Function useHaystackPoint

useHaystackPoint<Value>(originaryPoint: Optional<Point<Value>>, pollRate?: number, writeOptions?: HaystackPointWriteOptions): [Optional<Value>, PointWriteFunc<Value> | undefined, Optional<Point<Value>>]
A hook that allows using a point from an haystack server as react state.

Important: This hooks requires a ClientContext to work.

See
https://github.com/j2inn/haystack-nclient

Example
Example of usage with a numeric point.
```
const point= useReadByFilter('point and temp and zone and sp').grid[0] // One-shot reading the first point that matches the filter
const [pointValue, setPointValue, updatedPoint] = useHaystackPoint<HNum>(point) // Using the point state
```
Returns
Returns the point value, a function to update it and the point dict.
Type Parameters
Type Parameters
- Value extends HVal<Value>
Parameters
- originaryPoint: Optional<Point<Value>>
  
  point dict used to retrieve its id and initial value.
- pollRate: number = 5
  
  poll rate for the value subscription. Expressed in seconds.
- Optional writeOptions: HaystackPointWriteOptions
  
  default options for the write callback.
Returns [Optional<Value>, PointWriteFunc<Value> | undefined, Optional<Point<Value>>]
- Defined in src/useHaystackPoint.ts:39