Question

我正在关闭“finally”块中的写连接，但即使进入此块后，程序似乎又回到了try块。这是代码：

    function printAllAssetsAndThreats(startX, startY) {
      try {

    con.query("SELECT * FROM Kunde1Assets;", function (err, result, fields) {
      for (var i in result) {
        console.log("b");
        myDoc.font('Helvetica-Bold')
        .fontSize(20)
        .text('str', startX, startY);

        var xxx = result[i].KundenAssetID;

        startY = startY + 50;
        //jetzt jeweils alle gefährdungen:
        var sql = "SELECT DISTINCT c.AID, b.GID, b.Name, c.Name AS Asset  FROM Kunde1Verbindungen a, Gefährdungen b, Kunde1Assets c  WHERE a.KundenAssetID =  \"" + xxx + " \"AND a.GID = b.GID  AND c.KundenAssetID = a.KundenAssetID";
        con.query(sql, function (err, result2, fields) {
          for (var i2 in result2) {

          }
        });
        ///////////////////



      }
    });
  } catch (e) {
  } finally {
    console.log("a");
    end();
  }
}

因此，即使在打印“a”后，控制台中也会打印出“b”。谢谢你的帮助!!!

蒂姆

修改

我试过重写代码f.e.有回调但它仍然无法正常工作

start(()=>{

  myDoc.end();
});

 function start(callback){
  console.log("hello");
  myDoc.font('Helvetica-Bold')
  .fontSize(20)
  .text('str', 44,44);
    con.query("SELECT * FROM Kunde1Assets;", function (err, result, fields) {
      console.log("hello");
      var counter=0;
   for(var i in result){
     console.log("hello");
     start2(result[i].KundenAssetID, ()=>{});
     counter++;
      if (counter==result.length){
     console.log("yo");break;callback();
   }
   if (counter==result.length){
    console.log("yo");callback();
  }

   }
//


      });

}
 function start2(kaid, callback){
        var sql = "SELECT DISTINCT c.AID, b.GID, b.Name, c.Name AS Asset  FROM Kunde1Verbindungen a, Gefährdungen b, Kunde1Assets c  WHERE a.KundenAssetID =  \"" + kaid + " \"AND a.GID = b.GID  AND c.KundenAssetID = a.KundenAssetID";
        con.query(sql, function (err, result2, fields) {
          for (var i2 in result2) {
            console.log(kaid +"---"+ result2[i2].Name);
            myDoc.font('Helvetica-Bold')
            .fontSize(20)
            .text('str', 44,44);
          }
        });

}

编辑：用承诺（还没有工作）尝试了它

myDoc.pipe(fs.createWriteStream('node.pdf'));

var promise = start();
promise.then(function(result){

  console.log(result);
  myDoc.end();
})  
   function start(){
     return new Promise (function(resolve, reject){
      con.query("SELECT * FROM Kunde1Assets;", function (err, result, fields) {
        console.log(result);
        for (var i in result){
           myDoc.font('Helvetica-Bold')
          .fontSize(20)
          .text(result[i].Name, 30, 20+(i*30));

          var promise2 = start2 (result[i].KundenAssetID);
          promise.then(function(name){
            for (var i2 in name){
              myDoc.font('Helvetica-Bold')
              .fontSize(20)
              .text('result[i].Name', 30, 20+(i2*30));
            }
          });
        }

        resolve(result);
        if (Error) reject();
        });
     }); 
  }


   function start2(kaid){
     return new Promise(function( resolve, reject){
       var sql = "SELECT DISTINCT c.AID, b.GID, b.Name, c.Name AS Asset  FROM Kunde1Verbindungen a, Gefährdungen b, Kunde1Assets c  WHERE a.KundenAssetID =  \"" + kaid + " \"AND a.GID = b.GID  AND c.KundenAssetID = a.KundenAssetID";
          con.query(sql, function (err, result2, fields) {
            for (var i2 in result2) {
              //console.log(kaid +"---"+ result2[i2].Name);


            }
           resolve(result2);
           if (Error) reject();
          });
     });       
  }

Answer 1

您的try/catch/finally块正在同步运行。它将在JS事件循环的第一个刻度内点击finally。但是（我假设，基于回调的结构），con.query()函数是异步的。这意味着它最终将在中运行至少。因此，这将始终在finally中的所有内容之后运行。

如果您希望它按预期工作，请查看实现try/catch/finally结构的异步方法。有一百万种方法可以对猫，异步库，承诺等进行换肤。或者只是在连接回调中的连接之后保留你想要运行的任何代码。

无论哪种方式，问题都是同步和异步代码相互并存的组合。

Javascript pdfKit“错误：写完后”由于封闭流...？

1 个答案: