Plugin Data Fetcher Development

Plugin data fetchers are classes that can be used by HiGlass to fetch track data, but have an external code base. We strongly recommend to develop new types of data fetchers as plugin data fetchers and only add very generic data fetchers so the HiGlass core library.

Basic skeleton

A plugin data fetcher consists of a wrapper function which defines and returns an instance of a data fetcher class. The wrapper function loads HiGlass specific libraries which can be used in the definition of the plugin data fetcher class. In the follow you can see a bare minimum example of this structure.

import { registerDataFetcher } from 'higlass-register';

const MyPluginDataFetcher = function MyPluginDataFetcher(HGC, ...args) {
  if (!new.target) {
    throw new Error(
      'Uncaught TypeError: Class constructor cannot be invoked without "new"'
    );
  }

  // You can extend the base DataFetcher class with your plugin.
  const { DataFetcher } = HGC.factories;

  // Other libraries, utils, etc. that are provided by HiGlass (HGC)
  const { ... } = HGC.libraries;
  const { ... } = HGC.utils;
  const { ... } = HGC.services;
  const { ... } = HGC.utils;
  const { ... } = HGC.configs;

  // The version of HiGlass. Can be used to check for compatibility.
  const hgVersion = HGC.VERSION;

  class MyDataFetcherClass extends HGC.factories.DataFetcher {
    constructor(dataConfig, pubSub) {
        super(dataConfig, pubSub);
        this.hgc = HGC;
    }
  }
  return new MyDataFetcherClass(...args);
}

MyPluginDataFetcher.config = {
  type: 'my-data-fetcher',
};

// It's important that you register your plugin data fetcher
// with HiGlass otherwise HiGlass will not know about it
registerDataFetcher({
  name: 'MyPluginDataFetcher',
  dataFetcher: MyPluginDataFetcher,
  config: MyPluginDataFetcher.config
});

export default MyPluginDataFetcher;

The best way to get start implementing a plugin data fetchers is to take a look at existing plugin data fetchers and their code. You can find a list of all officially supported plugin tracks and data fetchers at higlass.io/plugins

Available libraries and utils

Plugin data fetchers have access to many core libraries and internal utilities.

Please visit the “available to plugins” page for an overview of all available imports that plugin tracks and data fetchers may access.