signalr-hub-client

A library that provides an easy way to define SignalR hubs on the front-end by a schema object containing the events and the actions.

Example

import { useCallback, useEffect } from 'react'
import { CustomType, defineHubObject, Optional } from 'signalr-hub-client'

export const UserHub = defineHubObject({
  // The name of the hub, this will be used to produce the hub url as
  // `/hubs/user`. It is also possible to set the hub url through
  // `hubUrl` property.
  name: 'user',

  // The events on the client-side (front-end), that will be called
  // from the server.
  //
  // The format is like: { [ eventName: string ]: Array<Type> }
  events: {
    onUnreadNotificationNumberChange: [Number /* newNumberOfNotifications */],
    onPermissionChange: [String /* Permission Name */, Boolean /* Permission Value */],
    onAddressChange: [
      {
        country: String,
        addressLine: String,
        extraAddressLine: Optional(String), // will have the `string | undefined` type
        codes: [String] // To represent string array
      }
    ],

    // The following parameter will not have a scheme to validate
    // as the ones defined above, but instead the received argument
    // will have the given type of `YourInterfaceHere`.
    onMessage: [CustomType<YourInterfaceHere>()],
  },

  // The methods that can be invoked/sent from the client-side (front-end) to
  // the server.
  actions: {
    sendMessage: {
      // The arguments to send/invoke the function on the client-side (front-end)
      input: [String /* Receiver ID */, String /* Message Content */],

      // The expected output from the server when it is `invoke`d, optional.
      output: Boolean
    },
    refreshStatus: {
      // No input
      input: [],

      // The output type.
      output: { id: Number, hasChanges: Boolean }
    },

    // The following is an example of an action with no output.
    voidAction: { input: [] }
  },

  // The following properties are optional
  //
  // The `effectModifier` and `callbackModifier` will be used to have
  // modifications/effects on the event functions, which might be useful
  // for React-like libraries.
  effectModifier: useEffect,
  callbackModifier: useCallback,

  // hubStartParameters: ...ObjectPropertiesForSignalRHub...
  // logger: ...LoggerForDebugging...
})

At this point, UserHub is defined and events can be listened and actions can be send or invoked.

---

Listening to events

Listening to events are done in two ways:

• addListener: Adds an event handler function for an event by name and returns an object containing unsubscribe function property that can be used to unsubscribe the event handler.
• useListener: Similar to addListener but aiming for React-like environments where a dependency array is passed along with the event listener to unsubscribe/resubscribe to events.

There are also two ways of adding event listeners:

• Using the events property of the defined hub objects.
• Using the addListener/useListener methods of defined hub objects directly.

The latter requires the event name (type-checked) and there is no other difference between them.

const unsubscriber = UserHub.events.onPermissionChange.addListener((permissionName, state) => {
  // Event handler body goes here.
})

// Stop listening to the event when it's not needed anymore.
unsubscriber.unsubscribe()

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

// Another way of event listening:
const unsubscriber = UserHub.addListener('onPermissionChange', (permissionName, state) => {
  // ...
})

---

Listening to events in React-like environments

For the React-like environments, it may be required to pass a dependency array to re-attach the event handler with the updated configurations. For such cases, .useListener method can be used. The signature of this method is the same with the .addListener with one additional, optional dependencyList parameter.

The handler functions are also passed to callbackModifier to have the effect of useCallback function.

The useCallback and useEffect effect functions can be passed to hub definitions.

function SomeComponent(props) {
  const [someDependency, setDependency] = useState()

  UserHub.events.onPermissionChange.useListener((permissionName, state) => {
    // Do something here with `someDependency`
  }, [ someDependency ])

  // It is the same if we call it in the following way:
  UserHub.useListener('onPermissionChange', (permissionName, state) => {
    // Do something here with `someDependency`
  }, [ someDependency ])

  return (
    <View/>
  )
}

---

Triggering actions

Calling a method on the server is done in two ways:

• Using send method. This will return a Promise that will resolve when the request is sent, not when the response is received.
• Using invoke method. This will return a Promise that resolves with the value received from the server.

// The following will not wait for the return value from the server
await UserHub.actions.sendMessage.send('receiverId', 'Hello from sender')

// The following will wait the return value from the server
const { id. hasChanges } = await UserHub.actions.refreshStatus.invoke()

---

Support

To support the project, you can send donations to following addresses:

- Bitcoin     : bc1qtut2ss8udkr68p6k6axd0na6nhvngm5dqlyhtn
- Bitcoin Cash: qzmmv43ztae0tfsjx8zf4wwnq3uk6k7zzgcfr9jruk
- Ether       : 0xf542BED91d0218D9c195286e660da2275EF8eC84
- Lightning   : coinos.io/incetarik