Building Custom Apps

The NC.js package provides a baseline that a web programmer can extend for your own local needs. Typically, an app will have some new capability provided by the server and matching UI elements in the client to present or control it.

The existing NC.js source code contains a sample application that you can use as a starting point for your own code. This sample searches through a digital thread model for alternative workplans, groups them by name, and presents them as buttons for switching between the options. We will walk through the server and client code to do this in the sections below.

custom app
Custom Configuration Buttons, Mixed Config

The "Moldy" model has Profile and Pocketing alternatives named Boeing, Iscar, and Sandvik. The model starts with a mix - the Sandvik plan is selected for profiling and the Iscar plan for pocketing. These partial configs are shown in yellow. Clicking on one of them will select that for both operations and hilight the button in blue.

custom app
Custom Configuration Buttons, All Sandvik

To make this happen, we implement a new custom REST endpoint, at /v3/custom/config that finds the current configuration, or sets it if given an argument. The endpoint returns a JSON object with an array of all configs, and the name of the selected one. We also inplement an event, called "custom:config", that gets sent to all connected clients when the config is changed. This keeps all of the clients in sync if more than one is looking at the server.

GET http://localhost:8080/v3/custom/config
  or "partial": [ list of configs ] if a mix

Change the config to Boeing
GET http://localhost:8080/v3/custom/config/Boeing

Running the Custom Application

The code for the custom configuration app is included with the NC.js source but is /* block commented */ out. To try this sample app, search for and uncomment all code marked with the string "CUSTOM-APP" in the following files, then rebuild with npm run make.

Custom Server Endpoints

The existing server endpoints cover a variety of information and behavior. When your App needs something beyond these for its new capability, add your own REST endpoints under the /v3/custom prefix. In our sample, we add the /v3/custom/config endpoint.

The source for the new endpoint in NC.js/src/server/api/v3/custom.js. The server endpoints are implemented as javascript functions that use the Finder, Tolerance, APT, and Adaptive parts of the STEP-NC API to get detailed information from the digital thread model. You can prototype the interesting parts of your endpoints as plain node programs. When you move the code into the server, you will get the parameters as part of the request URL and return JSON object to the client along with a status code.

The module exports at the end of the file connects the REST endpoints with javascript functions using Express.js. Here, the _getConfig() function is always called for an HTTP GET on the the base config endpoint and the one that is followed by a name parameter. The Express.js docs have more about parameters and endpoint routing.

The NC.js/src/server/api_server.js file will call this exported function for custom.js and the other server source files. If you put your endpoints in a new source file, be sure to add it to the chained calls in APIServer.prototype._setRoutes.

module.exports = function(globalApp, cb) {
  app = globalApp;
  app.router.get('/v3/custom/config',       _getConfig);
  app.router.get('/v3/custom/config/:name', _getConfig);
  if (cb) { cb(); }

The _getConfig() function computes the existing config if it is not yet known, checks whether it has been called with the "name" parameter, and either returns the config or changes to the requested one and returns the updated config. When it changes the config, it also sends an event named "custom:config" via the websockets that all clients listen on. The event includes the new config as an argument.

var cfg = {};

function _getConfig(req,res) {
  // find existing config 
  if (cfg.configs === undefined) {
    cfg = _findConfig();
  if (( !== undefined) &&
      (cfg.configs.includes( {
    // change config, send new, issue event
    cfg = _setConfig(;
    app.ioServer.emit('custom:config', cfg);
  } else {
    // send existing config

Finding the config is just a simple traversal using STEP-NC API code. This was prototyped as simple node programs and then dropped into the server. The Adaptive object walks the process, looking at all executables, even those that are disabled. It stops at each exec that is an element of a Selective (the STEP-NC process element that holds alternatives), then adds the ID and enabled/disabled state to a dictionary, grouped by name.

function _findConfig() {
  let ctl = new StepNC.Adaptive();

  // Look at the elements of all selectives.  Group by name

  let execs = {};
  while (ctl.Next()) {
    let id = ctl.GetActiveExec();
    let nm = file.find.GetExecutableName(id);

    if (execs[nm] === undefined) {
      execs[nm] = [];
    execs[nm].push({'id': id, 'active': file.find.IsEnabled(id) });

At the end, the configs are the unique names from the dictionary. We also compute a list of configs that have at least one executable enabled and the subset that have all of their executables enabled. If we only have one for both, that is the selected config, otherwise we return the list of partials.

  let ret = {
    "configs": Object.keys(execs).sort()
  // look for configs that have some enabled WSs enabled and ones that
  // have everything enabled.  Selected if both lists have one entry.
  let partial = ret.configs.filter(
    nm => execs[nm].find(elem =>

  let selected = partial.filter(
    nm => execs[nm].every(elem =>

  if ((partial.length === 1) && (selected.length === 1)) {
    ret.selected = selected[0];
  } else if (partial.length > 0) {
    ret.partial = partial;
  return ret;

The _setConfig() also loops over all selectives with using the Adaptive class. In this case it just adjusts the enabled flag of each element depending on whether its name matches a given value.

Custom Client UI

The client UI is implemented as a collection of React.js components. These can be found under the NC.js/src/client/views directory. The responsive view is the root component and acts as the clearinghouse for data on the client. It maintains state information and dispatches the notification events recieved via the websocket that the client sets up with the server. We also modify the header view to display the configuration as a series of buttons. These two files are:

When writing client javascript, you automatically have access to all of the plugins listed below, at the given symbol. The most current list can be found in the webpack.config.js file listed under the "plugins" tag.

Responsive View

In the constructor(), we add a custom entry to the state object for our application. React will track which UI subcomponents use each state variable, and when a state variable changes, it will force that component to re-render to show the new information.

this.state = {
  [ ... other variables ... ] 
  // CUSTOM APP STATE - for sample application that changes the
  // workplan between several predefined configs.
  custom_config: null

We add a getCustomConfig() function to parse the JSON sent back from our custom REST endpoint and update the state variable if needed. There is also an entry in the addBindings() function to give our config function access to the state variable.

In addListeners(), we watch for an event and update the client data as needed. This is the notification from the server to all connected clients when the workplan has changed. This code updates the client state for the workplan, which updates any UI elements that use it.'custom:config', (cfg)=>{
  let old_cfg = this.state.custom_config;

  if ((old_cfg === null) ||
      (old_cfg.selected !== cfg.selected)) {
    this.setState({'custom_config' : cfg});

  // request new workplan and tool data if config changed
  if ((old_cfg !== null) &&
      (old_cfg.selected !== cfg.selected)) {
	// get the cache of tools, need workplan first
	return request.get('/v3/nc/tools/');

In componentWillMount() which is called when the client first loads, we request the config from the server using our custom REST endpoint, and set our state variable using the getCustomConfig() function.

// CUSTOM-APP - Get available configs at startup

Finally, in the render() function, we pass the config state variable to the HeaderView component, which will show it on the screen and possibly call the REST endpoints to change configs. This is discussed in the next section.

  [ ... many other variable assignments ... ]

  // CUSTOM-APP - Pass config to header object
  cfg = {this.state.custom_config}

Header View

In the header/index.jsx file, we define a new class to display the configuration menu. In the render() function for this class, we generate a DIV with a button for each name in the configuration array.

The color of the button is deternined by the configstyle() function, which returns a different CSS style depending on whether it is the selected, partially selected, or unselected configuration.

Finally, the click event is handled by the cfgClick() function which calls the custom REST endpoint with the new config name.

class ConfigMenu extends React.Component {
  constructor(props) {
    this.cfgClick = this.cfgClick.bind(this);

  render() {
    let cfg = this.props.cfg;
    if (cfg === undefined) { cfg = { configs: [] }; }
    return (
      { => (
	  <div className={configstyle(cfg,nm)}
	     onClick={() => {this.cfgClick(nm);}}>{nm}</div>

Finally, in the render() function of the HeaderView class, we use the ConfigMenu element and pass in the parameters that it needs to display.

// CUSTOM-APP - Add config menu to header
<ConfigMenu cfg={this.props.cfg} actionManager={this.props.actionManager}/>