javascript - Mysql 和 node async.waterfall

Question

我正在尝试查明该记录是否存在于我的数据库表中。如果那里不存在，那么我想将它添加到我的数据库中。我使用 Node 并使用 async.waterfall。但是我的代码有问题，我找不到什么。它不会将记录添加到我的数据库中。有什么建议吗？

var mysql       = require('mysql');
var connection  = mysql.createConnection({
  host     : 'localhost',
  user     : 'user',
  password : 'password',
  database : 'database'
});


for (var m = 0; m <= (urls.length-1); m++) {
     var Myurl = urls[m];
     var ThisName= TheNames[m];

     //IIFE function. I omitted the error handling for clarity.

     (function(Myurl,ThisName){

        async.waterfall([

          //First find out if the record exists in mydata
          function(next){
          connection.query('SELECT * FROM mydata WHERE UrlLink=?   
                            LIMIT 1',[Myurl],next)
                        },

          //If the record does not exist, put it in mydata
          function(results,next){
          if (results.length==false){
              console.log("New Thing!");
              //Do some stuff here, request(Myurl...) to find TableName.
              var post  = {UniqueUrl:Myurl,ThingName:ThisName,TheName:TableName};
              connection.query('Insert INTO mydata Set ?', post,next);
                                    };
                                };
                         ],

          //Final callback
          function(err, results) {
          connection.end();
                                 };
                       );
     })(Myurl,ThisName);
   };

编辑:

在 if 语句中的 return next() 行，我得到了建议的答案 TypeError: object is not a function 的错误>。在我的真实代码中，我实际上做了类似的事情(当我使用建议的答案时):

async.series([
  //First function
  function(callback){
    //Some calculations...
    callback();
 },
  //Next function
  function(callback){
       var i = 0;
       //Loop
       async.whilst(
       function() { return i <= thefooz.length-1; },
       //The innerCallback:
       function(innerCallback){
       //Some calculations where i get urls and TheNames.
async.forEachOf(urls, function(Myurl, m, eachDone) {
  var ThisName = TheNames[m];

  async.waterfall([
    function(next) {
      connection.query(
        'SELECT * FROM mydata WHERE UrlLink=? LIMIT 1',
        [ Myurl ],
        next
      );
    },
    function(results, next) {
      if (results.length !== 0) {
        return next();
      }
      console.log("New Thing!");
      //Do some stuff here, request(Myurl...) to find TableName.
      var post = {
        UniqueUrl : Myurl,
        ThingName : ThisName,
        TheName   : TableName
      };
      connection.query('Insert INTO mydata Set ?', post, next);
    }
  ], eachDone);

}, function(err) {
  if (err) throw err; // or however you like to handle errors
  connection.end();
});
setTimeout(function() { i++; innerCallback(); }, 10000);
}); //close my calculations in innerCallback.
     }, //close innerCallback.

    ); //close asyns.whilst
callback;
   } //close function(callback)

      ], function(error){
        if (error) return next(error);

      });

我真的陷入了回调 hell ...

Answer 1

一个(未经测试的)版本应该做同样的事情，但在利用更多 async 的好处方面有一些错误修正和增强:

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'user',
  password : 'password',
  database : 'database'
});

// Process all url's in parallel (at the same time). If you to process them
// sequentially (one after another), you can use `async.forEachOfSeries()`
// instead. Or, if you want to limit the number of parallel requests, use
// `async.forEachOfLimit()`.

async.forEachOf(urls, function(Myurl, m, eachDone) {
  var ThisName = TheNames[m];

  async.waterfall([
    function(next) {
      connection.query(
        'SELECT * FROM mydata WHERE UrlLink=? LIMIT 1',
        [ Myurl ],
        next
      );
    },
    function(results, fields, next) {
      if (results.length !== 0) {
        return next();
      }
      console.log("New Thing!");
      //Do some stuff here, request(Myurl...) to find TableName.
      var post = {
        UniqueUrl : Myurl,
        ThingName : ThisName,
        TheName   : TableName
      };
      connection.query('Insert INTO mydata Set ?', post, next);
    }
  ], eachDone);

}, function(err) {
  if (err) throw err; // or however you like to handle errors
  connection.end();
});

除了使用forEach*，您还可以使用each*，但由于您还需要数组索引，forEach* 是更多方便。

相关文档:

• > async.forEachOf
• > async.forEachOfSeries
• > async.forEachOfLimit