# react-native-async-storage-listener #

A wrapper around React Native's AsyncStorage with a listener. Multiple Channels are supported.
Can be used where redux is not available.

## Usage
````js

import StorageListener from react-native-async-storage-listener

//Demo classes for subscribe demonstration
class DemoOne {
    callback = (text:string)=> {
        console.log('CALLBACK CALLED FOR INSTANCE OF DemoOne:', text)
    }
    callbackSecond = (text:string)=> {
        console.log('SECOND CALLBACK CALLED FOR INSTANCE OF DemoOne:', text)
    }
}

class DemoTwo {
    callback = (text:string)=> {
        console.log('CALLBACK CALLED FOR INSTANCE OF DemoTwo:', text)
    }
}


const demoOne = new DemoOne();
const demoTwo = new DemoTwo();

//initiating channels by setting values
StorageListener.setItem("test value 1", "CHANNEL 1");
StorageListener.setItem("test value 2", "CHANNEL 2");

//get available channels for subscription
const channels = StorageListener.getChannels();


const response = StorageListener.addSubscriber(demoOne.callback, channels[0]);
// console.log(response)
// {  success: true, message: 'subscribed to channel', subscriber_id: 'a13151d6-1336-4096-933c-eb8e12cd0b10'}
// subscriber_id is required to remove the subscription 
 
StorageListener.addSubscriber(demoTwo.callback, channels[0]);
StorageListener.addSubscriber(demoOne.callbackSecond, channels[1]);
StorageListener.setItem("test value A", "CHANNEL 1");
StorageListener.setItem("test value A", "CHANNEL 2");
//callbacks will be called for any update

const remove = StorageListener.removeSubscriber(subscriber_id);
// console.log(remove)
// returns true if subscriber_id is a valid id

StorageListener.removeAllSubscribers();
// removes all subscribers
````

## API Reference

## setItem
Creates new channel or updates the value of an existing channel

**parameters**

`value:string` - The value to update with 

`channelKey:string` - new channel key or a existing channel key  

**returns**: `void`

## getItem
Get value of an existing channel

**parameters**

`channelKey:string` - existing channel key  

**returns**: `string`

## clearItem
Delete an existing channel. This will also remove all the subscribers subscribed to the item/channel without providing any notification to the subscribers.

**parameters**

`channelKey:string` - existing channel key  

**returns**: `void`

## getChannels
Get all available existing channels

**parameters**: none

**returns**: `Array<string>`

## addSubscriber
Add a new subscriber

**parameters**

`callback: (state:string)=>void` - callback function with void return 

`channelKey:string` - existing channel key that wish to subscribe 

**returns**: `{success: true, message: "subscribed to channel", subscriber_id: key} | {success:false , message: "channel not found. use an existing channel key"}`

## removeSubscriber
Remove a subscriber

**parameters**

`key:string` - _subscriber_id_ returned from addSubscriber response  

**returns**: `boolean`

## removeAllSubscribers
Remove all subscribers

**parameters**: none
 
**returns**: `void`