管理同步订阅 - React Native SDK

import React, {useEffect, useState} from 'react';
import {useRealm, useQuery} from '@realm/react';
import {View, Text, FlatList} from 'react-native';
import {Bird} from '../../models';
import {Subscription} from 'realm/dist/bundle';
export const BasicSubscription = () => {
  const realm = useRealm();
  // Get all local birds that have not been seen yet.
  const seenBirds = useQuery(Bird, collection =>
    collection.filtered('haveSeen == true'),
  );
  const [seenBirdsSubscription, setSeenBirdsSubscription] =
    useState<Subscription | null>();
  useEffect(() => {
    // Create an async function so that we can `await` the
    // promise from `.subscribe()`.
    const createSubscription = async () => {
      await seenBirds.subscribe({
        name: 'Birds I have seen',
      });
    };
    createSubscription().catch(console.error);
    // Get the subscription...
    const subscription = realm.subscriptions.findByName('Birds I have seen');
    // ... and set it to a stateful variable or manage it in `useEffect`.
    setSeenBirdsSubscription(subscription);
  }, []);
  return (
    // Work with the subscribed results list or modify the subscription...
    <></>
  );
};

import React, {useEffect, useState} from 'react';
import {BSON, WaitForSync} from 'realm';
import {useRealm, useQuery} from '@realm/react';
import {View, Text, Button, TextInput, FlatList} from 'react-native';
import {Bird} from '../../models';
import {Subscription} from 'realm/dist/bundle';
export const WaitFirstTime = () => {
  const realm = useRealm();
  const [birdName, setBirdName] = useState('Change me!');
  // Get local birds that have been marked as "haveSeen".
  const seenBirds = useQuery(Bird, collection =>
    collection.filtered('haveSeen == true'),
  );
  const [seenBirdsSubscription, setSeenBirdsSubscription] =
    useState<Subscription | null>();
  useEffect(() => {
    const createSubscription = async () => {
      // Only wait for sync to finish on the initial sync.
      await seenBirds.subscribe({
        behavior: WaitForSync.FirstTime,
        name: 'First time sync only',
      });
    };
    createSubscription().catch(console.error);
    // Get the subscription...
    const subscription = realm.subscriptions.findByName('First time sync only');
    // ... and set it to a stateful variable or manage it in `useEffect`.
    setSeenBirdsSubscription(subscription);
  }, []);
  return (
    // Work with the subscribed results list or modify the subscription...
    <></>
  );
};

export const AlwaysWait = () => {
  const realm = useRealm();
  // Get all local birds that have not been seen yet.
  const unSeenBirds = useQuery(Bird, collection =>
    collection.filtered('haveSeen == false'),
  );
  const [unSeenBirdsSubscription, setUnseenBirdsSubscription] =
    useState<Subscription | null>();
  useEffect(() => {
    const createSubscription = async () => {
      // Add subscription with timeout.
      // If timeout expires before sync is completed, currently-downloaded
      // objects are returned and sync download continues in the background.
      await unSeenBirds.subscribe({
        behavior: WaitForSync.Always,
        name: 'Always wait',
        timeout: 500,
      });
    };
    createSubscription().catch(console.error);
    // Get the subscription...
    const subscription = realm.subscriptions.findByName('Always wait');
    // ... and set it to a stateful variable or manage it in `useEffect`.
    setUnseenBirdsSubscription(subscription);
  }, []);
  return (
    // Work with the subscribed results list or modify the subscription...
    <></>
  );
};

import React, {useEffect, useState} from 'react';
import {useRealm, useQuery} from '@realm/react';
import {View, Text, Button} from 'react-native';
import {Bird} from '../../models';
import {Subscription} from 'realm/dist/bundle';
export const Unsubscribe = () => {
  const realm = useRealm();
  const birds = useQuery(Bird);
  const unsubscribeFromQuery = () => {
    birds.unsubscribe();
  };
  return (
    <View>
      <Button
        title="Unsubscribe"
        onPress={() => {
          unsubscribeFromQuery();
        }}
      />
    </View>
  );
};

import React, {useEffect, useState} from 'react';
import {Text, FlatList} from 'react-native';
import {useRealm, useQuery} from '@realm/react';
import {Bird} from '../Models/Bird';
function SubscriptionManager() {
  const realm = useRealm();
  // Pass object model to useQuery and filter results.
  // This does not create a subscription.
  const seenBirds = useQuery(Bird, birds => {
    return birds.filtered('haveSeen == true');
  });
  const [subscriptions, setSubcriptions] = useState<
    App.Sync.SubscriptionSet | undefined
  >();
  useEffect(() => {
    const createSubscription = async () => {
      // Create subscription for filtered results.
      await realm.subscriptions.update(mutableSubs => {
        mutableSubs.add(seenBirds, {name: 'seen birds'});
      });
    };
    createSubscription().catch(console.error);
    // Set to state variable.
    setSubcriptions(realm.subscriptions);
  }, []);
  return (
    <FlatList
      data={subscriptions}
      keyExtractor={subscription => subscription.id.toString()}
      renderItem={({item}) => <Text>{item.name}</Text>}
    />
  );
}

import React, {useEffect} from 'react';
import {Text, FlatList} from 'react-native';
import {useRealm, useQuery} from '@realm/react';
function SubscriptionManager() {
  const realm = useRealm();
  const seenBirds = useQuery(Bird, birds => {
    return birds.filtered('haveSeen == true');
  });
  useEffect(() => {
    realm.subscriptions.update(
      (mutableSubs: Realm.App.Sync.MutableSubscriptionSet) => {
        // Create subscription for filtered collection.
        mutableSubs.add(seenBirds, {name: 'seenBirds'});
      },
    );
  });
  return (
    <FlatList
      data={seenBirds}
      keyExtractor={item => item._id.toString()}
      renderItem={({item}) => <Text>{item._id.toString()}</Text>}
    />
  );
}

import React from 'react';
import {AppProvider, UserProvider} from '@realm/react';
// get realm context from createRealmContext()
import {RealmContext} from '../RealmConfig';
import {Text, FlatList} from 'react-native';
const {RealmProvider, useQuery} = RealmContext;
function AppWrapper() {
  return (
    <AppProvider id={APP_ID}>
      <UserProvider fallback={LogIn}>
        <RealmProvider
          sync={{
            flexible: true,
            initialSubscriptions: {
              update(subs, realm) {
                subs.add(realm.objects('Turtle'));
              },
            },
            onError: console.log,
          }}>
          <SubscriptionManager />
        </RealmProvider>
      </UserProvider>
    </AppProvider>
  );
}
function SubscriptionManager() {
  // Pass object model to useQuery to get all objects of type `Turtle`.
  // These results automatically update with changes from other devices
  // because we created a subscription with `initialSubscriptions`.
  const allTurtles = useQuery('Turtle');
  return (
    <FlatList
      data={allTurtles}
      keyExtractor={turtle => turtle._id.toString()}
      renderItem={({item}) => <Text>{item._id}</Text>}
    />
  );
}

import React, {useEffect} from 'react';
import {Text, View} from 'react-native';
import {useRealm, useQuery} from '@realm/react';
import {Bird} from '../Models/Bird';
function SubscriptionManager() {
  const realm = useRealm();
  const seenBirds = useQuery(Bird, birds => {
    return birds.filtered('haveSeen == true');
  });
  useEffect(() => {
    realm.subscriptions.update(
      (mutableSubs: Realm.App.Sync.MutableSubscriptionSet) => {
        // Create subscription for filtered collection.
        mutableSubs.add(seenBirds, {name: 'seenBirds'});
      },
    );
  });
  // Returns state of all subscriptions, not individual subscriptions.
  // In this case, it's just the subscription for `Bird` objects where
  // `haveSeen` is true.
  const allSubscriptionState = realm.subscriptions.state;
  return (
    <View>
      <Text >
        Status of all subscriptions: {allSubscriptionState}
      </Text>
    </View>
  );
}

realm.subscriptions.update((mutableSubs) => {
  mutableSubs.add(
    tasks.filtered('status == "completed" && progressMinutes > 180'),
    {
      name: "longRunningTasksSubscription",
    }
  );
});

import {useEffect} from 'react';
// get realm context from createRealmContext()
import {RealmContext} from '../RealmConfig';
const {useRealm} = RealmContext;
function SubscriptionManager() {
  const realm = useRealm();
  useEffect(() => {
    realm.subscriptions.update(mutableSubs => {
      // Remove subscription for object type `Turtle`,
      // which we added in `initialSubscriptions`.
      mutableSubs.removeByObjectType('Turtle');
    });
  });
  return (
    // ...
  );
}

// Query a constant list for a queryable field value
"priority IN { 1, 2, 3 }"

// Query an array-valued queryable field for a constant value
"'comedy' IN genres"