節點JS，快遞，貓鼬，嵌套查詢

Question

我有一組快遞/貓鼬嵌套查詢的，非常像這樣：

app.get(..., function(...) { 

    Schema1.query(..., function(..., res1) { 

     for (var key in res1) { 
      Schema2.query(..., function(..., res2) { 
      data[key].appendedAttribute = res2.somedata; 
      }); 
     } 

     res.render(..., data); 
    }); 

}）;

哪個不起作用，即，appendAttribute永遠不會附加到數據集。我究竟做錯了什麼？

Answer 1

使用after

app.get(..., function(...) { 
    Schema1.query(..., function(..., res1) { 
     var cb = after(Object.keys(res1).length, function() { 
      res.render(..., data);  
     }); 

     for (var key in res1) { 
      Schema2.query(..., function(..., res2) { 
       data[key].appendedAttribute = res2.somedata; 
       cb(); 
      }); 
     } 
    }); 
}); 

基本上第二個查詢完成後，你必須只火res.render電話。

Answer 2

使用Step：

app.get(..., function(...) { 
    var data; 
    Step(
    function first_query() { 
     Schema1.query(...,this); 
    }, 
    function multiple_queries(err, res1) { 
     for (var key in res1) { 
     Schema2.query(..., function(..., res2) { 
      data[key].appendedAttribute = res2.somedata; 
      this.parallel(); // make sure callback gets executed only after all the queries are executed 
     }); 
     }  
    }, 
    function render() { 
     res.render(..., data); 
    } 
); 
});