Basic Operations

react native crud tutorial introduction storing data on parse is built around parse object parse object class each parse object parse object contains key value pairs of json compatible data this data is schemaless, which means that you don’t need to specify ahead of time what keys exist on each parse object parse object you can simply set whatever key value pairs you want, and our backend will store it you can also specify the datatypes according to your application needs and persist types such as number number , boolean boolean , string string , datetime datetime , list list , geopointers geopointers , and object object , encoding them to json before saving parse also supports store and query relational data by using the types pointers pointers and relations relations in this guide, you will learn how to perform basic data operations through a crud example app, which will show you how to create, read, update and delete data from your parse server database in react native you will first create your component functions for each crud operation, using them later in a complete screen layout, resulting in a to do list app prerequisites to complete this tutorial, you will need a react native app created and connected to back4app if you want to test/use the screen layout provided by this guide, you should set up the react native paper react native paper library goal to build a basic crud application in react native using parse 1 creating data objects the first step to manage your data in your parse database is to have some on it let’s now make a createtodo createtodo function that will create a new instance of parse object parse object with the “todo” subclass the todo will have a title( string string ) describing the task and a done( boolean boolean ) field indicating if the task is completed javascript 1 const createtodo = async function () { 2 // this value comes from a state variable 3 const newtodotitlevalue = newtodotitle; 4 // creates a new todo parse object instance 5 let todo = new parse object('todo'); 6 todo set('title', newtodotitlevalue); 7 todo set('done', false); 8 // after setting the todo values, save it on the server 9 try { 10 await todo save(); 11 // success 12 alert alert('success!', 'todo created!'); 13 // refresh todos list to show the new one (you will create this function later) 14 readtodos(); 15 return true; 16 } catch (error) { 17 // error can be caused by lack of internet connection 18 alert alert('error!', error message); 19 return false; 20 }; 21 }; todolist tsx 1 const createtodo = async function () promise\<boolean> { 2 // this value comes from a state variable 3 const newtodotitlevalue string = newtodotitle; 4 // creates a new todo parse object instance 5 let todo parse object = new parse object('todo'); 6 todo set('title', newtodotitlevalue); 7 todo set('done', false); 8 // after setting the todo values, save it on the server 9 try { 10 await todo save(); 11 // success 12 alert alert('success!', 'todo created!'); 13 // refresh todos list to show the new one (you will create this function later) 14 readtodos(); 15 return true; 16 } catch (error) { 17 // error can be caused by lack of internet connection 18 alert alert('error!', error message); 19 return false; 20 }; 21 }; notice that if your database does not have a todo todo table (or subclass) in it yet, parse will create it automatically and also add any columns set inside the parse object parse object instance using the parse object set() parse object set() method, which takes two arguments the field name and the value to be set 2 reading data objects after creating some data in your database, your application can now be able to read it from the server and show it to your user go ahead and create a readtodos readtodos function, which will perform a parse query parse query , storing the result inside a state variable javascript 1 const readtodos = async function () { 2 // reading parse objects is done by using parse query 3 const parsequery = new parse query('todo'); 4 try { 5 let todos = await parsequery find(); 6 // be aware that empty or invalid queries return as an empty array 7 // set results to state variable 8 setreadresults(todos); 9 return true; 10 } catch (error) { 11 // error can be caused by lack of internet connection 12 alert alert('error!', error message); 13 return false; 14 }; 15 };1 const readtodos = async function () promise\<boolean> { 2 // reading parse objects is done by using parse query 3 const parsequery parse query = new parse query('todo'); 4 try { 5 let todos parse object\[] = await parsequery find(); 6 // be aware that empty or invalid queries return as an empty array 7 // set results to state variable 8 setreadresults(todos); 9 return true; 10 } catch (error) { 11 // error can be caused by lack of internet connection 12 alert alert('error!', error message); 13 return false; 14 }; 15 }; the parse query parse query class is very powefull, many constraints and orderings can be applied to your queries for now, we will stick to this simple query, which will retrieve every saved todo todo object 3 updating data objects updating a parse object parse object instance is very similar to creating a new one, except that in this case, you need to assign the previously created objectid objectid to it and then save, after setting your new values javascript 1 const updatetodo = async function (todoid, done) { 2 // create a new todo parse object instance and set todo id 3 let todo = new parse object('todo'); 4 todo set('objectid', todoid); 5 // set new done value and save parse object changes 6 todo set('done', done); 7 try { 8 await todo save(); 9 // success 10 alert alert('success!', 'todo updated!'); 11 // refresh todos list 12 readtodos(); 13 return true; 14 } catch (error) { 15 // error can be caused by lack of internet connection 16 alert alert('error!', error message); 17 return false; 18 }; 19 };1 const updatetodo = async function ( 2 todoid string, 3 done boolean, 4 ) promise\<boolean> { 5 // create a new todo parse object instance and set todo id 6 let todo parse object = new parse object('todo'); 7 todo set('objectid', todoid); 8 // set new done value and save parse object changes 9 todo set('done', done); 10 try { 11 await todo save(); 12 // success 13 alert alert('success!', 'todo updated!'); 14 // refresh todos list 15 readtodos(); 16 return true; 17 } catch (error) { 18 // error can be caused by lack of internet connection 19 alert alert('error!', error message); 20 return false; 21 }; 22 }; since this example app represents a to do list, your update function takes an additional argument, the done done value, which will represent if the specific task is completed or not 4 deleting data objects to delete a data object, you need to call the destroy() destroy() method in the parse object parse object instance representing it please be careful because this operation is not reversible javascript 1 const deletetodo = async function (todoid) { 2 // create a new todo parse object instance and set todo id 3 const todo = new parse object('todo'); 4 todo set('objectid', todoid); 5 // destroy should be called to delete a parse object 6 try { 7 await todo destroy(); 8 alert alert('success!', 'todo deleted!'); 9 // refresh todos list to remove this one 10 readtodos(); 11 return true; 12 } catch (error) { 13 // error can be caused by lack of internet connection 14 alert alert('error!', error message); 15 return false; 16 }; 17 };1 const deletetodo = async function (todoid string) promise\<boolean> { 2 // create a new todo parse object instance and set todo id 3 let todo parse object = new parse object('todo'); 4 todo set('objectid', todoid); 5 // destroy should be called to delete a parse object 6 try { 7 await todo destroy(); 8 alert alert('success!', 'todo deleted!'); 9 // refresh todos list to remove this one 10 readtodos(); 11 return true; 12 } catch (error) { 13 // error can be caused by lack of internet connection 14 alert alert('error!', error message); 15 return false; 16 }; 17 }; let´s now use these four functions in a complete component, so you can test it and make sure that every crud operation is working properly 5 using crud in a react native component here is the complete component code, including styled user interface elements, state variables, and calls to your crud functions you can create a separate component in a file called todolist js/todolist tsx todolist js/todolist tsx containing the following code or add it to your main application file ( app js/app tsx app js/app tsx or index js index js ) todolist js 1 import react, {usestate} from 'react'; 2 import { 3 alert, 4 view, 5 safeareaview, 6 image, 7 scrollview, 8 statusbar, 9 stylesheet, 10 touchableopacity, 11 } from 'react native'; 12 import parse from 'parse/react native'; 13 import { 14 list, 15 title, 16 iconbutton, 17 text as papertext, 18 button as paperbutton, 19 textinput as papertextinput, 20 } from 'react native paper'; 21&#x9; 22 export const todolist = () => { 23 // state variables 24 const \[readresults, setreadresults] = usestate(\[]); 25 const \[newtodotitle, setnewtodotitle] = usestate(''); 26&#x9; 27 // functions used by the screen components 28 const createtodo = async function () { 29 // this value comes from a state variable 30 const newtodotitlevalue = newtodotitle; 31 // creates a new todo parse object instance 32 let todo = new parse object('todo'); 33 todo set('title', newtodotitlevalue); 34 todo set('done', false); 35 // after setting the todo values, save it on the server 36 try { 37 await todo save(); 38 // success 39 alert alert('success!', 'todo created!'); 40 // refresh todos list to show the new one (you will create this function later) 41 readtodos(); 42 return true; 43 } catch (error) { 44 // error can be caused by lack of internet connection 45 alert alert('error!', error message); 46 return false; 47 } 48 }; 49&#x9; 50 const readtodos = async function () { 51 // reading parse objects is done by using parse query 52 const parsequery = new parse query('todo'); 53 try { 54 let todos = await parsequery find(); 55 // be aware that empty or invalid queries return as an empty array 56 // set results to state variable 57 setreadresults(todos); 58 return true; 59 } catch (error) { 60 // error can be caused by lack of internet connection 61 alert alert('error!', error message); 62 return false; 63 } 64 }; 65&#x9; 66 const updatetodo = async function (todoid, done) { 67 // create a new todo parse object instance and set todo id 68 let todo = new parse object('todo'); 69 todo set('objectid', todoid); 70 // set new done value and save parse object changes 71 todo set('done', done); 72 try { 73 await todo save(); 74 // success 75 alert alert('success!', 'todo updated!'); 76 // refresh todos list 77 readtodos(); 78 return true; 79 } catch (error) { 80 // error can be caused by lack of internet connection 81 alert alert('error!', error message); 82 return false; 83 }; 84 }; 85&#x9; 86 const deletetodo = async function (todoid) { 87 // create a new todo parse object instance and set todo id 88 let todo = new parse object('todo'); 89 todo set('objectid', todoid); 90 // destroy should be called to delete a parse object 91 try { 92 await todo destroy(); 93 alert alert('success!', 'todo deleted!'); 94 // refresh todos list to remove this one 95 readtodos(); 96 return true; 97 } catch (error) { 98 // error can be caused by lack of internet connection 99 alert alert('error!', error message); 100 return false; 101 } 102 }; 103&#x9; 104 return ( 105 <> 106 \<statusbar backgroundcolor="#208aec" /> 107 \<safeareaview style={styles container}> 108 \<view style={styles header}> 109 \<image 110 style={styles header logo} 111 source={ { 112 uri 113 'https //blog back4app com/wp content/uploads/2019/05/back4app white logo 500px png', 114 } } 115 /> 116 \<papertext style={styles header text bold}> 117 {'react native on back4app'} 118 \</papertext> 119 \<papertext style={styles header text}>{'product creation'}\</papertext> 120 \</view> 121 \<view style={styles wrapper}> 122 \<view style={styles flex between}> 123 \<title>todo list\</title> 124 {/ todo read (refresh) button /} 125 \<iconbutton 126 icon="refresh" 127 color={'#208aec'} 128 size={24} 129 onpress={() => readtodos()} 130 /> 131 \</view> 132 \<view style={styles create todo container}> 133 {/ todo create text input /} 134 \<papertextinput 135 value={newtodotitle} 136 onchangetext={text => setnewtodotitle(text)} 137 label="new todo" 138 mode="outlined" 139 style={styles create todo input} 140 /> 141 {/ todo create button /} 142 \<paperbutton 143 onpress={() => createtodo()} 144 mode="contained" 145 icon="plus" 146 color={'#208aec'} 147 style={styles create todo button}> 148 {'add'} 149 \</paperbutton> 150 \</view> 151 \<scrollview> 152 {/ todo read results list /} 153 {readresults !== null && 154 readresults !== undefined && 155 readresults map((todo) => ( 156 \<list item 157 key={todo id} 158 title={todo get('title')} 159 titlestyle={ 160 todo get('done') === true 161 ? styles todo text done 162 styles todo text 163 } 164 style={styles todo item} 165 right={props => ( 166 <> 167 {/ todo update button /} 168 {todo get('done') !== true && ( 169 \<touchableopacity 170 onpress={() => updatetodo(todo id, true)}> 171 \<list icon 172 { props} 173 icon="check" 174 color={'#4caf50'} 175 /> 176 \</touchableopacity> 177 )} 178 {/ todo delete button /} 179 \<touchableopacity onpress={() => deletetodo(todo id)}> 180 \<list icon { props} icon="close" color={'#ef5350'} /> 181 \</touchableopacity> 182 \</> 183 )} 184 /> 185 ))} 186 \</scrollview> 187 \</view> 188 \</safeareaview> 189 \</> 190 ); 191 }; 192&#x9; 193 // these define the screen component styles 194 const styles = stylesheet create({ 195 container { 196 flex 1, 197 backgroundcolor '#fff', 198 }, 199 wrapper { 200 width '90%', 201 alignself 'center', 202 }, 203 header { 204 alignitems 'center', 205 paddingtop 10, 206 paddingbottom 20, 207 backgroundcolor '#208aec', 208 }, 209 header logo { 210 width 170, 211 height 40, 212 marginbottom 10, 213 resizemode 'contain', 214 }, 215 header text bold { 216 color '#fff', 217 fontsize 14, 218 fontweight 'bold', 219 }, 220 header text { 221 margintop 3, 222 color '#fff', 223 fontsize 14, 224 }, 225 flex between { 226 flexdirection 'row', 227 alignitems 'center', 228 justifycontent 'space between', 229 }, 230 create todo container { 231 flexdirection 'row', 232 }, 233 create todo input { 234 flex 1, 235 height 38, 236 marginbottom 16, 237 backgroundcolor '#fff', 238 fontsize 14, 239 }, 240 create todo button { 241 margintop 6, 242 marginleft 15, 243 height 40, 244 }, 245 todo item { 246 borderbottomwidth 1, 247 borderbottomcolor 'rgba(0, 0, 0, 0 12)', 248 }, 249 todo text { 250 fontsize 15, 251 }, 252 todo text done { 253 color 'rgba(0, 0, 0, 0 3)', 254 fontsize 15, 255 textdecorationline 'line through', 256 }, 257 }) todolist tsx 1 import react, {fc, reactelement, usestate} from 'react'; 2 import { 3 alert, 4 view, 5 safeareaview, 6 image, 7 scrollview, 8 statusbar, 9 stylesheet, 10 touchableopacity, 11 } from 'react native'; 12 import parse from 'parse/react native'; 13 import { 14 list, 15 title, 16 iconbutton, 17 text as papertext, 18 button as paperbutton, 19 textinput as papertextinput, 20 } from 'react native paper'; 21&#x9; 22 export const todolist fc<{}> = ({}) reactelement => { 23 // state variables 24 const \[readresults, setreadresults] = usestate<\[parse object]>(); 25 const \[newtodotitle, setnewtodotitle] = usestate(''); 26&#x9; 27 // functions used by the screen components 28 const createtodo = async function () promise\<boolean> { 29 // this value comes from a state variable 30 const newtodotitlevalue string = newtodotitle; 31 // creates a new todo parse object instance 32 let todo parse object = new parse object('todo'); 33 todo set('title', newtodotitlevalue); 34 todo set('done', false); 35 // after setting the todo values, save it on the server 36 try { 37 await todo save(); 38 // success 39 alert alert('success!', 'todo created!'); 40 // refresh todos list to show the new one (you will create this function later) 41 readtodos(); 42 return true; 43 } catch (error) { 44 // error can be caused by lack of internet connection 45 alert alert('error!', error message); 46 return false; 47 } 48 }; 49&#x9; 50 const readtodos = async function () promise\<boolean> { 51 // reading parse objects is done by using parse query 52 const parsequery parse query = new parse query('todo'); 53 try { 54 let todos parse object\[] = await parsequery find(); 55 // be aware that empty or invalid queries return as an empty array 56 // set results to state variable 57 setreadresults(todos); 58 return true; 59 } catch (error) { 60 // error can be caused by lack of internet connection 61 alert alert('error!', error message); 62 return false; 63 } 64 }; 65&#x9; 66 const updatetodo = async function ( 67 todoid string, 68 done boolean, 69 ) promise\<boolean> { 70 // create a new todo parse object instance and set todo id 71 let todo parse object = new parse object('todo'); 72 todo set('objectid', todoid); 73 // set new done value and save parse object changes 74 todo set('done', done); 75 try { 76 await todo save(); 77 // success 78 alert alert('success!', 'todo updated!'); 79 // refresh todos list 80 readtodos(); 81 return true; 82 } catch (error) { 83 // error can be caused by lack of internet connection 84 alert alert('error!', error message); 85 return false; 86 } 87 }; 88&#x9; 89 const deletetodo = async function (todoid string) promise\<boolean> { 90 // create a new todo parse object instance and set todo id 91 let todo parse object = new parse object('todo'); 92 todo set('objectid', todoid); 93 // destroy should be called to delete a parse object 94 try { 95 await todo destroy(); 96 alert alert('success!', 'todo deleted!'); 97 // refresh todos list to remove this one 98 readtodos(); 99 return true; 100 } catch (error) { 101 // error can be caused by lack of internet connection 102 alert alert('error!', error message); 103 return false; 104 } 105 }; 106&#x9; 107 return ( 108 <> 109 \<statusbar backgroundcolor="#208aec" /> 110 \<safeareaview style={styles container}> 111 \<view style={styles header}> 112 \<image 113 style={styles header logo} 114 source={ { 115 uri 116 'https //blog back4app com/wp content/uploads/2019/05/back4app white logo 500px png', 117 } } 118 /> 119 \<papertext style={styles header text bold}> 120 {'react native on back4app'} 121 \</papertext> 122 \<papertext style={styles header text}>{'product creation'}\</papertext> 123 \</view> 124 \<view style={styles wrapper}> 125 \<view style={styles flex between}> 126 \<title>todo list\</title> 127 {/ todo read (refresh) button /} 128 \<iconbutton 129 icon="refresh" 130 color={'#208aec'} 131 size={24} 132 onpress={() => readtodos()} 133 /> 134 \</view> 135 \<view style={styles create todo container}> 136 {/ todo create text input /} 137 \<papertextinput 138 value={newtodotitle} 139 onchangetext={text => setnewtodotitle(text)} 140 label="new todo" 141 mode="outlined" 142 style={styles create todo input} 143 /> 144 {/ todo create button /} 145 \<paperbutton 146 onpress={() => createtodo()} 147 mode="contained" 148 icon="plus" 149 color={'#208aec'} 150 style={styles create todo button}> 151 {'add'} 152 \</paperbutton> 153 \</view> 154 \<scrollview> 155 {/ todo read results list /} 156 {readresults !== null && 157 readresults !== undefined && 158 readresults map((todo parse object) => ( 159 \<list item 160 key={todo id} 161 title={todo get('title')} 162 titlestyle={ 163 todo get('done') === true 164 ? styles todo text done 165 styles todo text 166 } 167 style={styles todo item} 168 right={props => ( 169 <> 170 {/ todo update button /} 171 {todo get('done') !== true && ( 172 \<touchableopacity 173 onpress={() => updatetodo(todo id, true)}> 174 \<list icon 175 { props} 176 icon="check" 177 color={'#4caf50'} 178 /> 179 \</touchableopacity> 180 )} 181 {/ todo delete button /} 182 \<touchableopacity onpress={() => deletetodo(todo id)}> 183 \<list icon { props} icon="close" color={'#ef5350'} /> 184 \</touchableopacity> 185 \</> 186 )} 187 /> 188 ))} 189 \</scrollview> 190 \</view> 191 \</safeareaview> 192 \</> 193 ); 194 }; 195&#x9; 196 // these define the screen component styles 197 const styles = stylesheet create({ 198 container { 199 flex 1, 200 backgroundcolor '#fff', 201 }, 202 wrapper { 203 width '90%', 204 alignself 'center', 205 }, 206 header { 207 alignitems 'center', 208 paddingtop 10, 209 paddingbottom 20, 210 backgroundcolor '#208aec', 211 }, 212 header logo { 213 width 170, 214 height 40, 215 marginbottom 10, 216 resizemode 'contain', 217 }, 218 header text bold { 219 color '#fff', 220 fontsize 14, 221 fontweight 'bold', 222 }, 223 header text { 224 margintop 3, 225 color '#fff', 226 fontsize 14, 227 }, 228 flex between { 229 flexdirection 'row', 230 alignitems 'center', 231 justifycontent 'space between', 232 }, 233 create todo container { 234 flexdirection 'row', 235 }, 236 create todo input { 237 flex 1, 238 height 38, 239 marginbottom 16, 240 backgroundcolor '#fff', 241 fontsize 14, 242 }, 243 create todo button { 244 margintop 6, 245 marginleft 15, 246 height 40, 247 }, 248 todo item { 249 borderbottomwidth 1, 250 borderbottomcolor 'rgba(0, 0, 0, 0 12)', 251 }, 252 todo text { 253 fontsize 15, 254 }, 255 todo text done { 256 color 'rgba(0, 0, 0, 0 3)', 257 fontsize 15, 258 textdecorationline 'line through', if your component is properly set up, you should see something like this after building and running the app go ahead and add some to do’s by typing its titles in the input box one at a time and pressing on the add add button note that after every successful creation, the createtodo createtodo function triggers the readtodos readtodos one, refreshing your task list automatically you should now have a sizeable to do list like this you can now mark your tasks as done by clicking in the checkmark beside it, causing their done done value to be updated to true and changing its icon status on the left the only remaining data operation is now the delete one, which can be done by pressing on the trash can icon at the far right of your to do list object after successfully deleting an object, you should get an alert message like this conclusion at the end of this guide, you learned how to perform basic data operations (crud) in parse on react native in the next guide, we will show you which data types are supported in parse and how to use them