从另一个类内部调用方法

Question

I have a node class like this:

var Classes = function () {
};

Classes.prototype.methodOne = function () {
    //do something
};

when i want to call methodOne , i use this:

this. methodOne();

And it works. But right now i have to call it from inside of another method of another class. This time its not works and cant access to methodOne :

var mongoose = new Mongoose();
mongoose.save(function (err, coll) {
  //save to database
  this. methodOne(); //this does not work
}

how i can call methodOne? i use Classes.methodOne() but it's not work

Answer 1

this inside the save callback is in a new context and is a different this than the outside one. Preserve it in a variable where it has access to methodOne

var that = this;
mongoose.save(function (err, coll) {
  //save to database
  that.methodOne();
}

Answer 2

You need to create variable outside of mongoose function.

var self = this;

var mongoose = new Mongoose();
mongoose.save(function (err, coll) {
  //save to database
  self.methodOne(); //If you call `this` from here, This will refer to `mongoose` class
}

If you are in an environment that works with ES6 you can use the Arrow expression :

var mongoose = new Mongoose();
mongoose.save((err, col) => {
    //save to database
    this.methodOne();
})

Answer 3

What you can do is create an object of class Classes inside your other class and refer that method using this object: Ex:

var objClasses;
var mongoose = new Mongoose();
mongoose.save(function (err, coll) {
  //save to database
objClasses = new Classes();
  objClasses. methodOne(); //this should work
}

If it doesn't work please explain what exactly you want to achieve.