exports.create = function(req, res) {
var company_id = req.company_id;
var client = new Client(req.body);
Company.findOne({_id: company_id}, function(err, company) {
if(err) {
response = {
status: 'error',
error: err
}
return res.json(response);
} else if(!company) {
response = {
status: 'error',
error: 'Invalid company_id'
}
return res.json(response);
} else {
client.save(function(err) {
if(err) {
response = {
status: 'error',
error: err
}
} else {
response = {
status: 'ok',
client: client
}
}
return res.json(response);
});
}
});
}
That's my code (using Express, if it matters). I'm trying to learn more about promises, specifically with Q. I feel that this is the perfect kind of logic that can be implemented with promises to avoid this hairy conditional nest. But I'm not sure how to start?
But I'm not sure how to start?
Start by removing the callbacks and using the Promise methods instead. Then put the error handling in a dedicated error callback, instead of using that condition. Also, you can put the code for building that response object in the very end (removing the duplication), and only pass/throw the err down to it.
exports.create = function(req, res) {
var client = new Client(req.body);
Q.ninvoke(Company, "findOne", {_id: req.company_id}).then(function(company) {
if(!company)
throw 'Invalid company_id';
else
return company;
}).then(function(company) {
return Q.ninvoke(client, "save");
}).then(function(saveResult) {
return {
status: 'ok',
client: client
};
}, function(err) {
return {
status: 'error',
error: err
};
}).done(function(response) {
res.json(response);
});
};
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