ucsc-xena-client/dist/multi.js

UCSC Xena Client. Functional genomics visualizations.

'use strict';

var _ = require('./underscore_ext');

// Ad hoc polymorphism, a bit like clojure's multimethods: a way to dispatch
// based on any criteria (instead of just on 'this').
//
// e.g. dispatching on the 2nd parameter:
//
// scribble = multi(function(name, val) { return val; })
// scribble.add('crayon', function(name, val) { crayon('name'); })
//
// Set fn.dflt if a default is required.
// The dispatch function may be modified by calling fn.dispatchfn.
// If arity is specified, the function wlil be curried.
function multi(dispatchfn, arity) {
	var methods = {},
	    getmethod = function getmethod() {
		var dispatch = dispatchfn.apply(this, arguments),
		    method = methods[dispatch] || fn.dflt; //eslint-disable-line no-use-before-define

		if (typeof method !== 'function') {
			throw new Error('No method for ' + dispatch);
		}
		return method;
	},
	    fn = function fn() {
		var method = getmethod.apply(this, arguments);

		return method.apply(this, arguments);
	};

	if (arguments.length > 1) {
		fn = _.curryN(arity, fn);
	}
	fn.dispatchfn = function (fn) {
		return dispatchfn = fn;
	};
	fn.add = function (dispatch, fn) {
		methods[dispatch] = fn;
	};

	return fn;
}

module.exports = multi;