Access request headers from beforeSave Model Hook

Question

How can i access the details of the user who raise the request from a Model Hook

Comment.beforeSave =  function(next,com) {
//Want to add 2 more properties before saving 
com.added_at = new Date();    
com.added_by =  //How can i set the user id here ??
//In case of a Remote hook i have ctx in param and i can get user id like this     ctx.req.accessToken.userId;  But in Model Hook how can i do the same?    
next();    
};

Is there any way to do this? I tried with Remote hook for main Item in the way

MainItem.beforeRemote('**', function(ctx, user, next) {   
if(ctx.methodString == 'leave_request.prototype.__create__comments'){       
    ctx.req.body.added_by = ctx.req.accessToken.userId;     
    ctx.req.body.added_at = new Date();                         
    console.log("Added headers as .."+ctx.req.body.added_by);
}    
else{   
    ctx.req.body.requested_at = new Date();
    ctx.req.body.requested_by = ctx.req.accessToken.userId; 
    console.log("Added header @ else as .."+ctx.req.body.requested_by);
}
next();

});

And i get the console logs properly once i make request from explorer , but But the explorer always return me the error

"error": {
    "name": "ValidationError",
    "status": 422,
    "message": "The `comment` instance is not valid. Details: `added_by` can't be blank; `added_at` can't be blank.",
    "statusCode": 422,
    "details": {
      "context": "comment",
      "codes": {
        "added_by": [
          "presence"
        ],
        "added_at": [
          "presence"
        ]
      },
      "messages": {
        "added_by": [
          "can't be blank"
        ],
        "added_at": [
          "can't be blank"
        ]
      }
    },
    "stack": "ValidationError: The `comment` instance is not valid. Details: `added_by` can't be blank; `added_at` can't be blank.\n   "
  }
}

and my model is like

 "properties": {
"body": {
  "type": "string",
  "required": true
},
"added_by": {
  "type": "number",
  "required": true
},
"added_at": {
  "type": "date",
  "required": true
},
"leave_request_id":{
  "type": "number",
  "required": true
}

}

Answer 1

It seems that you can't update related model with simply overriding ctx.req.body. Instead of you should override ctx.args.data - it looks like this ctx parameter is used to initalize the related model.

So it will look like that:

MainItem.beforeRemote('**', function(ctx, user, next) {   
  if(ctx.methodString == 'leave_request.prototype.__create__comments'){  
     ctx.args.data.added_by = ctx.req.accessToken.userId;     
     ctx.args.data.added_at = new Date();                         
     console.log("Added headers as .."+ctx.args.data.added_by);
  }    
  else{  ... }
  next();

Answer 2

The beforeRemote hooks execute before the model hooks, so you can add the userId to the request body.

Comment.beforeRemote('**', function (ctx, unused, next) {
    var userId = ctx.req.accessToken.userId;
    if (ctx.methodString == 'Comment.create' || ctx.methodString == 'Comment.updateAttributes') {
        ctx.req.body.userId = userId;
    }
    next();
});

you might want to review which methodstring suit you best.

Answer 3

Faced with the same problem, I used node expiremantal domain feature (that intended for error handling).

Saving incoming request object:

// -- Your pre-processing middleware here --
app.use(function (req, res, next) {
  // create per request domain instance
  var domain = require('domain').create();

  // save request to domain, to make it accessible everywhere
  domain.req = req;
  domain.run(next);
});

Next inside model hook you have access to req object, which is created per each connection:

process.domain.req 

Also StrongLoop team added context propagation (based on continuation-local-storage), but it is not documented yet.

Answer 4

I solved this by adding the middleware for body parsing. In the middleware.js I wrote the following code:

...
"parse": {
   "body-parser#json": {},
   "body-parser#urlencoded": {"params": { "extended": true }}
},
...

Also, in the server.js I added the require for the body parser and multer:

var loopback = require('loopback');
...
var bodyParser = require('body-parser');
var multer = require('multer');
...

app.use(bodyParser.json()); // application/json
app.use(bodyParser.urlencoded({ extended: true })); // application/x-www-form-urlencoded
app.use(multer()); // multipart/form-data
...

Then add the dependencies in the package.json

"body-parser": "^1.12.4",
"multer": "^0.1.8"

Now you can do things like the following in the /models/user.js (for any model)

  user.beforeRemote('create', function(ctx, unused, next) {
     console.log("The registered user is: " + ctx.req.body.email);
     next();
  });

I hope this helps! :)

Answer 5

If we assume that there is a relation comments of User -> Comment, you may also to try relation method POST /users/{user_id}/comments which will populate the foreignId (which can be added_by).

Another thing is added_at. As far as I understand, validation hook is triggered before create hook. It means that validation will fail, since this field is marked as required in a model. The question is whether this field should be marked as required, since it is set by the server, and not required to be set by the client of the API.