Custom responses
Overview
Sails apps come bundled with several pre-configured responses that can be called from action code. These default responses can handle situations like “resource not found” (the notFound response) and “internal server error” (the serverError response). If your app needs to modify the way that the default responses work, or create new responses altogether, you can do so by adding files to the api/responses folder.
Note:
api/responsesis not generated by default in new Sails apps, so you’ll have to add it yourself if you want to add / customize responses.
Using responses
As a quick example, consider the following action:
getProfile: function(req, res) {
// Look up the currently logged-in user's record from the database.
User.findOne({ id: req.session.userId }).exec(function(err, user) {
if (err) {
res.status(500);
return res.view('500', {data: err});
}
return res.json(user);
});
}
This code handles a database error by sending a 500 error status and sending the error data to a view to be displayed. However, this code has several drawbacks, primarily:
- The response isn't content-negotiated: if the client is expecting a JSON response, they're out of luck
- The response reveals too much about the error: in production, it'd be best to just log the error to the terminal
- It isn't normalized: even if we dealt with the other bullet points above, the code is specific to this action, and we'd have to work hard to keep the exact same format for error handling everywhere
- It isn't abstracted: if we wanted to use a similar approach elsewhere, we'd have to copy / paste the code
Now, consider this replacement:
getProfile: function(req, res) {
// Look up the currently logged-in user's record from the database.
User.findOne({ id: req.session.userId }).exec(function(err, user) {
if (err) { return res.serverError(err); }
return res.json(user);
});
}
This approach has many advantages:
- More concise
- Error payloads are normalized
- Production vs. development logging is taken into account
- Error codes are consistent
- Content negotiation (JSON vs HTML) is taken care of
- API tweaks can be done in one quick edit to the appropriate generic response file
Response methods and files
Any .js file saved in the api/responses/ folder can be executed by calling res.thatFileName(). For example, api/responses/insufficientFunds.js can be executed with a call to res.insufficientFunds().
Accessing req, res, and sails
The request and response objects are available inside of a custom response as this.req and this.res. This allows the actual response function to take arbitrary parameters. For example:
return res.insufficientFunds(err, { happenedDuring: 'signup' });
And the implementation of the custom response might look something like this:
module.exports = function insufficientFunds(err, extraInfo){
var req = this.req;
var res = this.res;
var sails = req._sails;
var newError = new Error('Insufficient funds');
newError.raw = err;
_.extend(newError, extraInfo);
sails.log.verbose('Sent "Insufficient funds" response.');
return res.badRequest(newError);
}
Built-in responses
All Sails apps have several pre-configured responses like res.serverError() and res.notFound() that can be used even if they don’t have corresponding files in api/responses/.
Any of the default responses may be overridden by adding a file with the same name to api/responses/ in your app (e.g. api/responses/serverError.js).
You can use the Sails command-line tool as a shortcut for doing this.
For example:
sails generate response serverError
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