Question

I have simple example:

function File(name) {
   this.name = name
   this.text = null
}

File.prototype = {
    read: function() {
         fs.readFile(this.name, function (err, data) {
     }
    },
    getContent: function() {
         return this.text
     }
}

var myfile = new File('my_file')

watch.createMonitor('my_file_dir', function (monitor) {
    monitor.files['my_file']
    monitor.on("change", function (f, stat) {
        myfile.read()
    }
})

  main program....:

   myfile.getContent() ...

I want to add file contents in this.text variable. How to do it ?

Answer 1

• Create local variable and store there ‘this’

  read: function() {
  var _file = this;
  fs.readFile(this.name, function (err, data) {
  …
  _file.text = data;
  …
  });
  },

• Bind ‘this’ to inner function:
  read: function() {

   fs.readFile(this.name, function (err, data) {
       ...
       this.text = data;
       ...
   }.bind(this)
  

  },

Note:
It’s insufficiently to store data to this.text: if you read something asynchronously in yur class, you need to provide callbacks to let other objects know that you got some data in yourFile.text