ios - How to notify nearby users within a certain location -

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i've been thinking , couldn't figure out on how develop feature. app technically notify every driver, whenever user trigger button. i'm using google maps calculating routes , on.

the feature i'm building similar uber notification system, whenever user click "set pickup location" notify bunch of drivers nearby user's location.

but problem right now, notify every drivers online, , that's not want. want notify drivers nearby user's location.

how achieve this? sorts of variables need accomplish this

im using

  • ios/swift
  • google maps
  • node.js backend , socket.io realtime

algorithm overview

to notify user near you, suggest following algorithm:

  1. determine location
  2. determine location of other users
  3. calculate distance you

this algorithm simple, heavy, perhaps why @lu_ suggest on server.

optimizations

there multiple hacks optimize it, example, instead of checking location , calculating distance millions of users in app, can elect random subset, or can pick , choose more interesting based on criteria.

steps , code

the first , second steps of algorithm require find locations. effect suggest following example:

<!doctype html>  <html>    <head>    <title>geolocation</title>    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">    <meta charset="utf-8">    <style>      html,      body {        height: 100%;        margin: 0;        padding: 0;      }      #map {        height: 100%;      }    </style>  </head>    <body>    <div id="map"></div>    <script>      // note: example requires consent location sharing when       // prompted browser. if see error "the geolocation service       // failed.", means did not give permission browser       // locate you.        function initmap() {        var map = new google.maps.map(document.getelementbyid('map'), {          center: {            lat: -34.397,            lng: 150.644          },          zoom: 6        });        var infowindow = new google.maps.infowindow({          map: map        });          // try html5 geolocation.        if (navigator.geolocation) {          navigator.geolocation.getcurrentposition(function(position) {            var pos = {              lat: position.coords.latitude,              lng: position.coords.longitude            };              infowindow.setposition(pos);            infowindow.setcontent('location found.');            map.setcenter(pos);          }, function() {            handlelocationerror(true, infowindow, map.getcenter());          });        } else {          // browser doesn't support geolocation          handlelocationerror(false, infowindow, map.getcenter());        }      }        function handlelocationerror(browserhasgeolocation, infowindow, pos) {        infowindow.setposition(pos);        infowindow.setcontent(browserhasgeolocation ?          'error: geolocation service failed.' :          'error: browser doesn\'t support geolocation.');      }    </script>    <script async defer src="https://maps.googleapis.com/maps/api/js?callback=initmap">    </script>  </body>    </html>

please note need enable browser give location or website/service (i believe stackoverflow may block it, can check original example working on original page).

once have locations of , users want, can send information client or server. information can calculate distances original client, using information described in discussion calculate distance between 2 latitude-longitude points? (haversine formula) .

with distances, , location of original client, can decide do.


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