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Generic <T> how cast?


Generic <T> how cast?

By : user3855409
Date : January 02 2021, 06:48 AM
will help you If you need to know about the fields or properties of the type in order to "save or update", you could use reflection. That way, the class would remain truly generic.
If within your SaveOrUpdate method you mean to write an ever-expanding switch equivalent to:
code :


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Avoiding an unchecked cast for cast to a collection of a generic interface in Java for an event publisher

Avoiding an unchecked cast for cast to a collection of a generic interface in Java for an event publisher


By : Sagasu
Date : March 29 2020, 07:55 AM
hop of those help? I'm trying to create a lightweight, thread-safe in-app publish/subscribe mechanism for an Android app that I'm building. My basic approach is to keep track of a list of IEventSubscriber for each event type T and then be able to publish events to subscribing objects by passing along a payload of type T. ,
Is the unchecked cast actually safe here?
code :
for (IEventSubscriber<T> subscriber: existingSubscribers) {
List<?> list = ...
for (Object item : list) {
    IEventSubscriber<T> subscriber = (IEventSubscriber<T>) item;
}
class MyEventSubscriber<T> implements IEventSubscriber<T> { ... }
new MyEventSubscriber<String>.getClass() == new MyEventSubscriber<Integer>.getClass()
class SubscriberList<E> extends CopyOnWriteArrayList<E> {
    final Class<E> eventClass;

    public void trigger(Object event) {
        E event = eventClass.cast(event);
        for (IEventSubscriber<E> subscriber : this) {
            subscriber.trigger(event);
        }
    }
}
SubscriberList<?> subscribers = (SubscriberList<?>) subscriptions.get(eventClass);
subscribers.trigger(message);
Generic covariant cast or cast to real type

Generic covariant cast or cast to real type


By : fabrizio fonte
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Trying to build a CQRS solution, I have the following code trying to find a Handler and then invoke a Handle() method. , After playing around I found out some solutions:
code :
dynamic handler = container.Resolve(handlerType);
handler.Handle(command as dynamic);
public void SendCommand(Command command)
{
    Invoke(command as dynamic);
}

private void Invoke<T>(T command) where T : Command
{
    var handler = container.Resolve<IHandleCommand<T>>();
    handler.Handle(command);
}
private void Invoke<T>(T command) where T : Command
{
    Type handlerType = CommandToHandlerType(command);
    var handler = (IHandleCommand<T>)container.Resolve(handlerType);
    handler.Handle(command);
}
Cast<int>.Cast<int?> applied on generic enum collection results in invalid cast exception

Cast<int>.Cast<int?> applied on generic enum collection results in invalid cast exception


By : Pedro Cabo Calvet
Date : March 29 2020, 07:55 AM
I wish this helpful for you Ok I have come to find out the cause, which is still strange. I should have checked up Cast implementation myself first of all!
This is how Cast is implemented:
code :
public static IEnumerable<TResult> Cast<TResult>(this IEnumerable source)
{
    IEnumerable<TResult> enumerable = source as IEnumerable<TResult>;
    if (enumerable != null)
    {
        return enumerable; // this is the culprit..
    }
    if (source == null)
    {
        throw Error.ArgumentNull("source");
    }
    return Enumerable.CastIterator<TResult>(source);
}

private static IEnumerable<TResult> CastIterator<TResult>(IEnumerable source)
{
    foreach (object current in source)
    {
        yield return (TResult)((object)current);
    }
    yield break;
}
new[] { Gender.Male }.Cast<int>()
Error trying to cast to generic type: redundant cast

Error trying to cast to generic type: redundant cast


By : Tan Kiat Yao
Date : March 29 2020, 07:55 AM
I wish this helpful for you There's one glaring thing in your implementation that is incorrect, which other's have pointed out but haven't addressed satisfactorily. If you intend to instantiate TListVM, then you need to change two very important parts. First the new code listing:
code :
public TListVM MakeListVM<TListVM>()
    where TListVM : AnyListVM, new()
{
    TListVM listVM = new TListVM();

    EventListVM evtList = listVM as EventListVM;
    if (evtList != null)
    {
        // set evtList properties.  You can't change
        // the instantiation method.
    }

    // repeat for other constructs.

    return listVM;
}
public AnyListVM MakeListVM<TListVM>()
    where TListVM : AnyListVM
{
    return MakeListVM(typeof(TListVM)) as TListVM;
}

private AnyListVM MakeListVM(Type listVM)
{
    AnyListVM listVM;
    switch(listVM.ToString())
    {
        case nameof(EventListVM):
            listVM = new EventListVM();
            // some more init stuff
            break;

        // some more similar cases

        default:
            throw new NotImplementedException();
    }
    return listVM;
}
Generic method performs implicit cast while non-generic method needs explicit cast

Generic method performs implicit cast while non-generic method needs explicit cast


By : Ravinder
Date : March 29 2020, 07:55 AM
wish helps you There are 2 things happening. First of all if you look at the javadoc for getClass it will say:
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