How can I pass data between hooks

[projectxmaker]

Hi,

I would like to pass data between hooks, but don't know how, if I set it as global variable under module.export in modelName.js, it's not safe between requests.

for example:

• beforeRemote: I have a variable modelData = A.
• afterRemote: I would like to use variable modelData at this phase.

thanks for any help :)

@bajtos do you have any idea ^^

[bajtos]

Add them to the ctx object.

Customer.beforeRemote('**', function(ctx, unused, next) {
  ctx.modelData = "A";
  next();
});

Customer.afterRemote('**', function(ctx, unused, next) {
  console.log('modelData', ctx.modelData);
});

[bajtos]

See #337 for a more advanced solution that can be used to access context data from any method.

[projectxmaker]

👍 cool, thanks for your help

[projectxmaker]

@bajtos
another question, I just read #337, but had no luck to find a way to get context object from model instance or even from a model hook (beforeCreate, afterCreate, etc).

module.exports = function(modelName) {
  // I'd like to get the context here, is there any way ?
  var a = modelName.[somehow].ctx.modelData; 

  // or even in model hook ?
  modelName.beforeSave =  function(next, mdl) {
    var a = mdl.[somehow].ctx.modelData;
  }
}

^^

[bajtos]

var ctx = loopback.getCurrentContext();

[bajtos]

  // I'd like to get the context here, is there any way ?
  var a = modelName.[somehow].ctx.modelData; 

There is no context at the time your model script is run, as the context is created always per incoming request.

  // or even in model hook ?
  modelName.beforeSave =  function(next, mdl) {
    var a = mdl.[somehow].ctx.modelData;
  }

This is where you can call loopback.getCurrentContext().

Keep in mind that loopback.getCurrentContext() is different from the ctx argument passed to beforeRemote and afterRemote hooks.

module.exports = function(Customer) {
  Customer.beforeRemote('**', function(remotingCtx, unused, next) {
    loopbackCtx = loopback.getCurrentContext();
    // save the value from `?someQueryParam=value`
    loopbackCtx.modelData = remotingCtx.req.query.someQueryParam;
    next();
  });

  Customer.beforeSave =  function(next, mdl) {
    loopbackCtx = loopback.getCurrentContext();
    this.contextData = loopbackCtx.modelData; // the value stored above
    next();
  };
};

[projectxmaker]

@bajtos thanks for your answer ^^

but I got error when trying to get "loopbackCtx" with "loopback.getCurrentContext()"

module.exports = function(Customer) {
  Customer.beforeRemote('**', function(remotingCtx, unused, next) {
    loopbackCtx = loopback.getCurrentContext();
    // save the value from `?someQueryParam=value`
    loopbackCtx.modelData = remotingCtx.req.query.someQueryParam;
    next();
  });

returned error is about "has no method 'getCurrentContext"

"name": "TypeError",
    "status": 500,
    "message": "Object function createApplication() {\n  var app = express();\n\n  merge(app, proto);\n\n  app.loopback = loopback;\n\n  // Create a new instance of models registry per each app instance\n  app.models = function() {\n    return proto.models.apply(this, arguments);\n  };\n\n  // Create a new instance of datasources registry per each app instance\n  app.datasources = app.dataSources = {};\n\n  // Create a new instance of connector registry per each app instance\n  app.connectors = {};\n\n  // Register built-in connectors. It's important to keep this code\n  // hand-written, so that all require() calls are static\n  // and thus browserify can process them (include connectors in the bundle)\n  app.connector('memory', loopback.Memory);\n  app.connector('remote', loopback.Remote);\n\n  return app;\n} has no method 'getCurrentContext'",
    "details": null

I did something wrong or anything missing ? :(

[bajtos]

See the discussion in #775.

You must ensure that loopbak.context middleware was run before you can call loobpack.getCurrentContext. The context middleware is usually called by loopback.rest() for you. If your setup is nonstandard, then you must add the middleware manually yourself.

[bajtos]

Actually, the context middleware was not released yet. You have to use loopback from github master to get this new feature:

$ npm install strongloop/loopback

[bluestaralone]

"Keep in mind that loopback.getCurrentContext() is different from the ctx argument passed to 
beforeRemote and afterRemote hooks.". 

@bajtos
Can you tell me what are different between them ?

And another problem is when i request with accessToken was set: "loobpack.getCurrentContext" return null.

[bajtos]

Can you tell me what are different between them ?

They are different objects created at different places, thus they don't share the same properties.

Also you have to use .get(name) and .set(name, value) to work with the data in the loopback context, while the remoting context uses plain properties.

And another problem is when i request with accessToken was set: "loobpack.getCurrentContext" return null.

That happens when loopback.context was not executed yet for the given requests. That has usually two sources:

• you have loopback.token was added before loopback.context (it should be the other way around)
• you are calling the method outside of a request, e.g. from a boot script

[bluestaralone]

@bajtos
I just used your example to test and didn't change anything.
I tested on https://github.com/strongloop/loopback-example-app
Step to create bug like this:

1. run npm install strongloop/loopback
2. Copy your code into Customer.js
3. Add debug codes
4. Run app
5. Go to explorer page and make a request GET /Customers
6. Go to explorer page and Login to get AccessToken
7. Go to explorer page and set AccessToken to header in Explorer page
8. Go to explorer page and make a request GET /Customers
9. Check console log

My code:

var loopback = require('loopback');

module.exports = function(Customer) {

  Customer.beforeRemote('**', function(remotingCtx, unused, next) {
    loopbackCtx = loopback.getCurrentContext();
    console.log("beforeRemote", loopbackCtx);
    loopbackCtx.modelData = 'aaaaaaaaaaaaaaa';
    next();
  });

  Customer.beforeSave =  function(next, customer) {
    loopbackCtx = loopback.getCurrentContext();
    console.log("beforeSave", loopbackCtx);
    next();
  };
};

and my log:

supervisor running without clustering (unsupervised)
Browse your REST API at http://localhost:3000/explorer
Web server listening at: http://localhost:3000/
beforeSave null
beforeSave null
beforeSave null
beforeSave null
beforeRemote { name: 'loopback',
  active: { accessToken: undefined },
  _set: [ null, { accessToken: undefined } ],
  id: 
   { create: [Function],
     flags: 15,
     before: [Function],
     after: [Function],
     error: [Function],
     uid: 1,
     data: null } }
beforeRemote null

[bluestaralone]

@bajtos

you have loopback.token was added before loopback.context 
(it should be the other way around)

Where can i place both of them ?

[bajtos]

@bluestaralone I just used your example to test and didn't change anything.

Please open a new issue to track this problem and repost the steps, the code and the log there.

[bluestaralone]

ok, thanks

[projectxmaker]

@bajtos thanks for your answers, I am currently working with @bluestaralone and we are looking forward to your support on #809 :)