CODEWITHSUNDEEP
javascriptnode.jsexpressprototype
britztopher
britztopher

Reputation: 1234

Lost Context when Using 'this' within Prototype Method

Ok, so I have a node application that uses express. Within this application I have an express route like so:

var   MyObj = require('./myObj')
    , myObj = new MyObj();    
app.post('/api/blah', auth.requiresLogin, myObj.method2);

Now within the MyObj object I have the following:

var MyObj = function(name){
    this.name = name;
    this.message = 'hello';

};

MyObj.prototype = {
  method1: function(req, res, done){
    console.log('In Method 1');
    done(null, this.message +' '+this.name);
  },
  method2: function(req, res){

    var message;

    console.log('In Method 2');

    this.method1(req, res, function(err, value){
      if(err) throw err;
      message = value;
      console.log(this.message);
    });

    return message;
  }
};

module.exports = MyObj;

Now if I dont require this object and call it from within the same file it works. As demonstrated on this jsFiddle: http://jsfiddle.net/britztopher/qCZ2T/. However, if i require it, construct it with new, and try to call myObj.method2(req, res); from the requiring class I get #<Object> has no method 'method1'. Dont know what I am doing wrong here, or if its expressJS or require JS thats giving me issues. Also, when i look inside this when in method2 it is this = global, so something is losing this' context.

Upvotes: 2

Views: 871

Answers (1)

Hampus
Hampus

Reputation: 2799

When passing the myObj.method2 method as a parameter to app.post you are not telling in which context/scope it should execute. Therefore it will execute in the global scope. The solution should be myObj.method2.bind(myObj).

Upvotes: 1

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