0

在这里，我试图创建一个带有 Async.js 参数的函数数组。

该数组由 RunRequest 的实例组成，这些实例应该设置在 MakeRequest 的循环内，就在我尝试将函数数组传递给 Async 之前。

因此，当我将 request[i] 中的请求传递给 RunRequest 时，它很好，但在 RunRequest 函数内部它是未定义的？

// Process Requests
function RunRequest(db, collection, request, requestHandler, callback) {
    console.log('this happening?')
    // Connect to the database
    db.open(function(err, db) {
        if(err) callback(err, null);
        // Connect to the collection
        db.collection(collection, function(err, collection) {
            if (err) callback(err, null);
            // Process the correct type of command
            requestHandler(db, collection, request, callback);  
        });
    });
}

function MakeRequest(request, requestHandler, collection, callback) {
    var data = [];
    var doneRequest = function(err, results) {
        console.log('done was called')
        if (err) callback(err, null);
        else if(results) data = data.concat(results);
    }
    // Make Request Array
    var requestArray = [];
    for(var i = 0; i < request.length; i++) {
        console.log('run request was called')
        var dbConnection = new Db('KidzpaceDB', new Server(Host, Port, {auto_reconnect: true}))
        requestArray.push(function() {RunRequest(dbConnection, collection, request[i], requestHandler, doneRequest)});
    }
    // Make all requests in Parallel then invoke callback
    Async.parallel(requestArray, function(err, results) {
        console.log('Step WORKS')
        if(data) {
            var uniqueResults = [];
            for(var i = 0; i < data.length; i++) {
                if( !uniqueResults[data[i]['_id']] ) {
                    uniqueResults[uniqueResults.length] = data[i];
                    uniqueResults[data[i]['_id']] = true;
                }
                callback (null, uniqueResults);
            }
        }
    });
}


// Request Handlers
var FindHandler = function(db, collection, request, callback) {
    console.log('FindHandler was called')
    console.log('Request Query' + request);
    collection.find(request.query, function(err, cursor) {
        if (err) callback(err, null);
        cursor.toArray(function(err, docs) {
            if (err) callback(err, null);
            if(docs.length <= 0) console.log("No documents match your query");
            var requestResults = [];
            for(var i=0; i<docs.length; i++) {
                requestResults[requestResults.length] = docs[i]; 
            }
            db.close();
            callback(null, requestResults);
        });
    });
}
4

2 回答 2

1

这只是在黑暗中拍摄：

我认为问题在于您如何调用RunRequestinside MakeRequest。在第一个 for 循环中，您正在迭代request并request[i]在匿名函数中使用，但i在下一次迭代中发生更改，并且当前范围在RunRequest实际执行时会丢失。

很难重现，但试试这个：

var requestArray = [];
for(var i = 0; i < request.length; i++) {
    console.log('run request was called')
    var dbConnection = new Db('KidzpaceDB', new Server(Host, Port, {auto_reconnect: true}))

    function wrap(dbConnection, collection, request, requestHandler, doneRequest) {
        return function() {
            RunRequest(dbConnection, collection, request, requestHandler, doneRequest);
        }
    }
    requestArray.push(wrap(dbConnection, collection, request[i], requestHandler, doneRequest));
}
于 2012-09-13T07:48:16.957 回答
0

这是一个范围界定问题。当循环结束变量i设置为 时，也是request.length如此。request[i]undefined

用这样的匿名函数包装你的代码：

var requestArray = [];
for(var i = 0; i < request.length; i++) {
    (function(i) {
        console.log('run request was called');
        var dbConnection = ...;
        requestArray.push( ... );
    })(i);
}

甚至更好（在创建匿名函数时避免不必要的开销）：

var requestArray = [];
request.forEach( function( el ) {
    console.log('run request was called');
    // the other code goes here, use el instead of request[i]
});

编辑未调用回调，因为您没有正确定义数组中的函数。您将不得不稍微重构您的代码，所以让我向您展示它应该是怎样的：

requestArray.push(function(callback) { // <---- note the additional parameter here
    // do some stuff, for example call db
    db.open(function(err, db) {
        if (err) {
            callback( err );
        } else {
            callback( );
        }
    });
});

如果你想使用RunRequest，那么你需要callback作为附加参数传递给RunRequest（所以使用callback而不是doneRequest）。

于 2012-09-13T07:57:16.693 回答