CODEWITHSUNDEEP
javascriptjqueryapicallbackgeolocation
dojs
dojs

Reputation: 517

Callback Hell, Geolocations - JavaScript

I am in Callback Hell, and I don't really get how I will get out of it. I've tried reading other topics that touch on the subject and I still don't grasp the concept.

I am working with the Google Maps API v3 and I am trying to return the users current position so I can keep passing it on to other methods.

I have managed to succeed by using the jQuery .done() out of context, it throws a warning but I manage to get my coordinate object.

If I call userPosition, how can I make that method wait for the findUser method before returning the variable userPosition?

Edit: Uploaded wrong code, and after edit, the indentation sucks. :)

userPosition: function(position)
            {
                 if (typeof position === 'undefined') 
                 {
                      //Call on findUser, when ready callback it self to set variables
                 } 
                 else 
                 {
                     //var userPosition = new google.maps.LatLng(position.coords.latitude, position.coords.longitude);
                     //return userPosition;
                 }
            },

findUser: function()
                {
                    var self = this;
                    if (navigator.geolocation)
                    {
                        navigator.geolocation.getCurrentPosition(
                            function(position) { // If successful
                                self.userPosition(position);
                            }, 
                            function(e) { // If something went wrong
                                var errors = {
                                    1: 'Permission denied',
                                    2: 'Position unavailable',
                                    3: 'Request timeout'
                                };
                                alert("Error: " + errors[e.code]);
                            },
                            { enableHighAccuracy: true, timeout: this.timeoutVal, maximumAge: 0 }
                        );
                    }
                    else
                    {
                        // Set flag
                    }
                },

Upvotes: 0

Views: 189

Answers (2)

Andy
Andy

Reputation: 63514

Here's how I've done it in this jsfiddle.

var thing = {

  findUser: function (callback) {
    var _this = this;

    // use the getPos method to get the geolocation
    this.getPos(function (position) {
        var lat, lng, userPos;
        lat = position.coords.latitude;
        lng = position.coords.longitude;

        // add the new lat lng to the userPosition variable
        _this.userPosition = new google.maps.LatLng(lat, lng);

        // invoke the callback
        callback();
    });
    return this;
  },

  getPos: function (callback) {
    var geo = navigator.geolocation;
    if (geo) {

        // get the geolocation and pass it back to findUser
        geo.getCurrentPosition(callback);
    }
    return this;
  }
}

// if userPosition doesn't exist then grab the geolocation
if (!thing.userPosition) {
  thing.findUser(function () {
    console.log(thing.userPosition);
  });
} else {
  console.log(thing.userPosition);
}

Upvotes: 2

Surender
Surender

Reputation: 757

var isUserLocationSet = false;
userPosition: function(position){

                if(!isUserLocationSet)
                {
                    settimeout(userPosition, 200);
                    return;
                }
                if (typeof position === 'undefined') 
                {
                    var userPosition = new google.maps.LatLng(position.coords.latitude, position.coords.longitude);
                    return userPosition;
                }
                console.log(typeof position);
            },

findUser: function(){
            //set isUserLocationSet to true on completion in this method
            var self = this;
            if (navigator.geolocation)
            {
                navigator.geolocation.getCurrentPosition(
                    function(position) { // If successful
                        self.userPosition(position);
                    }, 
                    function(e) { // If something went wrong
                        var errors = {
                            1: 'Permission denied',
                            2: 'Position unavailable',
                            3: 'Request timeout'
                        };
                        alert("Error: " + errors[e.code]);
                    },
                    { enableHighAccuracy: true, timeout: this.timeoutVal, maximumAge: 0 }
                );
            }
            else
            {
                // Set flag
            }
        }

Here you would check on the flag repetitively using settimeout and will keep calling the function until that flag is set.

Upvotes: 0

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