change
// current != null && next == null, implies -> remove
try
{
// now, we do have a problem in that the shadow may not exist...//
// if so then its a create
if (shadow != null)
{
// the shadow could well change...
// in this case, we need to ...
var sameElementType = current.AreSameType(next);
if (!sameElementType)
{
if (current != null)
{
// this isn't right, since the layout hasn't been retained
context.MapperFactory.Remove(context, shadow, current);
// we could want to 'drop' the content view here, how would we do that ?
removed?.Invoke(shadow);
shadow = default;
}
}
else
{
context.MapperFactory.Update(context, shadow, current, next);
}
}
if (shadow == null)
{
var baseShadow = context.MapperFactory.Create(context, next);
shadow = (IShadow <TItem>)baseShadow;
added?.Invoke(shadow);
}
}
catch (Exception exception)
{
Logging.Instance.LogError(exception, "Shadow:Update Current:{current} Next:{next} ShadowType:{shadowType}", current, next, shadow?.GetType().FriendlyName());
throw;
}
}
/// <summary>
/// Create an <see cref="IShadow"/> instance for a specified <see cref="IElement"/>
/// </summary>
/// <param name="context"></param>
/// <param name="element"></param>
/// <param name="update"></param>
/// <returns></returns>
/// <remarks>
/// The creation of the shadow is transactional, the actual Item within the Shadow isn't assigned until the transactions are committed.
/// The option to not perform an update is primarily for those situations in which a placeholder view/shadow is being created
/// and it will be bound at a slightly later date.</remarks>
public IShadow Create(IShadowContext context, IPrimitive element, bool update = true)
{
var mapper = GetShadowMapper(element);
var shadow = mapper.CreateShadow(context, element);
if (update)
{
mapper.UpdateShadow(context, shadow, null, element);
}
return(shadow);
}
/// <summary>
/// Simple extension to assign / update a <see cref="IShadow{TItem}"/> when it has content within it, with
/// updates being automatically wrapped in a <see cref="Transaction"/>
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="context"></param>
/// <param name="shadow"></param>
/// <param name="current"></param>
/// <param name="next"></param>
/// <param name="set"></param>
/// <param name="clear"></param>
public static void UpdateContent <TItem>(this IShadow shadow, IShadowContext context, IPrimitive current,
IPrimitive next,
Action <IShadow <TItem> > set,
Action <IShadow <TItem> > clear)
{
var content = shadow.Get <IShadow <TItem> >(ContentKey);
Shadow.Update(context, current, next, content, (s) =>
{
Transaction.Current.Add(() =>
{
shadow.Set <IShadow <TItem> >(ContentKey, s);
set(s);
});
}, (s) =>
{
Transaction.Current.Add(() =>
{
shadow.State.Delete <IShadow <TItem> >(ContentKey);
clear(s);
});
});
}
private static IDataConnector <IPrimitive> ConnectorFactory(IShadowContext context, IShadow <Xamarin.Forms.StackLayout> shadow)
{
return(new ShadowGroupConnector <Xamarin.Forms.View>(context, new StackLayoutConnection(shadow)));
}
/// <summary>
/// A shadow instance is being removed, perform any logic prior to removal.
/// </summary>
/// <param name="context"></param>
/// <param name="shadow"></param>
/// <param name="current"></param>
public void Remove(IShadowContext context, IShadow shadow, IPrimitive current)
{
var viewHandler = GetShadowMapper(current);
viewHandler.RemoveShadow(context, shadow, current);
}
/// <summary>
/// Update an existing <see cref="IShadow"/> from its current state to a new state.
/// </summary>
/// <param name="context"></param>
/// <param name="shadow"></param>
/// <param name="current"></param>
/// <param name="next"></param>
public void Update(IShadowContext context, IShadow shadow, IPrimitive current, IPrimitive next)
{
var viewHandler = GetShadowMapper(current ?? next);
viewHandler.UpdateShadow(context, shadow, current, next);
}
/// <summary>
/// The shadow is potentially going to be updated
/// </summary>
/// <param name="context"></param>
/// <param name="shadow"></param>
/// <param name="current"></param>
/// <param name="next"></param>
public void UpdateShadow(IShadowContext context, IShadow shadow, IPrimitive current,
IPrimitive next)
{
UpdateImplementation((TContext)context, (IShadow <TItem>)shadow, (TElement)current, (TElement)next);
}
private static IDataConnector <IPrimitive> ConnectorFactory(IShadowContext context, IShadow <Xamarin.Forms.CollectionView> shadow)
{
return(new CollectionViewConnector(shadow));
}
