I'm new to Node from the lands of C#, PHP and Python. I've been working days in many variations of the same problem - how can I retrieve a set of data, based on that data, retrieve another set, then render the results out. I've tried the method below, event based (client.on("row")) and the async module and I can't get any to produce the right results. In the end, I'd like to pass a projects object with tasks added to Express to render.

我是C#,PHP和Python領域的新手Node。我已經在同一個問題的許多變體中工作了幾天 - 如何根據該數據檢索一組數據,檢索另一組,然后渲染結果。我已經嘗試了下面的方法,基於事件(client.on(“row”))和異步模塊,我無法得到任何產生正確的結果。最后,我想傳遞一個項目對象,其中任務添加到Express以進行渲染。

Could anyone help me out of this hole?

任何人都可以幫助我走出這個洞嗎?

exports.index = function(req, res){
req.session.user_id = 1;
if (req.session == undefined || req.session.user_id == null || req.session.user_id < 0) {
    res.redirect('/login');
} else {
    var pg = require('pg');
    var conString = "postgres://jason@localhost:5432/simpleproject";

    var client = new pg.Client(conString);

    client.connect(function(err) {
        client.query("SELECT * FROM project", function(err, projects) {



            for (var i=0; i<projects.rowCount; i++) {
                var project = projects.rows[i];

                client.query("SELECT * FROM task WHERE project_id="+projects.rows[i].id, function(err, subrows) {

                    if (subrows.rowCount > 0) {
                        project.tasks = subrows.rows;
                        console.log("adding tasks");
                    } else {
                        project.tasks = null;
                    }

                    if (i==projects.rowCount) {
                    console.log("rendering");
                    res.render('main', { title: 'My Projects', projects: projects });
                    }

                });
            }
            if (err != null) { console.log(err); }
        }
        );
    });     
}

};

UPDATE: Meryn below provides a good solution to my issue, just to share that information, in the end, below his code with a little touch up to get it to operate: (thanks Meryn!)

更新:下面的Meryn為我的問題提供了一個很好的解決方案,只是為了分享這些信息,最后,在他的代碼下面稍加修改以使其運行:(感謝Meryn!)

var async = require('async');

exports.index = function(req, res){
req.session.user_id = 1;
if (req.session == undefined || req.session.user_id == null || req.session.user_id < 0) {
    res.redirect('/login');
} else {
    var pg = require('pg');
    var conString = "postgres://jason@localhost:5432/simpleproject";

    var client = new pg.Client(conString);

    var addTasksToProject = function(projectRow, cb) { // called once for each project row
    client.query("SELECT * FROM task WHERE project_id="+projectRow.id, function(err, result) {
        console.log("tasks");
      if(err) return cb(err); // let Async know there was an error. Further processing will stop
      projectRow.tasks = result.rows;
      cb(null); // no error, continue with next projectRow, if any
    });
  };

  client.connect(function(err) {
      client.query("SELECT * FROM project", function(err, projects) {
        console.log("projects");
        if (err) return console.error(err);
        async.each(projects.rows, addTasksToProject, function(err) {
          if (err) return console.error(err);
          // all project rows have been handled now
          console.log(projects.rows);
          res.render('main', { title: 'My Projects', projects: projects.rows});
        });
      });
    });
}
};

1 个解决方案

  addTasksToProject = function(projectRow, cb) { // called once for each project row
    client.query("SELECT * FROM task WHERE project_id="+projectRow.id, function(err, result) {
      if(err) return cb(err) // let Async know there was an error. Further processing will stop
      projectRow.tasks = result.rows
      cb(null) // no error, continue with next projectRow, if any
    }
  }
  client.query("SELECT * FROM project", function(err, projects) {
    if (err) return console.error(err)
    async.each(projects.rows, addTasksToProject, function(err) {
      if (err) return console.error(err)
      // all project rows have been handled now
      res.render('main', { title: 'My Projects', projects: project.rows});
    })
  }