React Native Async Waiting in react native-sqlite-storage
I am little new to react to native. Before launching, I went through a lot of lessons. I am trying to make stores in my application that can be accessed by the screens of the application when required.
Here is my file structure.
- index.ios.js
- /app/index.js
- /app/store/database.js
- /app/store/userStore.js
index.ios.js
import { AppRegistry } from 'react-native';
import App from './app/index';
AppRegistry.registerComponent('AwesomeProject', () => App);
/app/index.js
import React, { Component} from 'react';
import {
Text,
View,
} from 'react-native';
import userStore from './store/userStore';
import ViewBackground from './components/ViewBackground';
class App extends Component {
constructor(props){
super(props);
this.isLoggedIn = true;
}
componentDidMount() {
this.fetchUsers().done();
}
async fetchUsers(){
console.log('Before User Fetch');
var result = await userStore.getAllUsers();
console.log('After User Fetch');
}
render() {
if(this.isLoggedIn){
return this.loggedInView();
}else{
return this.loggedOutView();
}
}
loggedInView(){
return <ViewBackground>
</ViewBackground>
}
loggedOutView(){
return <View>
<Text>Hi, This is logged Out view </Text>
</View>
}
}
export default App;
/app/store/userStore.js
import React from 'react'; import database from './database';
class UserStore{
async getAllUsers(){
let query = {
type: 'SELECT',
sql: 'SELECT * FROM Users',
vals: [],
}
let queries = [query];
console.log('in store before');
let dbResult = await database.runQuery(queries);
console.log('in store after');
return dbResult;
}
}
const userStore = new UserStore;
export default userStore;
/app/store/database.js
'use strict';
import React from 'react';
import SQLite from 'react-native-sqlite-storage';
SQLite.enablePromise(true);
var database_name = "test.db";
var database_version = "1.0";
var database_displayname = "Test";
var database_size = 1024 * 1024 * 10;
class Database {
constructor(){
SQLite.openDatabase(database_name, database_version, database_displayname, database_size).then(this.dbOpenSuccess).catch(this.dbOpenError);
}
dbOpenSuccess(dbInstance){
this.conn = dbInstance;
}
dbOpenError(err) {
}
getConnection() {
return this.conn;
}
setUpDatabase(){
let queries = [
'CREATE TABLE IF NOT EXISTS Users (user_id INTEGER PRIMARY KEY, f_name VARCHAR(64), l_name VARCHAR(64), email_id VARCHAR(128), mobile VARCHAR(10))'
];
this.conn.transaction( tx => {
queries.map( q => {
tx.executeSql(q, [], res => {}, err => {});
});
});
}
async runQuery(queries) {
await this.conn.transaction(tx => {
return Promise.all(queries.map(async (q) => {
try {
let results = null;
switch(q.type){
case 'SELECT':
results = await tx.executeSql(q.sql, q.vals);
console.log('Query', q, 'Executed. results:', results);
break;
}
} catch(err) {
console.log('Something went wrong while executing query', q, 'error is', err);
}
}));
});
return false;
}
closeDatabase(){
this.conn.close().then(this.dbCloseSuccess).catch(this.dbCloseError);
}
dbCloseSuccess(res) {
}
dbCloseError(err){
}
}
const dbInstance = new Database();
dbInstance.setUpDatabase();
export default dbInstance;
As you can see from the code that is in /app/index.js , I am trying to find users from userStore.js , which will finally call database.js to fetch users from the database. I want to pause code execution when I try to fetch users from the DB, so I tried using async / await.
If you can see in the code, I used console.log () to check if the execution is paused or in progress. None of the async / await works on any of the files. I am getting a response after the console.log completes .
I want to wait while I get data from DB. Please give some expert advice where I am wrong. Thanks in advance.
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You need to wrap it in a Promise and then resolve the result after sql is executed.
eg
async () => {
return new Promise((resolve, reject) => {
db.transaction(tx => {
tx.executeSql('SELECT * FROM users;', [], (tx, results) => {
const { rows } = results;
let users = [];
for (let i = 0; i < rows.length; i++) {
users.push({
...rows.item(i),
});
}
resolve(users);
});
});
});
}
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