Hooks
The
useTelemetry hook makes it very easy to just listen to telemetry on a single device.const value = useTelemetry(deviceId, telemetryKey, { onData, onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device ID of the device from which to receive telemetry data | string | |
telemetryKey | The key of the telemetry item | string | |
options | Configuration Options | HookOptions |
HookOptions
key | Description | value type | required |
|---|---|---|---|
onData | Callback, executed when new telemetry of telemetryKey is received on the device | (data: unknown) => void | |
onGrantError | Callback, executed when the grantRequestFunction fails to grant the direct method request | GrantErrorCallback |
This hook returns a single value. Every time the device sends new telemetry with key
telemetryKey this hook will update this value.This hook relies on the assumption that your Device-to-Cloud messages are JSON documents where the key is the telemetry key and the value is the current telemetry value. We plan to support more complex payloads in the future (selecting using JSON Path, Avro, etc). If you have other message payloads, you can use the useD2CMessage hook.
A component subscribing to the
temperature telemetry.const temperature = useTelemetry('simulated-device', 'temperature');
return (
<div>
<h3>Current Temperature of simulated-device</h3>
<div>{temperature}</div>
</div>
);
The D2C messages are expected to look like this:
{
"temperature": 42.1,
...
}
The
useMultiTelemetry hook is a more sophisticated variant of useTelemetry. It is designed to cover use-cases where a several streams of telemetry of multiple devices need to be subscribed to.const { telemetry, addTelemetry, removeTelemetry } = useMultiTelemetry();
const {
telemetry,
toggleTelemetry,
isSubscribed,
currentSubscribers,
addTelemetry,
removeTelemetry,
} = useMultiTelemetry({
initialSubscribers: { [deviceId]: ['temperature', 'pressure'] },
onData: (deviceId, key, value) => console.log(deviceId, key, value),
onGrantError: error => console.log(error)
});
// Example of a component utilising the "toggleTelemetry" mechanism to
// toggle subscriptions to two datapoints "temperature" and "pressure"
import { FC } from 'react';
import { TelemetryValue, useMultiTelemetry } from 'ux4iot-react';
const DeviceValue: FC<TelemetryValue> = ({ value, timestamp }) => {
return (
<div>
{value} - received at {timestamp}
</div>
);
};
type Props = {
deviceId: string;
datapoints: string[];
};
const TestMultiSubscriber: FC<Props> = ({ deviceId, datapoints }) => {
const { telemetry, toggleTelemetry, isSubscribed } = useMultiTelemetry({
initialSubscribers: { [deviceId]: datapoints },
});
return (
<div>
{datapoints.map(dp => (
<div key={dp}>
<label>{dp}</label>
<input
type="checkbox"
checked={isSubscribed(deviceId, dp)}
onChange={() => toggleTelemetry(deviceId, dp)}
/>
{telemetry[deviceId] && <DeviceValue {...telemetry[deviceId][dp]} />}
</div>
))}
</div>
);
};
const App = () => {
return (
<Ux4iotContextProvider options={...}>
<TestMultiSubscriber
deviceId="simulated-device"
datapoints={['temperature', 'pressure']}
/>
</Ux4iotContextProvider>
);
};
Argument | Description | Type | Required? |
|---|---|---|---|
options | Configuration Options | HookOptions |
Argument | Description | Type | Required? |
|---|---|---|---|
initialSubscribers | Object of key-value pairs, with keys: the device IDs of your IoTHub devices, and value: a list of strings, defining the telemetryKeys to subscribe to | Record<string, string[]> | |
onData | Callback, executed when a new value for a telemetryKey is sent by a device with ID deviceId | (deviceId: string, telemetryKey: string, value: unknown) => void | |
onGrantError | Callback, executed when the grantRequestFunction fails to grant the subscription request. | GrantErrorCallback |
Do not try to perform subscription updates over the
initialSubscribers object. This object is meant solely as an option for use cases where you always have an initial set of subscribers. Updates to initialSubscribers will not trigger updates in the hook.This hook returns an object containing other objects and functions to interact with telemetry subscriptions.
Key | Value | Type |
|---|---|---|
telemetry | Object holding the current values of all your telemetry subscriptions | Record<string, Record<string, unknown> |
toggleTelemetry | Toggles a telemetry subscription for a deviceId and telemetryKey | (deviceId: string, telemetryKey: string) => void |
addTelemetry | Adds a telemetry subscription for a deviceId and multiple telemetryKeys | (deviceId: string, telemetryKeys: string[]) => void |
removeTelemetry | Removes a telemetry subscription for a deviceId and multiple telemetryKeys | (deviceId: string, telemetryKeys: string[]) => void |
isSubscribed | Checks whether a telemetry subscription for a deviceId and telemetryKey exists | (deviceId: string, telemetryKey: string) => boolean |
currentSubscribers | Object containing all current subscribers with key being the deviceId and value being the telemetryKey names. | Record<string, string[]> |
The
useDirectMethod hook returns a function that, when invoked, calls a direct method on the target device. It returns a Promise that resolves to the direct method result that the device returns (or an error when the direct method could not be executed, e.g. if the device is offline).const reboot = useDirectMethod(deviceId, methodName, { onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device ID of the device to execute the direct method on | string | |
methodName | The name of the method to execute on the device | string | |
options | Configuration Options | HookOptions |
Hook Options
Argument | Description | Type | Required? |
|---|---|---|---|
onGrantError | Callback, executed when the grantRequestFunction fails to grant the direct method request | GrantErrorCallback |
This hook returns a function:
(params: Record<string, unknown>) => Promise<IotHubResponse | void>IoTHubResponse
{
status: number;
payload: unknown:
}
You pass the method payload to this function and it outputs the result of the direct method invocation on the device.
Do not confuse the
onGrantError handler of useDirectMethod with the catch block of the direct method itself. onGrantError will only be executed when this hook is rendered by react and the security backend fails to grant the direct method. The error that reboot may throw is an HTTP error that could occur when the function is executed.const reboot = useDirectMethod(deviceId, 'reboot', {
onGrantError: error => console.log(error)
});
const result = useState<unknown>();
const error = useState<string>();
const handleClick = () => {
const payload = { delay: 2000 };
reboot(payload)
.then(result => setState(result))
.catch(error => setError(error));
}
return <button onClick={() => handleClick()}>Reboot Device</button>
The
useDeviceTwin hook subscribes to device twin updates.const deviceTwin = useDeviceTwin(deviceId, { onData, onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device id of the device you want to subscribe to. | string | |
options | Configuration Options | HookOptions |
Hook Options
Argument | Description | Type | Required? |
|---|---|---|---|
onData | Callback, executed when a new twin updated is received. | (twin: Twin) => void | |
onGrantError | Callback, executed when the grantRequestFunction fails to grant the subscription request. | GrantErrorCallback |
This hook returns a value:
TwinThis hook returns the device twin whenever twin updates are made on the IoTHub device. This hook uses the
Twin typescript type provided from the azure-iothub library.Here is an example of a returned device twin:
{
"version": 2,
"tags": {
"$etag": "123",
"deploymentLocation": {
"building": "43",
"floor": "1"
}
},
"properties": {
"desired": {
"telemetryConfig": {
"sendFrequency": "5m"
},
"$version": 1
},
"reported": {
"telemetryConfig": {
"sendFrequency": "5m",
"status": "success"
},
"batteryLevel": 55,
"$version": 4
}
}
}
The
useConnectionState hook subscribes to the connection state of a device. This state can change, i.e as soon as a device connects or disconnects.const connectionState = useConnectionState(deviceId, { onData, onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device id of the device you want to subscribe to. | string | |
options | Configuration Options | HookOptions |
Hook Options
Argument | Description | Type | Required? |
|---|---|---|---|
onData | Callback, executed when a new connectionState update is received. | (connectionState: boolean) => void | |
onGrantError | Callback, executed when the grantRequestFunction fails to grant the subscription request. | GrantErrorCallback |
This hook returns a value:
booleanThis value changed as soon as a device connects or disconnects.
The
usePatchDesiredProperties hook is used to perform desired property updates on devices.const patchDesiredProperties = usePatchDesiredProperties(deviceId, { onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device id of the device onto which to patch the desired properties | string | |
options | Configuration Options | HookOptions |
Hook Options
Argument | Description | Type | Required? |
|---|---|---|---|
onGrantError | Callback, executed when the grantRequestFunction fails to grant the patch desired properties request. | GrantErrorCallback |
This hook returns a function:
(desiredProperties: Record<string, unknown>) => Promise<IoTHubResponse | void>IoTHubResponse
{
status: number;
payload: unknown:
}
The hook takes in an object of desired properties to send to the device with the specified device ID.
When you call the function returned by this hook you will inevitably perform a device twin update. This means you will receive an update of the output of
useDeviceTwinconst patchDesiredProperties = usePatchDesiredProperties('simulated-device');
const handleClick = () => {
patchDesiredProperties({
temperature: 21
});
}
return <button onClick={() => handleClick()}>Update desired properties</button>
const lastMessage = useD2CMessages<T>(deviceId, { onData, onGrantError });
Argument | Description | Type | Required? |
|---|---|---|---|
deviceId | The device ID of the device you want to subscribe to. | string | |
options | Configuration Options | HookOptions |
Hook Options
Argument | Description | Type | Required? |
|---|---|---|---|
onData | Callback, executed when the device sends a new message. | (data: Record<string, unknown>) => void | |
onGrantError | Callback, executed when the grantRequestFunction fails to grant the subscription request. | GrantErrorCallback |
This hook returns the generic type you specified:
TMessages received over this hook have the type
unknown first and are then casted to your type T. Omitting this generic type will leave the type unknown.We assume that every message a device sends will be an object. The return value of this hook will always be the last message sent by the device.
The hooks provided by ux4iot-react are using a specific authorization mechanism. They are designed to provide the easiest API to cover your use-case and hide the most complexity possible. There are two callbacks that are available on (almost) every hook.
A convenient callback to have a custom callback whenever data is received. You will receive updates of subscription hooks mostly over the return value. However, if you want to use custom logic whenever an update is received you would need to use custom hooks to listen for these changes like this:
const value = useX(deviceId, ...);
useEffect(() => {
console.log('Update to value detected')
}, [value]);
Therefore
onData as function in subscription hooks, removes the burden of you needing to decide when to notice value changes.This callback exists on every hook. The purpose of this callback is to inform you about errors that the custom
grantRequestFunction returns. The grantRequestFunction is something that you need to implement yourself when you want to use ux4iot in production. The purpose of this function is to determine whether you as a user of the react application have the permission to subscribe to telemetry / device twin / connection state or perform a direct method / desired property patch.