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AsyncStorage

AsyncStorage is an asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.

It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.

On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. On Android, AsyncStorage will use either RocksDB or SQLite based on what is available. This JS code is a facade that provides a clear JS API, real Error objects, and non-multi functions. Each method returns a Promise object.

Methods

Properties

Reference

Methods

getItem()

static getItem(key, callback?)

Fetches key and passes the result to callback, along with an Error if there is any. Returns a Promise object.

setItem()

static setItem(key, value, callback?)

Sets value for key and calls callback on completion, along with an Error if there is any. Returns a Promise object.

removeItem()

static removeItem(key, callback?)

Returns a Promise object.

mergeItem()

static mergeItem(key, value, callback?)

Merges existing value with input value, assuming they are stringified json. Returns a Promise object. Not supported by all native implementations.

Example:

let UID123_object = {
  name: 'Chris',
  age: 30,
  traits: { hair: 'brown', eyes: 'brown' }
};

// need only define what will be added or updated
let UID123_delta = {
  age: 31,
  traits: { eyes: 'blue', shoe_size: 10 }
};

AsyncStorage.setItem(
  store_key,
  JSON.stringify(UID123_object),
  () => {
    AsyncStorage.mergeItem(
      'UID123',
      JSON.stringify(UID123_delta),
      () => {
        AsyncStorage.getItem('UID123', (err, result) => {
          console.log(result);
          // => {'name':'Chris','age':31,'traits':{'shoe_size':10,'hair':'brown','eyes':'blue'}}
        });
      }
    );
  }
);

clear()

static clear(callback?)

Erases all AsyncStorage for all clients, libraries, etc. You probably don't want to call this - use removeItem or multiRemove to clear only your own keys instead. Returns a Promise object.

getAllKeys()

static getAllKeys(callback?)

Gets all keys known to the app, for all callers, libraries, etc. Returns a Promise object.

Example: see multiGet for example

flushGetRequests()

static flushGetRequests()

Flushes any pending requests using a single multiget

multiGet()

static multiGet(keys, callback?)

multiGet invokes callback with an array of key-value pair arrays that matches the input format of multiSet. Returns a Promise object.

multiGet(['k1', 'k2'], cb) -> cb([['k1', 'val1'], ['k2', 'val2']])

Example:

AsyncStorage.getAllKeys((err, keys) => {
  AsyncStorage.multiGet(keys, (err, stores) => {
    stores.map((result, i, store) => {
      // get at each store's key/value so you can work with it
      let key = store[i][0];
      let value = store[i][1];
    });
  });
});

multiSet()

static multiSet(keyValuePairs, callback?)

multiSet and multiMerge take arrays of key-value array pairs that match the output of multiGet, e.g. Returns a Promise object.

multiSet([['k1', 'val1'], ['k2', 'val2']], cb);

Example: see multiMerge for an example

multiRemove()

static multiRemove(keys, callback?)

Delete all the keys in the keys array. Returns a Promise object.

Example:

let keys = ['k1', 'k2'];
AsyncStorage.multiRemove(keys, (err) => {
  // keys k1 & k2 removed, if they existed
  // do most stuff after removal (if you want)
});

multiMerge()

static multiMerge(keyValuePairs, callback?)

Merges existing values with input values, assuming they are stringified json. Returns a Promise object.

Not supported by all native implementations.

Example:

// first user, initial values
let UID234_object = {
  name: 'Chris',
  age: 30,
  traits: { hair: 'brown', eyes: 'brown' }
};

// first user, delta values
let UID234_delta = {
  age: 31,
  traits: { eyes: 'blue', shoe_size: 10 }
};

// second user, initial values
let UID345_object = {
  name: 'Marge',
  age: 25,
  traits: { hair: 'blonde', eyes: 'blue' }
};

// second user, delta values
let UID345_delta = {
  age: 26,
  traits: { eyes: 'green', shoe_size: 6 }
};

let multi_set_pairs = [
  ['UID234', JSON.stringify(UID234_object)],
  ['UID345', JSON.stringify(UID345_object)]
];
let multi_merge_pairs = [
  ['UID234', JSON.stringify(UID234_delta)],
  ['UID345', JSON.stringify(UID345_delta)]
];

AsyncStorage.multiSet(multi_set_pairs, (err) => {
  AsyncStorage.multiMerge(multi_merge_pairs, (err) => {
    AsyncStorage.multiGet(['UID234', 'UID345'], (err, stores) => {
      stores.map((result, i, store) => {
        let key = store[i][0];
        let val = store[i][1];
        console.log(key, val);
        // => UID234 {"name":"Chris","age":31,"traits":{"shoe_size":10,"hair":"brown","eyes":"blue"}}
        // => UID345 {"name":"Marge","age":26,"traits":{"shoe_size":6,"hair":"blonde","eyes":"green"}}
      });
    });
  });
});

Properties

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