/// <summary>
/// 使用简单工厂方法创建一个用于执行 <paramref name="asyncAction"/> 异步任务的重新进入状态机。
/// </summary>
/// <param name="asyncAction">要被异步重新进入状态机调用的具体异步任务。</param>
/// <param name="reentrancyPolicy">重新进入策略。</param>
public static ReentrancyStateMachine FromPolicy(Func <object, Task> asyncAction,
ReentrancyPolicy reentrancyPolicy)
{
ReentrancyStateMachine stateMachine;
switch (reentrancyPolicy)
{
case ReentrancyPolicy.Disable:
stateMachine = new DisableReentrancyStateMachine();
break;
case ReentrancyPolicy.RunImmediately:
stateMachine = new RunImmediatelyReentrancyStateMachine();
break;
//case ReentrancyPolicy.CancelAndRestart:
// stateMachine = new CancelAndRestartReentrancyStateMachine();
// break;
case ReentrancyPolicy.Queue:
stateMachine = new QueueReentrancyStateMachine();
break;
case ReentrancyPolicy.KeepLast:
stateMachine = new KeepLastReentrancyStateMachine();
break;
default:
throw new ArgumentOutOfRangeException(nameof(reentrancyPolicy), reentrancyPolicy, null);
}
stateMachine.AsyncAction = asyncAction ?? throw new ArgumentNullException(nameof(asyncAction));
return(stateMachine);
}
/// <summary>
/// 创建一个没有异步控制流的，带一个或多个泛型参数的异步命令。同时可以指定此异步的重新进入策略。
/// </summary>
/// <param name="asyncAction">异步任务。</param>
/// <param name="reentrancyPolicy">异步任务的重新进入策略。</param>
public AsyncCommand([NotNull] Func<T, Task> asyncAction,
ReentrancyPolicy reentrancyPolicy = default)
: base(reentrancyPolicy)
{
if (asyncAction == null)
throw new ArgumentNullException(nameof(asyncAction));
_asyncAction = (context, t) => asyncAction(t);
}
/// <summary>
/// 当派生类使用此构造函数构造父类时，指定异步任务的重新进入策略。
/// 派生类需要自己处理异步任务本身，需要重写 <see cref="ExecuteAsyncCore"/> 方法来执行异步任务。
/// </summary>
/// <param name="reentrancyPolicy">异步任务的重新进入策略。</param>
protected AsyncCommandBase(ReentrancyPolicy reentrancyPolicy = default)
{
if (!Enum.IsDefined(typeof(ReentrancyPolicy), reentrancyPolicy))
{
throw new InvalidEnumArgumentException(
nameof(reentrancyPolicy), (int)reentrancyPolicy, typeof(ReentrancyPolicy));
}
_reentrancyInvoker = ReentrancyStateMachine.FromPolicy(ExecuteWithStatesAsync, reentrancyPolicy);
ReentrancyPolicy = reentrancyPolicy;
}
/// <summary>
/// 创建用于执行指定异步任务 <paramref name="asyncAction"/> 的 <see cref="AsyncCommand"/>。
/// 可选的，可以指定异步任务的重新进入策略。
/// </summary>
/// <param name="asyncAction">异步命令中执行的异步任务。</param>
/// <param name="reentrancyPolicy">异步任务的重新进入策略。</param>
public AsyncCommand([NotNull] Func <AsyncExecutingContext, Task> asyncAction,
ReentrancyPolicy reentrancyPolicy = default)
: base(reentrancyPolicy)
{
_asyncAction = asyncAction ?? throw new ArgumentNullException(nameof(asyncAction));
}
