Pagination
Pagination example using Cloud Firestore.
Pagination using cloud firestore may be done in various ways but here's a basic way to do it using the firestore query features:
[orderBy, limit, startAfter]
Setup state
First, create a list display component with 2 state items; lastDocument and userData:
import React, { useState } from 'react';
import type { Node } from 'react';
import { Text, View, Button, Alert } from 'react-native';
import firestore from '@react-native-firebase/firestore';
const userCollection = firestore().collection('Users');
const App: () => Node = () => {
const [lastDocument, setLastDocument] = useState();
const [userData, setUserData] = useState([]);
};
LoadData function
Next, make a function called LoadData that fetches data from Users collection, and call it when a Button is pressed.
If lastDocument is not assigned (meaning initial load), the function will fetch from the start.
After successful fetch from the collection, store the last snapshot data by setLastDocument.
import React, { useState } from 'react';
import type { Node } from 'react';
import { Text, View, Button, Alert } from 'react-native';
import firestore from '@react-native-firebase/firestore';
const userCollection = firestore().collection('Users');
const App: () => Node = () => {
const [lastDocument, setLastDocument] = useState();
const [userData, setUserData] = useState([]);
function LoadData() {
console.log('LOAD');
let query = userCollection.orderBy('age'); // sort the data
if (lastDocument !== undefined) {
query = query..startAfter(lastDocument); // fetch data following the last document accessed
}
query.limit(3) // limit to your page size, 3 is just an example
.get()
.then(querySnapshot => {
setLastDocument(querySnapshot.docs[querySnapshot.docs.length - 1]);
MakeUserData(querySnapshot.docs);
});
}
}
return (
<View>
{userData}
<Button
onPress={() => {
LoadData();
}}
title="Load Next"
/>
</View>
);
};
MakeUserData function
This is just an example function, alter it to process the data to meet your requirements. In this specific example, it will replace the userData component with the new data fetched.
function MakeUserData(docs) {
let templist = []; //[...userData] <- use this instead of [] if you want to save the previous data.
docs.forEach((doc, i) => {
console.log(doc._data);
let temp = (
<View key={i} style={{ margin: 10 }}>
<Text>{doc._data.name}</Text>
<Text>{doc._data.age}</Text>
</View>
);
templist.push(temp);
});
setUserData(templist); //replace with the new data
}
Now, every time the button is pressed, Users collection data will be fetched one page at a time.
Conclusion
Here's the full example code
import React, { useState } from 'react';
import type { Node } from 'react';
import { Text, View, Button, Alert } from 'react-native';
import firestore from '@react-native-firebase/firestore';
const userCollection = firestore().collection('Users');
const App: () => Node = () => {
const [lastDocument, setLastDocument] = useState();
const [userData, setUserData] = useState([]);
function LoadData() {
console.log('LOAD');
let query = userCollection.orderBy('age'); // sort the data
if (lastDocument !== undefined) {
query = query..startAfter(lastDocument); // fetch data following the last document accessed
}
query.limit(3) // limit to your page size, 3 is just an example
.get()
.then(querySnapshot => {
setLastDocument(querySnapshot.docs[querySnapshot.docs.length - 1]);
MakeUserData(querySnapshot.docs);
});
}
}
function MakeUserData(docs) {
let templist = [];
docs.forEach((doc, i) => {
console.log(doc._data);
let temp = (
<View key={i} style={{ margin: 10 }}>
<Text>{doc._data.name}</Text>
<Text>{doc._data.age}</Text>
</View>
);
templist.push(temp);
});
setUserData(templist);
}
return (
<View>
{userData}
<Button
onPress={() => {
LoadData();
}}
title="Load Next"
/>
</View>
);
};
export default App;
