风帆的JavaScript灰烬

Question

I'm working with EmberJS and SailsJS. Now I've been asked to make a statistics page and handle the filtering process in the SailsJS.

I have a model for departments and another model for requests the relationship between these models is (request belongsTo department). For some reason my manager prevented me to make a (hasMany) relationship.

Now what I want to do is to loop through all the departments and store them in new Object, inside that loop I want to loop through all the requests by Using Request.count({where : { department : department.id }}) and get the number of requests for each department in the departments Array Of Object.

I tried to do it as I explained but the problem is when I log the department inside the request loop it gives me the result as I imagined but when I add (.id) it shows me 'undefined'.

Here is my code:

Department.find().then((departments) => {
    report.departments = departments;
    Request.count({ department : departments.id}).exec(function countMe(err, count) {
       console.log(count);
    })
})

PS: if there's any other approach for this task please tell me, I'm kind of a beginner.

Answer 1

Your departments object in the .then callback is an array of department objects. To get an id you'd need to do something like departments[0].id .

I might not recommend using .count because that means a separate trip to the database for each department. Sails waterline may have some way for you to count up Requests grouped by department id, but just to get a steamroller working example, I would first just get everything and do some processing in your code:

Department.find().then((departments) => {
    Request.find().then((requests) => {
        var requestCounts = {}; // we'll store the counts in this object
        for (var idx = 0; idx < requests.length; idx++) {
            if (!requestCounts[requests[idx].department]) {
                requestCounts[requests[idx].department] = 0;
            }
            requestCounts[requests[idx].department]++;
        }
        // use requestCounts...
    });
});

Creating a separate object like that may not be what you want to do, but something like this should serve whatever purpose you have. Notice, the code I wrote did not require finding all the department objects, but whatever you are doing likely will...

If you're interested in efficiency, then once you get this working, you can see if there is some way you can query the database to directly get the counts you want instead of this in-code processing. But I would start with something simple like this.

---

EDIT:

It sounds like you may be able to use something like:

Request.find().groupBy('department').sum('count').exec(function (err, results){
    console.log(results);
});

But I'm finding conflicting reports on whether this works with sails-mongo, so take this as a "maybe this will work" recommendation.

Answer 2

I assume Request has a property department which is an ObjectId related to departments.

The quick one is to correct the following:

• the 2nd line does not make sense as reports is not used

• do

  let departmentIds = _.map(departments, 'id');

and use departmentIds in the count query object

However, you are anyway finding all departments in the initial query, I would assume you count all the Requests anyway. Finding the departments first only makes sense in case you have query object there limiting the number of returned departments.

In addition, if you know the departmentIds in question you might not need to query them. Otherwise you might use a projection to just return the departmentIds instead of all the properties of all the departments