Geoqueries

using react geolocation to perform geoqueries with parse introduction in this guide, you will perform geoqueries in parse using the react geolocation you will implement a react component using these queries and learn how to set up and query realistic data using back4app and react prerequisites to complete this tutorial, you will need a react app created and connected to back4app if you want to run this guide’s example project, you should set up the ant design ant design library goal perform geoqueries using geopoints stored on back4app and react geolocation 1 understanding the parse query class any parse query operation uses the parse query parse query object type, which will help you retrieve specific data from your database throughout your app it is crucial to know that a parse query parse query will only resolve after calling a retrieve method (like parse query find parse query find or parse query get parse query get ), so a query can be set up and several modifiers can be chained before actually being called to create a new parse query parse query , you need to pass as a parameter the desired parse object parse object subclass, which is the one that will contain your query results an example query can be seen below, in which a fictional profile profile subclass is being queried 1 // this will create your query 2 let parsequery = new parse query("profile"); 3 // the query will resolve only after calling this method 4 let queryresult = await parsequery find(); you can read more about the parse query parse query class here at the official documentation https //parseplatform org/parse sdk js/api/master/parse query html 2 save some data on back4app let’s create a city city class, which will be the target of our queries in this guide on parse js console it is possible to run javascript code directly, querying and updating your application database contents using the js sdk commands run the code below from your js console and insert the data on back4app here is how the js console looks like in your dashboard go ahead and create the city city c class with the following example content 1 // add city objects and create table 2 // note how geopoints are created, passing latitude and longitude as arguments 3 // montevideo 4 var city = new parse object('city'); 5 city set('name', 'montevideo uruguay'); 6 city set('location', new parse geopoint( 34 85553195363169, 56 207280375137955)); 7 await city save(); 8&#x9; 9 // brasília 10 city = new parse object('city'); 11 city set('name', 'brasília brazil'); 12 city set('location', new parse geopoint( 15 79485821477289, 47 88391074690196)); 13 await city save(); 14&#x9; 15 // bogotá 16 city = new parse object('city'); 17 city set('name', 'bogotá colombia'); 18 city set('location', new parse geopoint(4 69139880891712, 74 06936691331047)); 19 await city save(); 20&#x9; 21 // mexico city 22 city = new parse object('city'); 23 city set('name', 'mexico city mexico'); 24 city set('location', new parse geopoint(19 400977162618933, 99 13311378164776)); 25 await city save(); 26&#x9; 27 // washington, d c 28 city = new parse object('city'); 29 city set('name', 'washington, d c usa'); 30 city set('location', new parse geopoint(38 930727220189944, 77 04626261880388)); 31 await city save(); 32&#x9; 33 // ottawa 34 city = new parse object('city'); 35 city set('name', 'ottawa canada'); 36 city set('location', new parse geopoint(45 41102167733425, 75 695414598736)); 37 await city save(); 38&#x9; 39 console log('success!'); 3 query the data now that you have a populated class, we can now perform some geopoint queries in it let’s begin by ordering city city results by the nearest from kingston in jamaica (latitude 18 01808695059913 and longitude 76 79894232253473), using the parse query near parse query near method 1 // create your query 2 let parsequery = new parse query('city'); 3&#x9; 4 // create our geopoint for the query 5 let kingstongeopoint = new parse geopoint(18 018086950599134, 76 79894232253473); 6&#x9; 7 // `near` will order results based on distance between the geopoint type field from the class and the geopoint argument 8 parsequery near('location', kingstongeopoint); 9&#x9; 10 // the query will resolve only after calling this method, retrieving 11 // an array of `parse objects` 12 let queryresults = await parsequery find(); 13&#x9; 14 // let's show the results 15 for (let result of queryresults) { 16 // you access `parse objects` attributes by using ` get` 17 console log(result get('name')); 18 }; let’s now query using the method parse query withinkilometers parse query withinkilometers , which will retrieve all results whose geopoint field is located within the max distance kingston will be used once again as a reference and the distance limit will be 3000 km 1 // create your query 2 let parsequery = new parse query('city'); 3&#x9; 4 // create our geopoint for the query 5 let kingstongeopoint = new parse geopoint(18 018086950599134, 76 79894232253473); 6&#x9; 7 // you can also use `withinmiles` and `withinradians` the same way, 8 // but with different measuring unities 9 parsequery withinkilometers('location', kingstongeopoint, 3000); 10&#x9; 11 // the query will resolve only after calling this method, retrieving 12 // an array of `parse objects` 13 let queryresults = await parsequery find(); 14&#x9; 15 // let's show the results 16 for (let result of queryresults) { 17 // you access `parse objects` attributes by using ` get` 18 console log(result get('name')); 19 }; another useful query method is parse query withinpolygon parse query withinpolygon , which will query results whose geopoint field value is within the specified polygon, composed of an array of geopoints (at least three) if the polygon path is open, it will be closed automatically by parse connecting the last and first points for this example, you will be using a simple polygon that roughly contains the south american continent, composed of 5 distant geopoints in the ocean 1 // create your query 2 let parsequery = new parse query('city'); 3&#x9; 4 // create our geopoint polygon for the query 5 let geopoint1 = new parse geopoint(15 822238344514378, 72 42845934415942); 6 let geopoint2 = new parse geopoint( 0 7433770196268968, 97 44765968406668); 7 let geopoint3 = new parse geopoint( 59 997149373299166, 76 52969196322749); 8 let geopoint4 = new parse geopoint( 9 488786415007201, 18 346101586021952); 9 let geopoint5 = new parse geopoint(15 414859532811047, 60 00625459569375); 10&#x9; 11 // note that the polygon is merely an array of geopoint objects and that the first and last are not connected, so parse connects them for you 12 parsequery withinpolygon('location', \[geopoint1, geopoint2, geopoint3, geopoint4, geopoint5]); 13&#x9; 14 // the query will resolve only after calling this method, retrieving 15 // an array of `parse objects` 16 let queryresults = await parsequery find(); 17&#x9; 18 // let's show the results 19 for (let result of queryresults) { 20 // you access `parse objects` attributes by using ` get` 21 console log(result get('name')); 22 }; 4 query from a react component let’s now use our example queries inside a component in react, with a simple interface having a list showing results and also 3 buttons for calling the queries the component also retrieves the device’s current location using the navigator geolocation navigator geolocation javascript api, so the queries will be using real data, provided that the user didn’t disabled location access in the browser this is how the component code is laid out, note the doquery doquery functions, containing the example code form before javascript 1 import react, { usestate } from 'react'; 2 import parse from 'parse/dist/parse min js'; 3 import ' /app css'; 4 import { button, divider } from 'antd'; 5 import { closeoutlined, searchoutlined } from '@ant design/icons'; 6&#x9; 7 export const querygeo = () => { 8 // state variable 9 const \[queryresults, setqueryresults] = usestate(); 10&#x9; 11 const doquerynear = async function () { 12 // check if geolocation api is available in the browser 13 if ('geolocation' in navigator) { 14 // get current location and create the geopoint for the query 15 navigator geolocation getcurrentposition( 16 async function (position) { 17 const currentposition = { 18 latitude position coords latitude, 19 longitude position coords longitude, 20 }; 21 // create our geopoint 22 let currentlocationgeopoint = new parse geopoint( 23 currentposition latitude, 24 currentposition longitude 25 ); 26&#x9; 27 // create our query 28 let parsequery = new parse query('city'); 29&#x9; 30 // `near` will order results based on distance between the geopoint type field from the class and the geopoint argument 31 parsequery near('location', currentlocationgeopoint); 32&#x9; 33 try { 34 let results = await parsequery find(); 35 // set query results to state variable 36 setqueryresults(results); 37 return true; 38 } catch (error) { 39 // error can be caused by lack of internet connection 40 alert(`error! ${error message}`); 41 } 42 }, 43 function ( error) { 44 alert( 45 'you need to allow geolocation to retrieve your location on the browser to test this if you are on an apple os, enable it on your system preferences ' 46 ); 47 } 48 ); 49 } else { 50 alert('geolocation services are not supported by your browser '); 51 } 52 return false; 53 }; 54&#x9; 55 const doquerywithinkilometers = async function () { 56 // check if geolocation api is available in the browser 57 if ('geolocation' in navigator) { 58 // get current location and create the geopoint for the query 59 navigator geolocation getcurrentposition( 60 async function (position) { 61 const currentposition = { 62 latitude position coords latitude, 63 longitude position coords longitude, 64 }; 65 // create our geopoint 66 let currentlocationgeopoint = new parse geopoint( 67 currentposition latitude, 68 currentposition longitude 69 ); 70&#x9; 71 // create our query 72 let parsequery = new parse query('city'); 73&#x9; 74 // you can also use `withinmiles` and `withinradians` the same way, 75 // but with different measuring unities 76 parsequery withinkilometers( 77 'location', 78 currentlocationgeopoint, 79 3000 80 ); 81&#x9; 82 try { 83 let results = await parsequery find(); 84 // set query results to state variable 85 setqueryresults(results); 86 } catch (error) { 87 // error can be caused by lack of internet connection 88 alert(`error! ${error message}`); 89 } 90 }, 91 function ( error) { 92 alert( 93 'you need to allow geolocation to retrieve your location on the browser to test this if you are on an apple os, enable it on your system preferences ' 94 ); 95 } 96 ); 97 } else { 98 alert('geolocation services are not supported by your browser '); 99 } 100 return false; 101 }; 102&#x9; 103 const doquerywithinpolygon = async function () { 104 // create our geopoint polygon points 105 let geopoint1 = new parse geopoint(15 822238344514378, 72 42845934415942); 106 let geopoint2 = new parse geopoint( 0 7433770196268968, 97 44765968406668); 107 let geopoint3 = new parse geopoint( 59 997149373299166, 76 52969196322749); 108 let geopoint4 = new parse geopoint( 9 488786415007201, 18 346101586021952); 109 let geopoint5 = new parse geopoint(15 414859532811047, 60 00625459569375); 110&#x9; 111 // create our query 112 let parsequery = new parse query('city'); 113&#x9; 114 // note that the polygon is merely an array of geopoint objects and that the first and 115 // last are not connected, so parse connects them for you 116 parsequery withinpolygon('location', \[ 117 geopoint1, 118 geopoint2, 119 geopoint3, 120 geopoint4, 121 geopoint5, 122 ]); 123&#x9; 124 try { 125 let results = await parsequery find(); 126 // set query results to state variable 127 setqueryresults(results); 128 } catch (error) { 129 // error can be caused by lack of internet connection 130 alert(`error! ${error}`); 131 return false; 132 } 133 return true; 134 }; 135&#x9; 136 const clearqueryresults = async function () { 137 setqueryresults(undefined); 138 return true; 139 }; 140&#x9; 141 return ( 142 \<div> 143 \<div classname="header"> 144 \<img 145 classname="header logo" 146 alt="back4app logo" 147 src={ 148 'https //blog back4app com/wp content/uploads/2019/05/back4app white logo 500px png' 149 } 150 /> 151 \<p classname="header text bold">{'react on back4app'}\</p> 152 \<p classname="header text">{'geopoint queries'}\</p> 153 \</div> 154 \<div classname="container"> 155 \<div classname="flex between"> 156 \<h2 classname="heading">{'query list'}\</h2> 157 \<div classname="flex"> 158 \<button 159 onclick={() => doquerynear()} 160 type="primary" 161 classname="heading button" 162 color={'#208aec'} 163 icon={\<searchoutlined />} 164 > 165 query near 166 \</button> 167 \<button 168 onclick={() => doquerywithinkilometers()} 169 type="primary" 170 classname="heading button" 171 color={'#208aec'} 172 icon={\<searchoutlined />} 173 > 174 query within km 175 \</button> 176 \<button 177 onclick={() => doquerywithinpolygon()} 178 type="primary" 179 classname="heading button" 180 color={'#208aec'} 181 icon={\<searchoutlined />} 182 > 183 query within polygon 184 \</button> 185 \<button 186 onclick={() => clearqueryresults()} 187 type="primary" 188 classname="heading button" 189 color={'#208aec'} 190 icon={\<closeoutlined />} 191 > 192 clear results 193 \</button> 194 \</div> 195 \</div> 196 \<divider /> 197 \<div classname="flex between"> 198 \<div classname="flex child"> 199 {/ query list /} 200 {queryresults !== undefined && 201 queryresults map((result, index) => ( 202 \<div classname="list item" key={`${index}`}> 203 \<p classname="list item title">{`${result get('name')}`}\</p> 204 \</div> 205 ))} 206 {queryresults !== undefined && queryresults length <= 0 ? ( 207 \<p>{'no results here!'}\</p> 208 ) null} 209 \</div> 210 \</div> 211 \</div> 212 \</div> 213 ); 214 }; typescript 1 import react, { usestate, fc, reactelement } from 'react'; 2 import ' /app css'; 3 import { button, divider } from 'antd'; 4 import { closeoutlined, searchoutlined } from '@ant design/icons'; 5 const parse = require('parse/dist/parse min js'); 6&#x9; 7 type locationobject = {latitude number, longitude number}; 8&#x9; 9 export const querygeo fc<{}> = () reactelement => { 10 // state variable 11 const \[queryresults, setqueryresults] = usestate\<parse object\[]>(); 12&#x9; 13 const doquerynear = async function () promise\<boolean> { 14 // check if geolocation api is available in the browser 15 if ("geolocation" in navigator) { 16 // get current location and create the geopoint for the query 17 navigator geolocation getcurrentposition(async function (position) { 18 const currentposition locationobject = { latitude position coords latitude, longitude position coords longitude }; 19 // create our geopoint 20 let currentlocationgeopoint parse geopoint = new parse geopoint( 21 currentposition latitude, 22 currentposition longitude, 23 ); 24&#x9; 25 // create our query 26 let parsequery parse query = new parse query('city'); 27&#x9; 28 // `near` will order results based on distance between the geopoint type field from the class and the geopoint argument 29 parsequery near('location', currentlocationgeopoint); 30&#x9; 31 try { 32 let results parse object\[] = await parsequery find(); 33 // set query results to state variable 34 setqueryresults(results); 35 return true; 36 } catch (error) { 37 // error can be caused by lack of internet connection 38 alert(`error! ${error message}`); 39 } 40 }, function ( error any) { 41 alert("you need to allow geolocation to retrieve your location on the browser to test this if you are on an apple os, enable it on your system preferences "); 42 }); 43 } else { 44 alert("geolocation services are not supported by your browser "); 45 } 46 return false; 47 }; 48&#x9; 49 const doquerywithinkilometers = async function () promise\<boolean> { 50 // check if geolocation api is available in the browser 51 if ("geolocation" in navigator) { 52 // get current location and create the geopoint for the query 53 navigator geolocation getcurrentposition(async function (position) { 54 const currentposition locationobject = { latitude position coords latitude, longitude position coords longitude }; 55 // create our geopoint 56 let currentlocationgeopoint parse geopoint = new parse geopoint( 57 currentposition latitude, 58 currentposition longitude, 59 ); 60&#x9; 61 // create our query 62 let parsequery parse query = new parse query('city'); 63&#x9; 64 // you can also use `withinmiles` and `withinradians` the same way, 65 // but with different measuring unities 66 parsequery withinkilometers('location', currentlocationgeopoint, 3000); 67&#x9; 68 try { 69 let results parse object\[] = await parsequery find(); 70 // set query results to state variable 71 setqueryresults(results); 72 } catch (error) { 73 // error can be caused by lack of internet connection 74 alert(`error! ${error message}`); 75 } 76 }, function ( error any) { 77 alert("you need to allow geolocation to retrieve your location on the browser to test this if you are on an apple os, enable it on your system preferences "); 78 }); 79 } else { 80 alert("geolocation services are not supported by your browser "); 81 } 82 return false; 83 }; 84&#x9; 85 const doquerywithinpolygon = async function () promise\<boolean> { 86 // create our geopoint polygon points 87 // in react typescript types ('@types/parse'), parse query withinpolygon expects 88 // an array of number arrays, so you need to change the declarations 89 let geopoint1 number\[] = \[ 90 7 242 845 934 415 940,00 91 15 822 238 344 514 300,00 92 ]; 93 let geopoint2 number\[] = \[ 94 9 744 765 968 406 660,00 95 0 7433770196268968, 96 ]; 97 let geopoint3 number\[] = \[ 98 7 652 969 196 322 740,00 99 59 997 149 373 299 100,00 100 ]; 101 let geopoint4 number\[] = \[ 102 18 346 101 586 021 900,00 103 9 488 786 415 007 200,00 104 ]; 105 let geopoint5 number\[] = \[ 106 6 000 625 459 569 370,00 107 15 414 859 532 811 000,00 108 ]; 109&#x9; 110 // create our query 111 let parsequery parse query = new parse query('city'); 112&#x9; 113 // note that the polygon is merely an array of geopoint objects and that the first and 114 // last are not connected, so parse connects them for you 115 parsequery withinpolygon('location', \[ 116 geopoint1, 117 geopoint2, 118 geopoint3, 119 geopoint4, 120 geopoint5, 121 ]); 122&#x9; 123 try { 124 let results parse object\[] = await parsequery find(); 125 // set query results to state variable 126 setqueryresults(results); 127 } catch (error) { 128 // error can be caused by lack of internet connection 129 alert(`error! ${error}`); 130 return false; 131 } 132 return true; 133 }; 134&#x9; 135 const clearqueryresults = async function () promise\<boolean> { 136 setqueryresults(undefined); 137 return true; 138 }; 139&#x9; 140 return ( 141 \<div> 142 \<div classname="header"> 143 \<img 144 classname="header logo" 145 alt="back4app logo" 146 src={ 147 'https //blog back4app com/wp content/uploads/2019/05/back4app white logo 500px png' 148 } 149 /> 150 \<p classname="header text bold">{'react on back4app'}\</p> 151 \<p classname="header text">{'geopoint queries'}\</p> 152 \</div> 153 \<div classname="container"> 154 \<div classname="flex between"> 155 \<h2 classname="heading">{'query list'}\</h2> 156 \<div classname="flex"> 157 \<button 158 onclick={() => doquerynear()} 159 type="primary" 160 classname="heading button" 161 color={'#208aec'} 162 icon={\<searchoutlined />} 163 > 164 query near 165 \</button> 166 \<button 167 onclick={() => doquerywithinkilometers()} 168 type="primary" 169 classname="heading button" 170 color={'#208aec'} 171 icon={\<searchoutlined />} 172 > 173 query within km 174 \</button> 175 \<button 176 onclick={() => doquerywithinpolygon()} 177 type="primary" 178 classname="heading button" 179 color={'#208aec'} 180 icon={\<searchoutlined />} 181 > 182 query within polygon 183 \</button> 184 \<button 185 onclick={() => clearqueryresults()} 186 type="primary" 187 classname="heading button" 188 color={'#208aec'} 189 icon={\<closeoutlined />} 190 > 191 clear results 192 \</button> 193 \</div> 194 \</div> 195 \<divider /> 196 \<div classname="flex between"> 197 \<div classname="flex child"> 198 {/ query list /} 199 {queryresults !== undefined && 200 queryresults map((result parse object, index number) => ( 201 \<div classname="list item" key={`${index}`}> 202 \<p classname="list item title">{`${result get('name')}`}\</p> 203 \</div> 204 ))} 205 {queryresults !== undefined && 206 queryresults length <= 0 ? ( 207 \<p>{'no results here!'}\</p> 208 ) null} 209 \</div> 210 \</div> 211 \</div> 212 \</div> 213 ); 214 }; also add these classes to you app css app css file to fully render the component layout app css 1 html { 2 box sizing border box; 3 outline none; 4 overflow auto; 5 } 6&#x9; 7 , 8 before, 9 after { 10 margin 0; 11 padding 0; 12 box sizing inherit; 13 } 14&#x9; 15 h1, 16 h2, 17 h3, 18 h4, 19 h5, 20 h6 { 21 margin 0; 22 font weight bold; 23 } 24&#x9; 25 p { 26 margin 0; 27 } 28&#x9; 29 body { 30 margin 0; 31 background color #fff; 32 } 33&#x9; 34 container { 35 width 100%; 36 max width 900px; 37 margin auto; 38 padding 20px 0; 39 text align left; 40 } 41&#x9; 42 header { 43 align items center; 44 padding 25px 0; 45 background color #208aec; 46 } 47&#x9; 48 header logo { 49 height 55px; 50 margin bottom 20px; 51 object fit contain; 52 } 53&#x9; 54 header text bold { 55 margin bottom 3px; 56 color rgba(255, 255, 255, 0 9); 57 font size 16px; 58 font weight bold; 59 } 60&#x9; 61 header text { 62 color rgba(255, 255, 255, 0 9); 63 font size 15px; 64 } 65&#x9; 66 heading { 67 font size 22px; 68 } 69&#x9; 70 flex { 71 display flex; 72 } 73&#x9; 74 flex between { 75 display flex; 76 justify content space between; 77 } 78&#x9; 79 flex child { 80 flex 0 0 45%; 81 } 82&#x9; 83 heading button { 84 margin left 12px; 85 } 86&#x9; 87 list item { 88 padding bottom 15px; 89 margin bottom 15px; 90 border bottom 1px solid rgba(0,0,0,0 06); 91 text align left; 92 } 93&#x9; 94 list item title { 95 color rgba(0,0,0,0 87); 96 font size 17px; 97 } this is how the component should look like after rendering and querying one of the query functions conclusion at the end of this guide, you learned how geopoint data queries work on parse and how to perform them on back4app from a react application in the next guide, you will check how to create and manage users in parse