can-connect/data/worker/worker

module

Connects a connection to another connection in a worker thread.

`dataWorker( baseConnection )`

If a Worker is provided, overwrites the "data interface methods" to package the arguments and send them as part of a postMessage to the Worker.

If a Worker is not provided, it is assumed "data-worker" is being added within a worker thread. It listens to messages sent to the Worker, calls the specified "data interface method" and sends a message back with the result.

Any data methods called on the window connection will wait until the worker connection has established a handshake.

Use

The best way to use data/worker is to create a connection module that works when loaded in either the window or in a Worker. This pattern tends to work even if workers are not supported.

The following creates a connection that does the work of can-connect/cache-requests/cache-requests, can-connect/data/url/url, and can-connect/data/memory-cache/memory-cache in a worker thread.

The todo_connection module can be found here and looks like the following:

var connect = require("can-connect");
var fixture = require("can-fixture");

// If we are in the main thread, see if we can load this same
// connection in a worker thread.
var worker;
if(typeof document !== "undefined") {
    worker = new Worker( System.stealURL+"?main=can-connect/data/worker/demo/todo_connection" );
}


// create cache connection
var cache = connect([
    require("can-connect/data/memory-cache/")
],{
    name: "todos"
});

// Create the main connection with everything you need.  If there is a worker,
// all data interface methods will be sent to the worker.
var todosConnection = connect([
    require("can-connect/data/url/url"),
    require("can-connect/cache-requests/cache-requests"),
    require("can-connect/data/worker/worker"),
    require("can-connect/constructor/constructor"),
    require("can-connect/constructor/store/store")
],{
    url: "/todos",
    cacheConnection: cache,
    worker: worker,
    name: "todos"
});


fixture.delay = 1000;
fixture({
    "GET /todos": function(request){
        return {data: [
            {id: 1, name: "wash dishes"},
            {id: 2, name: "mow lawn"},
            {id: 3, name: "do laundry"}
        ]};
    }
});

module.exports = todosConnection;

The things to notice:

A Worker should be passed as the worker option that loads a connection with the same name as the connection in the window. In thise case, the same connection module is loaded so everything works.
A single Worker could load multiple connection modules and perform other behaviors.

Split Connection Logic

THe previous example used a single module that was loaded by both the window and the worker. This doesn't have to be the case. Two different modules could be used. For example, todo-window.js and todo-worker.js. Each might look like:

// todo-window.js
var workerURL = System.stealURL+"?main=app/models/todo-worker";

var todoConnection = connect([
    require("can-connect/data/worker/worker"),
    require("can-connect/constructor/constructor"),
    require("can-connect/constructor/store/store"),
  {
    worker: new Worker( workerURL ),
    name: "todos"
  });

// todo-worker.js
var cache = connect([
    require("can-connect/data/memory-cache/memory-cache")
],{
    name: "todos-cache"
});

var todoConnection = connect([
    require("can-connect/data/url/url"),
    require("can-connect/cache-requests/cache-requests"),
    require("can-connect/data/worker/worker")
],{
    url: "/todos",
    cacheConnection: cache,
    name: "todos"
  });

However, the problem with the two-module approach is that it will not work if Workers are not supported by your browser.