Source Node

A source node is a node that creates or wraps data into data frames. Examples on creating an active or passive source node can be found in the interactive notebook here.

Passive source node

A passive source node is a source that only returns a data frame when it is requested through a pull.

ts
import { SourceNode, DataFrame, DataObject, PullOptions, SourceNodeOptions } from '@openhps/core';
 
export class MyPassiveSource<Out extends DataFrame> extends SourceNode<Out> {
 
    constructor(options?: SourceNodeOptions) {
        super();
    }
 
    onPull(options?: PullOptions): Promise<Out> {
        return new Promise((resolve, reject) => {
            const object = new DataObject("mysensor");
            const frame = new DataFrame(object);
            resolve(frame as Out);
        });
    }
 
}

Active source node

An active source node is a source that automatically creates new data frames (e.g. a sensor that generates information at a fixed interval).

ts
import { SourceNode, DataFrame, DataObject, PullOptions, SourceNodeOptions } from '@openhps/core';
 
export class MyActiveSource<Out extends DataFrame> extends SourceNode<Out> {
    private _timer: NodeJS.Timeout = undefined;
 
    constructor(options?: SourceNodeOptions) {
        super();
 
        this.once('build', this._initSensor.bind(this));
        this.once('destroy', this._destroySensor.bind(this));
    }
 
    private _initSensor(): void {
        this._timer = setInterval(() => {
            const object = new DataObject("mysensor");
            const frame = new DataFrame(object);
            this.push(frame as Out);
        }, 1000);
    }
 
    private _destroySensor(): void {
        clearInterval(this._timer);
    }
 
    onPull(options?: PullOptions): Promise<Out> {
        return new Promise((resolve, reject) => {
            resolve(undefined);
        });
    }
 
}