Streams

Definition

But first, an experiment!
Flowing through instead of stopping every step

List structure, but not all values at once (Delayed List)
Operate without having to know or care when the data flow ends (or if it ever ends)
Operate without having to know or care how much data is in the stream in total

Have you used streams?

youtube.com

Have you used streams?

Pipes

When? / Why?

Can't / Don't want to hold everything in memory
Use less bandwidth
Able to work with (potentially) infinite data
Separation of concerns (e.g. in Unix)

Push Streams

Producer: "Have the data."
Pushes data out
Someone handles it when it arrives
"Callback"
Non-blocking
Possible overload: "back pressure"
- Block at the source
- Sample (most recent)
- First only
- Debounce
- Buffer
- ...

Pull Streams

Consumer: "Can I get some data?"
Consumer gets data themselves
"Iterator"
Blocking: "Timeout"

Let's program!

Reactive

Reactive?

In computing, reactive programming is a programming paradigm oriented around data flows and the propagation of change. This means that it should be possible to express static or dynamic data flows with ease in the programming languages used, and that the underlying execution model will automatically propagate change through the data flow.

Wikipedia

Passive Reactive

Foo updates Bar when something in Foo changes

Bar listenes to Events happening in Foo and updates itself

Reacts to an Event

$('#cats-btn').click(function () {  
  getDataFromServer('cats');
});

function formatCats(cat) {  
  return { name: 'Hello ' + cat.name }
}

function renderUI(data) {  
  UI.render(data);
}

function getDataFromServer(type) {  
  $.ajax(URL + type).done(function (cats) {
    renderUI(cats.map(formatCats));
  });
}

_('click', $('#cats-btn'))
  .pipe(getDataFromServer)
  .map(formatCats)
  .pipe(UI.render);

No intermediate variables
Clear data flow
Doesn't work with individual events, but instead with event streams
Raises the abstraction level - focus on implementation of events rather than combined details

Passive Reactive

Reactive Pattern

By queicherius