How to pass an argument of parent method to it's inner calling methods?

Question

I am trying to call a file uploader plugin. When a file is selected, the add method will be called from library. On calling add, I need to pass parent method argument opts with add method as argument.

Here is piece of code using with RequireJS library.

 return {            
        onFileChoose: function (e, data) {
            // I need 'opts' object here
        },
        start: function (opts) {
            $('fileupload').fileupload({
                url: '//testbucket.s3.amazonaws.com', // Grabs form's action src
                type: 'POST',
                autoUpload: true,
                dataType: 'xml', 
                add: this.onFileChoose
            });
        }
 }

I need the opts object in onFileChoose.

I tried with

add: function (e, data) {
    this.onFileChoose(e, data, opts);
}

Above code produces an error as this.onFileChoose is undefined.

How to solve this issue?

Answer 1

The problem is inside the callback method, this is not referring the object having the methods

Use a closure variable

return {            
    onFileChoose: function (e, data) {
        // I need 'opts' object here
    },
    start: function (opts) {
        var self = this;
        $('fileupload').fileupload({
            url: '//testbucket.s3.amazonaws.com', // Grabs form's action src
            type: 'POST',
            autoUpload: true,
            dataType: 'xml', 
            add: function (e, data) {
                self.onFileChoose(e, data, opts);
            }
        });
    }
}

or use $.proxy()

return {
    onFileChoose: function (e, data) {
        // I need 'opts' object here
    },
    start: function (opts) {
        $('fileupload').fileupload({
            url: '//testbucket.s3.amazonaws.com', // Grabs form's action src
            type: 'POST',
            autoUpload: true,
            dataType: 'xml',
            add: $.proxy(function (e, data) {
                this.onFileChoose(e, data, opts);
            }, this)
        });
    }
}