Question

我正在实现基于订阅的IBM MQ websphere消息读取，我正在使用T，它具有基于事件的机械化。以下是我的订阅代码：

onMessageReceived是回调函数IMessage接受的数据类型。我将不得不从onMessageReceived解析邮件正文，转换为类型T并从OnMQMessageCallback

调用

    public override void Subscribe<T>(Action<T> onMessageReceived)
    {
        try
        {
            MessageListener messageListener = new MessageListener(OnMQMessageCallback);
            _consumer.MessageListener = messageListener;

            _connection.Start();
        }
        catch (Exception ex)
        {
            throw;
        }
    }

    private void OnMQMessageCallback(IMessage msg)
    {
        try
        {
            //I want to invoke onMessageReceived in this method
        }
        catch (Exception)
        {
            throw;
        }
    }

OnMQMessageCallback

从onMessageReceived()开始，我想调用从调用者传递到Subscribe()方法的button[0].addEventListener("click", function () { categorize(); addItem(); });。我无法弄明白该怎么做。

Answer 1

您可以使用anonymous delegate

实现此目的

   MessageListener messageListener = new MessageListener((m) =>         
    try
    {
        onMessageReceived();
    }
    catch (Exception)
    {

        throw;
    });`

Answer 2

如果在onMessageReceived的范围内定义了Action<T>，则无法调用Subscribe。你根本不知道T是什么。

要么你这样做，让调用者稍后处理解析：

public override void Subscribe(Action<IMessage> onMessageReceived)
{
    MessageListener messageListener = new MessageListener(onMessageReceived);
    _consumer.MessageListener = messageListener;

    _connection.Start();
}

或者你自己解析（不知道如何）并称之为：

public override void Subscribe<T>(Action<T> onMessageReceived)
{
    MessageListener messageListener = new MessageListener((m) =>         
    {
        T result = (T) m.Body; // or some other casting
        onMessageReceived(result);
    });`

    _consumer.MessageListener = messageListener;

    _connection.Start();
}

不再需要OnMQMessageCallback。

旁注：try..catch..throw没有任何意义，与完全没有try..catch相同。

如何将通用操作委托转换为具体的操作委托？

2 个答案: