callbacksModelAnswerLearning1

appLearningMA.js

// dealing with the Location
var location = require('./learningLocation.js');
// dealing with the Weather
var weather = require('./learningWeather.js');
// test the script.
// this works!!

location(function(userLocation){
	console.log('Location is: ', userLocation);
}); 

// test the script
// this doesn't work!!!
weather(location,function(weatherData){
	console.log('Weather is: ', weatherData);
});

learningLocation.js

// learningLocation
// NB: Location is not dependent on any user input
// Location is obtained from the IP address

module.exports = function(callback){

	// define variables
	var url = "http://ipinfo.io";
	var request = require('request');

	// Notification
	console.log('Obtaining the location...');

	// Logic
	request({
		url: url,
		json: true
	}, function(error, response, body){
		if(error){
			callback('');
		} else {
			callback(JSON.stringify(body, null, 4));
		}
	});
};

learningWeather.js

module.exports = function(location, callback){
	// define variables
	var request = require('request');
	var encodedLocation = encodeURIComponent(location);
	var url = 'http://api.openweathermap.org/data/2.5/weather?q=' + encodedLocation + '&appid=a0405ca935c126bca3f178e0230f75b5&units=metric';


	// Check if no location is provided
	if (!location){
		return callback('No location provided'); // ie end the program here
	}

	// Notify the user
	console.log('Fetching the weather data...');

	// Apply logic
	request({
		url: url,
		json: true
	},function(error, response, body){
		if(error){
			callback('Unable to fetch the weather data!');
		} else {
			//console.log(JSON.stringify(body,null, 4));
			callback('In city: ' + body.name +  ' the temperature is:  ' + body.main.temp + ' deg C.');
		}
	});
};

learningWeatherExpt1.js

// define variables
var request = require('request');
var encodedLocation = encodeURIComponent('Sutton');
var url = 'http://api.openweathermap.org/data/2.5/weather?q=' + encodedLocation + '&appid=a0405ca935c126bca3f178e0230f75b5&units=metric';

// Notification.
console.log('LearningWeatherExpt1: Getting weather data...');

// Apply logic
request({
	url : url,
	json: true
}, function(error, response, body){
	if(error){
		console.log('Unable to fetch weather data!!')
	} else {
		console.log(JSON.stringify(body, null, 4));
		console.log("Town: " , body.name + ': Country ' + body.sys.country + ': Temperature: ' + body.main.temp + ' deg C.');
	}
});

Hi Andrew, I've done the stand alone node.js programs where you can obtain URL data , they work.
I am trying to go through the model answer you gave us in the callback section.

I have managed to get the file 'learningLocation.js' to work and that also works when called from file 'appLearningMA.js'
I then moved onto file 'learningWeather.js' - this doesn't work.
I typed in code similar to that for 'learningLocation.js', and it fails.
I created a standalone file for 'learningWeather.js' and that works, the object can be read.
So now, I don't understand, why 'learningWeather.js' fails to work when I try to run call it from 'appLearningMA.js'

Also, what can I do to be able to debug this by myself without having to resort to asking you about this type of problem in future? Thanks

Hey,

The best way to debug this would be to following the execution of the application. On line 14 of appLearningMA.js the problem is not with the function that's called. The problem is with that first argument, location.

On line 14 the location function is getting passed in, not a string location like userLocation. That's why the program is crashing.

- Andrew