使用异步和同步调用收集结果

Question

我有以下代码。它基本上扩展了 EventEmitter，因此它实际上收集了结果，而不是发出事件并忘记它。

我写它是为了回答这个问题：EventEmitter implementation that allows you to get the listeners' results?

此代码的问题在于它假定每个 侦听器都是异步的。如果其中之一是异步的，那么 async.series 就会失败。

我的想法是用一个函数包装监听器，检查它的最后一个参数是否是一个函数。它不是，它应该用一个与异步调用类似的函数来包装它。但是，我在这方面做得很糟糕。

帮助？

var events = require('events');
var util = require('util');
var async = require('async');

// Create the enhanced EventEmitter
function AsyncEvents() {
    events.EventEmitter.call(this);
}
util.inherits(AsyncEvents, events.EventEmitter);

// Just a stub
AsyncEvents.prototype.onAsync = function( event, listener ){
  return this.on( event, listener );
}

// Async emit
AsyncEvents.prototype.emitAsync = function( ){

  var event,
  module,
  results = [],
  functionList = [],
  args,
  callback,
  eventArguments;

  // Turn `arguments` into a proper array
  args = Array.prototype.splice.call(arguments, 0);

  // get the `hook` and `hookArgument` variables 
  event = args.splice(0,1)[0]; // The first parameter, always the hook's name
  eventArguments = args;       // The leftovers, the hook's parameters

  // If the last parameter is a function, it's assumed
  // to be the callback
  if( typeof( eventArguments[ eventArguments.length-1 ] ) === 'function' ){
    callback = eventArguments.pop();   // The last parameter, always the callback
  }

  var listeners = this.listeners( event );

  listeners.forEach( function( listener ) {

      // Pushes the async function to functionList. Note that the arguments passed to invokeAll are
      // bound to the function's scope
      functionList.push( function( done ){
          listener.apply( this, Array.prototype.concat( eventArguments, done ) );
      } );
  });
  callback ? async.series( functionList, callback ) : async.series( functionList );
}

这是一个简单的测试方法：

asyncEvents = new AsyncEvents();

asyncEvents.onAsync('one', function( paramOne1, done ){
  done( null, paramOne1 + ' --- ONE done, 1' );
});

asyncEvents.onAsync('one', function( paramOne2, done ){
  done( null, paramOne2 + ' --- ONE done, 2' );
});

// Uncomment this and async will fail
//asyncEvents.onAsync('one', function( paramOne3, done ){
//  return paramOne3 + ' --- ONE done, 3' ;
//});

asyncEvents.onAsync('two', function( paramTwo, done ){
  done( null, 'TWO done, 1' );
});


asyncEvents.emitAsync('one', 'P1', function( err, res ){
  console.log( err );
  console.log( res );
});

asyncEvents.emitAsync('two', 'P2', function( err, res ){
  console.log( err );
  console.log( res );
});

谢谢！

Answer 1

这根本做不到。故事结束。