observable.md

title
Observable

kendo.Observable

Provides support for firing events. Inherits from kendo.Class.

Methods

bind

Attaches a handler to an event.

Parameters

eventName String

The name of the event.

handler Function

A function to execute each time the event is triggered. That function should have a single parameter which will contain any event specific data.

Important: The context (this) of the handler function is set to the observable object itself.

Example - subscribing to an event

<script>
var obj = new kendo.Observable();
obj.bind("myevent", function(e) {
    console.log(e.sender === obj); // outputs "true"
    console.log(this === obj); // also outputs "true"
});
obj.trigger("myevent"); // causes the handler to be executed
</script>

one

Attaches a handler to an event. The handler is executed only once.

Parameters

eventName String

The name of the event.

handler Function

A function to execute each time the event is triggered. That function should have a single parameter which will contain any event specific data.

Important: The context (this) of the handler function is set to the observable object itself.

Example - subscribing to an event

<script>
var obj = new kendo.Observable();
var numberOfCalls = 0;
obj.one("myevent", function() {
    numberOfCalls ++; // increment the counter every time the handler is executed
});
obj.trigger("myevent"); // fire the event
obj.trigger("myevent"); // fire the event
console.log(numberOfCalls); // outputs "1"
</script>

trigger

Executes all handlers attached to the given event.

Parameters

eventName String

The name of the event to trigger.

eventData Object

Optional event data which will be passed as an argument to the event handlers.

Example - trigger an event

<script>
var obj = new kendo.Observable();
obj.bind("myevent", function(e) {
    console.log(e.data); // outputs "data"
});
obj.trigger("myevent", { data: "data" });
</script>

unbind

Remove a previously attached event handler.

Parameters

eventName String (optional)

The name of the event. If not specified all handlers of all events will be removed.

handler Function (optional)

The handler which should no longer be executed. If not specified all handlers listening to that event will be removed.

Example

<script>
var obj = new kendo.Observable();
var numberOfCalls = 0;
function handler(e) {
    numberOfCalls ++;
}
obj.bind("myevent", handler); // subscribe to the event
obj.trigger("myevent"); // fire the event
obj.unbind("myevent", handler); // unsubscribe from the event
obj.trigger("myevent"); // fire the event
console.log(numberOfCalls); // outputs "1"
</script>