yjs/examples/PeerJs-Json/README.md

PeerJs + JSON Example

Here, I will give a short overview on how to enable collaborative json with the PeerJs Connector and the JsonYatta Framework. First you have to include the following libraries in your html file:

<script src="http://open-app.googlecode.com/files/openapp.js"></script>
<script src="http://dbis.rwth-aachen.de/gadgets/iwc/lib/iwc.js"></script>
<script src="http://dbis.rwth-aachen.de/~jahns/role-widgets/widgetbundles/libraries/DUIClient.js"></script>
<script src="../../build/browser/Frameworks/JsonYatta.min.js"></script>
<script src="../../build/browser/Connectors/PeerJsConnector.min.js"></script>
<script src="./index.js"></script>

A working widget implementation is IwcJson.xml and the js-file is index.js

Create Connector

The PeerJs Framework requires an API key, or you need to set up your own PeerJs server. Get an API key from the Website. The first parameter of createPeerJsConnector is the options object in PeerJs.

var yatta, yattaHandler;
Y.createPeerJsConnector({key: 'h7nlefbgavh1tt9'}, function(Connector, user_id){

Yatta

yatta is the shared json object. If you change something on this object, it will be instantly shared with all the other collaborators.

  yatta = new Y.JsonYatta(user_id, Connector);

Add a integer-property like this

  yatta.val('x', 7);

Get the value of property x like this

  console.log(yatta.val('x') === 7); // true

A string property can be either mutable or immutable.

  yatta.val('mutable_string', "text", "mutable");
  yatta.val('immutable_string', "text", "immutable");

  console.log(yatta.val('immutable_string') === "text"); // true
  yatta.val('mutable_string').insertText(2,"XXX"); // position, string
  yatta.val('mutable_string').deleteText(0,1); // position, deletion length
  console.log(yatta.val('mutable_string').val() === "eXXXxt"); // true

You can omit the mutable - parameter. In that case the default will be used. Initially the default is 'mutable'. You can set it like this:

  yatta.setMutableDefault('mutable');
  // or
  yatta.setMutableDefault('immutable');

  yatta.val('new_string', "string");
  console.log(yatta.val('new_string') === "string"); // true

yatta is chainable:

  yatta.val('a', 4).val('b',5);
  console.log(yatta.val('a') === 4); // true
  console.log(yatta.val('b') === 5); // true

You can alse set objects.

  yatta.val('object', {a : {b : "b"}, c : { d : 5 }});
  console.log(yatta.val('object').val('c').val('d') === 5); // true

Lists are always immutable.

  yatta.val('list', [1,2,3]);
  console.log(yatta.val('list')[2] === 3); // true

Add listeners

Apply a 'addProperty' - listener to a JsonType.

  function addProperty(event_name, property_name){
    console.log("Property '" + property_name + "' was created!");
  };
  yatta.on('addProperty', addProperty);
  yatta.val('new', {z: 7}); // Property 'new' was created!

Apply a 'change' - listener to a JsonType.

  function change(event_name, property_name){
    console.log("Property '" + property_name + "' was replaced or changed!");
    console.log("New value: \"" + this.val(property_name).val() + "\""); // 'this' is the new/created value
  };
  yatta.on('change', change);
  yatta.val('mutable_string', "text", 'mutable'); // Property 'mutable_string' was replaced or changed!

Does not fire for nested properties.

  yatta.val('q').val('z', 8); // No output!

Apply 'insert' and 'delete' - listeners to Words.

  function insert_delete(event_name, op){
    if (event_name === "insert"){
      console.log("Inserted '" + op.content + "' at position " + op.getPosition());
    } else if (event_name === "delete"){
      console.log("Deleted character at position " + op.getPosition());
    }
  };
  yatta.val('mutable_string').on(['insert', 'delete'], insert_delete);
  yatta.val('mutable_string').insertText(0, 'a'); // Inserted 'a' at position 0
  yatta.val('mutable_string').deleteText(0, 1); // Deleted character at position 0

  yatta.deleteListener('addProperty', addProperty);
  yatta.deleteListener('change', change);
  yatta.deleteListener('insert_delete', insert_delete);

Experimental method

But there is a much more convenient way!

  console.log(yatta.value.list[2] === 3) // true
  yatta.value.list = [3,4,5]
  console.log(yatta.val('list')[2] === 5) // true
  yatta.value.object = {c : 4}
  console.log(yatta.value.object.c === 4) // true

The downside is that you are only allowed to overwrite existing properties.

  yatta.value.newProperty = "Awesome"
  console.log(yatta.value.newProperty !== "Awesome") // true, yatta.value.newProperty is undefined.

So, how do we create new properties?

  yatta.value = {newProperty : "Awesome"}
  console.log(yatta.value.newProperty === "Awesome") // true, it's awesome ;)

This is stupid! I don't want to overwrite all my existing properties! Very well.. The solution is that we merge yatta.value with the new assignment. For example: assuming we want to overwrite yatta.value with some object o. Then these two rules apply:

• The result has all properties of o
• The result has all properties of yatta.value if they don't occur under the same property-name in o

  yatta.value = {newProperty : {Awesome : true }}
  console.log(yatta.value.list[2] === 5) // true, old value list still exists.
  console.log(yatta.value.newProperty.Awesome === true) // true, newProperty is overwritten.

Consider this case.

  yatta.value = {newProperty : { x : 4} }
  console.log(yatta.value.newProperty.Awesome == null) // true, newProperty was replaced, therefore it is now undefined

Did you notice that you always set immutable objects if you set properties like this? Even if the default is 'mutable'. If you want to work with mutable objects you have to work with .val().

One last thing. You are only allowed to set properties like this yatta.value = o. Yatta can't observe if you overwrite object references yatta = "Awesome".

  w = yatta.value.newProperty
  w = "Awesome"
  console.log(yatta.value.newProperty !== "Awesome") // true, still not awesome..

Please also read JsonWrapper

});