react-native-storage    !npm version

This is a local storage wrapper for both react native apps (using AsyncStorage) and web apps (using localStorage). ES6 syntax, promise for async load, fully tested with jest.

查看中文文档请点击 README-CHN.md

Install

``
npm install react-native-storage
npm install @react-native-community/async-storage
`

or

`
yarn add react-native-storage
yarn add @react-native-community/async-storage
`

Link

`
react-native link @react-native-community/async-storage
`

Usage

$3

`js
import Storage from 'react-native-storage';
import AsyncStorage from '@react-native-community/async-storage';

const storage = new Storage({
// maximum capacity, default 1000
size: 1000,

// Use AsyncStorage for RN apps, or window.localStorage for web apps.
// If storageBackend is not set, data will be lost after reload.
storageBackend: AsyncStorage, // for web: window.localStorage

// expire time, default: 1 day (1000 3600 24 milliseconds).
// can be null, which means never expire.
defaultExpires: 1000 3600 24,

// cache data in the memory. default is true.
enableCache: true,

// if data was not found in storage or expired data was found,
// the corresponding sync method will be invoked returning
// the latest data.
sync: {
// we'll talk about the details later.
}
});

// I suggest you have one (and only one) storage instance in global scope.

// for web
// window.storage = storage;

// for react native
// global.storage = storage;
`

$3

`js
// Save something with key only. (using only a keyname but no id)
// This key should be unique. This is for data frequently used.
// The key and value pair is permanently stored unless you remove it yourself.
storage.save({
key: 'loginState', // Note: Do not use underscore("_") in key!
data: {
from: 'some other site',
userid: 'some userid',
token: 'some token'
},

// if expires not specified, the defaultExpires will be applied instead.
// if set to null, then it will never expire.
expires: 1000 * 3600
});

// load
storage
.load({
key: 'loginState',

// autoSync (default: true) means if data is not found or has expired,
// then invoke the corresponding sync method
autoSync: true,

// syncInBackground (default: true) means if data expired,
// return the outdated data first while invoking the sync method.
// If syncInBackground is set to false, and there is expired data,
// it will wait for the new data and return only after the sync completed.
// (This, of course, is slower)
syncInBackground: true,

// you can pass extra params to the sync method
// see sync example below
syncParams: {
extraFetchOptions: {
// blahblah
},
someFlag: true
}
})
.then(ret => {
// found data go to then()
console.log(ret.userid);
})
.catch(err => {
// any exception including data not found
// goes to catch()
console.warn(err.message);
switch (err.name) {
case 'NotFoundError':
// TODO;
break;
case 'ExpiredError':
// TODO
break;
}
});

// --------------------------------------------------

// Save something with key and id.
// "key-id" data size cannot surpass the size parameter you pass in the constructor.
// By default the 1001st data will overwrite the 1st data item.
// If you then load the 1st data, a catch(NotFoundError) or sync will be invoked.
var userA = {
name: 'A',
age: 20,
tags: ['geek', 'nerd', 'otaku']
};

storage.save({
key: 'user', // Note: Do not use underscore("_") in key!
id: '1001', // Note: Do not use underscore("_") in id!
data: userA,
expires: 1000 * 60
});

// load
storage
.load({
key: 'user',
id: '1001'
})
.then(ret => {
// found data goes to then()
console.log(ret.userid);
})
.catch(err => {
// any exception including data not found
// goes to catch()
console.warn(err.message);
switch (err.name) {
case 'NotFoundError':
// TODO;
break;
case 'ExpiredError':
// TODO
break;
}
});

// --------------------------------------------------

// get all ids for "key-id" data under a key,
// note: does not include "key-only" information (which has no ids)
storage.getIdsForKey('user').then(ids => {
console.log(ids);
});

// get all the "key-id" data under a key
// !! important: this does not include "key-only" data
storage.getAllDataForKey('user').then(users => {
console.log(users);
});

// clear all "key-id" data under a key
// !! important: "key-only" data is not cleared by this function
storage.clearMapForKey('user');

// --------------------------------------------------

// remove a single record
storage.remove({
key: 'lastPage'
});
storage.remove({
key: 'user',
id: '1001'
});

// clear map and remove all "key-id" data
// !! important: "key-only" data is not cleared, and is left intact
storage.clearMap();
`

$3

There are two ways to set the sync method.
You can pass the sync method in the constructor's parameter, as a function in an object,
or you can define it at any time as shown below:

`js
storage.sync = {
// The name of the sync method must be the same as the data's key name
// And the passed params will be an all-in-one object.
// You can return a value or a promise here
async user(params) {
let {
id,
syncParams: { extraFetchOptions, someFlag }
} = params;
const response = await fetch('user/?id=' + id, {
...extraFetchOptions
});
const responseText = await response.text();
console.log(user${id} sync resp: , responseText);
const json = JSON.parse(responseText);
if (json && json.user) {
storage.save({
key: 'user',
id,
data: json.user
});
if (someFlag) {
// do something for some custom flag
}
// return required data when succeed
return json.user;
} else {
// throw error when failed
throw new Error(error syncing user${id}));
}
}
};
`

In the following example the sync method is called, when you invoke storage.load:

`js
storage.load({
key: 'user',
id: '1002'
}).then(...)
`

If there is no user 1002 currently in storage, then storage.sync.user will be invoked to fetch and return the remote data.

$3

`js
// Load batch data with an array of storage.load parameters.
// It will invoke each key's sync method,
// and when all are complete will return all the data in an ordered array.
// The sync methods behave according to the syncInBackground setting: (default true)
// When set to true (the default), if timed out will return the current value
// while when set to false, will wait till the sync method completes

storage.getBatchData([
{ key: 'loginState' },
{ key: 'checkPoint', syncInBackground: false },
{ key: 'balance' },
{ key: 'user', id: '1009' }
])
.then(results => {
results.forEach(result => {
console.log(result);
})
})

// Load batch data with one key and an array of ids.
storage.getBatchDataWithIds({
key: 'user',
ids: ['1001', '1002', '1003']
})
.then( ... )
``

There is an important difference between the way these two methods perform:
getBatchData will invoke separate sync methods for each different key one after the other when the corresponding data is missing or not in sync. However, getBatchDataWithIds will collect a list of the missing data, pushing their ids to an array, and then pass the array to the single corresponding sync method once, reducing the number of requests, so you need to implement array query on the server side and handle the parameters of sync method properly. Note that the id parameter can be a single string or an array of strings.

#### You are welcome to ask any question in the issues page.

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