Can't set headers after they are sent without additional res statements

Question

Using sailsjs v0.12.1

index: function(req, res) {
    Customer.find().populate('projects').exec(function(err, customers) {
        customers.forEach(function(customer, index) {
            customer.projects.forEach(function(project, index) {
                // Find project contributors and attach to project
                ProjectContributor.find({
                    project: project.id
                }).populate('user').exec(function(err, contributor) {
                    project.contributor = contributor;

                    return res.json(customers);
                });
            });
        });
    });
}

This triggers Error: Can't set headers after they are sent. . The interesting thing here is that this error isn't triggered always - everything worked fine ~30 minutes ago.

There's no other return res.x statement anywhere else in this controller.

Answer 1

You need to install the async library first.

npm install async --save

Then you can use the following code

var async = require('async');
// ...
// ...
Customer.find().populate('projects').exec(function(err, customers) {
    var tArray = [];
    async.each(customers, function(customer, cb) {
        var aCustomer = customer; // might want to deep copy it?
        aCustomer.projects = [];
        async.each(customer.projects, function(project, projectCB) {
            ProjectContributor.find({
                project: project.id
            }).populate('user').exec(function(err, contributor) {
                project.contributor = contributor;
                aCustomer.projects.push(project);
                projectCB();
            });
        }, function projectsDone(err) {
            tArray.push(aCustomer);
            cb();
        });
    }, function done(err) {
        return res.json(tArray);
    });
});

I haven't tested the code, but it should work just fine.

Answer 2

用异步库的每个函数（async.each）替换forEach语句。所有迭代结束后，将调用一个回调，然后在该回调中放置res.send（） 更多信息

Answer 3

I think you just had to write your:

return res.json(customers);

statement at the end of the forEach loop.