Pops up a tooltip (a help message) when you hover over a node. Also provides static show() and hide() methods that can be used without instantiating a dijit/Tooltip.
| Parameter | Type | Description |
|---|---|---|
| params | Object | null | Hash of initialization parameters for widget, including scalar values (like title, duration etc.) and functions, typically callbacks like onClick. The hash can contain any of the widget's properties, excluding read-only properties. |
| srcNodeRef | DOMNode | String |
Optional If a srcNodeRef (DOM node) is specified:
|
See the dijit/Tooltip reference documentation for more information.
Path to a blank 1x1 image.
Used by <img> nodes in templates that really get their image via CSS background-image.
Deprecated. Instead of attributeMap, widget should have a _setXXXAttr attribute for each XXX attribute to be mapped to the DOM.
attributeMap sets up a "binding" between attributes (aka properties) of the widget and the widget's DOM. Changes to widget attributes listed in attributeMap will be reflected into the DOM.
For example, calling set('title', 'hello') on a TitlePane will automatically cause the TitlePane's DOM to update with the new title.
attributeMap is a hash where the key is an attribute of the widget, and the value reflects a binding to a:
DOM node attribute
focus: {node: "focusNode", type: "attribute"} Maps this.focus to this.focusNode.focus
DOM node innerHTML
title: { node: "titleNode", type: "innerHTML" } Maps this.title to this.titleNode.innerHTML
DOM node innerText
title: { node: "titleNode", type: "innerText" } Maps this.title to this.titleNode.innerText
DOM node CSS class
myClass: { node: "domNode", type: "class" } Maps this.myClass to this.domNode.className
If the value is an array, then each element in the array matches one of the formats of the above list.
There are also some shorthands for backwards compatibility:
"focusNode" ---> { node: "focusNode", type: "attribute" }
Root CSS class of the widget (ex: dijitTextBox), used to construct CSS classes to indicate widget state.
Id of domNode(s) to attach the tooltip to. When user hovers over specified dom node(s), the tooltip will appear.
Designates where children of the source DOM node will be placed. "Children" in this case refers to both DOM nodes and widgets. For example, for myWidget:
<div data-dojo-type=myWidget>
<b> here's a plain DOM node
<span data-dojo-type=subWidget>and a widget</span>
<i> and another plain DOM node </i>
</div>
containerNode would point to:
<b> here's a plain DOM node <span data-dojo-type=subWidget>and a widget</span> <i> and another plain DOM node </i>
In templated widgets, "containerNode" is set via a data-dojo-attach-point assignment.
containerNode must be defined for any widget that accepts innerHTML (like ContentPane or BorderContainer or even Button), and conversely is null for widgets that don't, like TextBox.
This variable controls the position of tooltips, if the position is not specified to the Tooltip widget or *TextBox widget itself. It's an array of strings with the values possible for dijit/place.around(). The recommended values are:
The list is positions is tried, in order, until a position is found where the tooltip fits within the viewport.
Be careful setting this parameter. A value of "above-centered" may work fine until the user scrolls the screen so that there's no room above the target node. Nodes with drop downs, like DropDownButton or FilteringSelect, are especially problematic, in that you need to be sure that the drop down and tooltip don't overlap, even when the viewport is scrolled so that there is only room below (or above) the target node, but not both.
Bi-directional support, as defined by the HTML DIR attribute. Either left-to-right "ltr" or right-to-left "rtl". If undefined, widgets renders in page's default direction.
This is our visible representation of the widget! Other DOM Nodes may by assigned to other properties, usually through the template system's data-dojo-attach-point syntax, but the domNode property is the canonical "top level" node in widget UI.
This widget or a widget it contains has focus, or is "active" because it was recently clicked.
Number of milliseconds to wait after unhovering the object, before the tooltip is hidden. Note that blurring an object hides the tooltip immediately.
A unique, opaque ID string that can be assigned by users or by the system. If the developer passes an ID which is known not to be unique, the specified ID is ignored and the system-generated ID is used instead.
HTML to display in the tooltip. Specified as innerHTML when creating the widget from markup.
The document this widget belongs to. If not specified to constructor, will default to srcNodeRef.ownerDocument, or if no sourceRef specified, then to the document global
See description of dijit/Tooltip.defaultPosition for details on position parameter.
CSS expression to apply this Tooltip to descendants of connectIds, rather than to the nodes specified by connectIds themselves. Useful for applying a Tooltip to a range of rows in a table, tree, etc. Use in conjunction with getContent() parameter. Ex: connectId: myTable, selector: "tr", getContent: function(node){ return ...; }
The application must require() an appropriate level of dojo/query to handle the selector.
Number of milliseconds to wait after hovering over/focusing on the object, before the tooltip is displayed.
One of:
HTML title attribute.
For form widgets this specifies a tooltip to display when hovering over the widget (just like the native HTML title attribute).
For TitlePane or for when this widget is a child of a TabContainer, AccordionContainer, etc., it's used to specify the tab label, accordion pane title, etc. In this case it's interpreted as HTML.
When this widget's title attribute is used to for a tab label, accordion pane title, etc., this specifies the tooltip to appear when the mouse is hovered over that text.
Step during widget creation to copy widget attributes to the DOM according to attributeMap and _setXXXAttr objects, and also to call custom _setXXXAttr() methods.
Skips over blank/false attribute values, unless they were explicitly specified as parameters to the widget, since those are the default anyway, and setting tabIndex="" is different than not setting tabIndex at all.
For backwards-compatibility reasons attributeMap overrides _setXXXAttr when _setXXXAttr is a hash/string/array, but _setXXXAttr as a functions override attributeMap.
Reflect a widget attribute (title, tabIndex, duration etc.) to the widget DOM, as specified by commands parameter. If commands isn't specified then it's looked up from attributeMap. Note some attributes like "type" cannot be processed this way as they are not mutable.
| Parameter | Type | Description |
|---|---|---|
| attr | String | Name of member variable (ex: "focusNode" maps to this.focusNode) pointing to DOMNode inside the widget, or alternately pointing to a subwidget |
| value | String | |
| commands | Object |
Optional
|
Internal helper for directly changing an attribute value.
Directly change the value of an attribute on an object, bypassing any accessor setter. Also handles the calling of watch and emitting events. It is designed to be used by descendant class when there are two values of attributes that are linked, but calling .set() is not appropriate.
| Parameter | Type | Description |
|---|---|---|
| name | String | The property to set. |
| value | Mixed | The value to set in the property. |
Internal helper for directly changing an attribute value.
Helper function to get value for specified property stored by this._set(), i.e. for properties with custom setters. Used mainly by custom getters.
For example, CheckBox._getValueAttr() calls this._get("value").
| Parameter | Type | Description |
|---|---|---|
| name | String |
Helper function for get() and set(). Caches attribute name values so we don't do the string ops every time.
| Parameter | Type | Description |
|---|---|---|
| name | undefined |
Collect metadata about this widget (only once per class, not once per instance):
- list of attributes with custom setters, storing in this.constructor._setterAttrs - generate this.constructor._onMap, mapping names like "mousedown" to functions like onMouseDown
Helper function to set new value for specified property, and call handlers registered with watch() if the value has changed.
| Parameter | Type | Description |
|---|---|---|
| name | String | |
| value | anything |
Connect to specified node(s)
| Parameter | Type | Description |
|---|---|---|
| newId | String | String[] | DomNode | DomNode[] |
Sets the style attribute of the widget according to value, which is either a hash like {height: "5px", width: "3px"} or a plain string
Determines which node to set the style on based on style setting in attributeMap.
| Parameter | Type | Description |
|---|---|---|
| value | String | Object |
Attach tooltip to specified node if it's not already connected
| Parameter | Type | Description |
|---|---|---|
| node | OomNode | String |
This method is deprecated, use get() or set() directly.
| Parameter | Type | Description |
|---|---|---|
| name | String | Object | The property to get or set. If an object is passed here and not a string, its keys are used as names of attributes to be set and the value of the object as values to set in the widget. |
| value | Object |
Optional Optional. If provided, attr() operates as a setter. If omitted, the current value of the named property is returned. |
Deprecated, will be removed in 2.0, use this.own(on(...)) or this.own(aspect.after(...)) instead.
Connects specified obj/event to specified method of this object and registers for disconnect() on widget destroy.
Provide widget-specific analog to dojo.connect, except with the
implicit use of this widget as the target object.
Events connected with this.connect are disconnected upon
destruction.
| Parameter | Type | Description |
|---|---|---|
| obj | Object | null | |
| event | String | Function | |
| method | String | Function |
A handle that can be passed to disconnect in order to disconnect before
the widget is destroyed.
var btn = new Button();
// when foo.bar() is called, call the listener we're going to
// provide in the scope of btn
btn.connect(foo, "bar", function(){
console.debug(this.toString());
});
Kick off the life-cycle of a widget
Create calls a number of widget methods (postMixInProperties, buildRendering, postCreate, etc.), some of which of you'll want to override. See http://dojotoolkit.org/reference-guide/dijit/_WidgetBase.html for a discussion of the widget creation lifecycle.
Of course, adventurous developers could override create entirely, but this should only be done as a last resort.
| Parameter | Type | Description |
|---|---|---|
| params | Object | null | Hash of initialization parameters for widget, including scalar values (like title, duration etc.) and functions, typically callbacks like onClick. The hash can contain any of the widget's properties, excluding read-only properties. |
| srcNodeRef | DOMNode | String |
Optional If a srcNodeRef (DOM node) is specified:
|
Wrapper to setTimeout to avoid deferred functions executing after the originating widget has been destroyed. Returns an object handle with a remove method (that returns null) (replaces clearTimeout).
| Parameter | Type | Description |
|---|---|---|
| fcn | Function | Function reference. |
| delay | Number |
Optional Delay, defaults to 0. |
Recursively destroy the children of this widget and their descendants.
| Parameter | Type | Description |
|---|---|---|
| preserveDom | Boolean |
Optional If true, the preserveDom attribute is passed to all descendant widget's .destroy() method. Not for use with _Templated widgets. |
Destroy this widget and its descendants
This is the generic "destructor" function that all widget users should call to cleanly discard with a widget. Once a widget is destroyed, it is removed from the manager object.
| Parameter | Type | Description |
|---|---|---|
| preserveDom | Boolean |
Optional If true, this method will leave the original DOM structure alone of descendant Widgets. Note: This will NOT work with dijit._TemplatedMixin widgets. |
Destroys the DOM nodes associated with this widget.
| Parameter | Type | Description |
|---|---|---|
| preserveDom | Boolean |
Optional If true, this method will leave the original DOM structure alone during tear-down. Note: this will not work with _Templated widgets yet. |
Deprecated, will be removed in 2.0, use handle.remove() instead.
Disconnects handle created by connect.
| Parameter | Type | Description |
|---|---|---|
| handle | undefined |
Used by widgets to signal that a synthetic event occurred, ex:
myWidget.emit("attrmodified-selectedChildWidget", {}).
Emits an event on this.domNode named type.toLowerCase(), based on eventObj. Also calls onType() method, if present, and returns value from that method. By default passes eventObj to callback, but will pass callbackArgs instead, if specified. Modifies eventObj by adding missing parameters (bubbles, cancelable, widget).
| Parameter | Type | Description |
|---|---|---|
| type | String | |
| eventObj | Object |
Optional
|
| callbackArgs | Array |
Optional
|
Get a property from a widget.
Get a named property from a widget. The property may potentially be retrieved via a getter method. If no getter is defined, this just retrieves the object's property.
For example, if the widget has properties foo and bar
and a method named _getFooAttr(), calling:
myWidget.get("foo") would be equivalent to calling
widget._getFooAttr() and myWidget.get("bar")
would be equivalent to the expression
widget.bar2
| Parameter | Type | Description |
|---|---|---|
| name | undefined | The property to get. |
Returns all direct children of this widget, i.e. all widgets underneath this.containerNode whose parent is this widget. Note that it does not return all descendants, but rather just direct children. Analogous to Node.childNodes, except containing widgets rather than DOMNodes.
The result intentionally excludes internally created widgets (a.k.a. supporting widgets) outside of this.containerNode.
Note that the array returned is a simple array. Application code should not assume existence of methods like forEach().
User overridable function that return the text to display in the tooltip.
| Parameter | Type | Description |
|---|---|---|
| node | DomNode |
Returns all the widgets contained by this, i.e., all widgets underneath this.containerNode. This method should generally be avoided as it returns widgets declared in templates, which are supposed to be internal/hidden, but it's left here for back-compat reasons.
Static method to hide the tooltip displayed via showTooltip()
| Parameter | Type | Description |
|---|---|---|
| aroundNode | undefined |
Return true if this widget can currently be focused and false if not
Return this widget's explicit or implicit orientation (true for LTR, false for RTL)
| Parameter | Type | Description |
|---|---|---|
| type | String | Function | protected |
| func | Function |
Display the tooltip; usually not called directly.
| Parameter | Type | Description |
|---|---|---|
| target | DomNode |
Track specified handles and remove/destroy them when this instance is destroyed, unless they were already removed/destroyed manually.
The array of specified handles, so you can do for example:
var handle = this.own(on(...))[0];
Place this widget somewhere in the DOM based on standard domConstruct.place() conventions.
A convenience function provided in all _Widgets, providing a simple shorthand mechanism to put an existing (or newly created) Widget somewhere in the dom, and allow chaining.
| Parameter | Type | Description |
|---|---|---|
| reference | String | DomNode | DocumentFragment | dijit/_WidgetBase | Widget, DOMNode, DocumentFragment, or id of widget or DOMNode |
| position | String | Int |
Optional If reference is a widget (or id of widget), and that widget has an ".addChild" method, it will be called passing this widget instance into that method, supplying the optional position index passed. In this case position (if specified) should be an integer. If reference is a DOMNode (or id matching a DOMNode but not a widget), the position argument can be a numeric index or a string "first", "last", "before", or "after", same as dojo/dom-construct::place(). |
Provides a useful return of the newly created dijit._Widget instance so you can "chain" this function by instantiating, placing, then saving the return value to a variable.
// create a Button with no srcNodeRef, and place it in the body:
var button = new Button({ label:"click" }).placeAt(win.body());
// now, 'button' is still the widget reference to the newly created button
button.on("click", function(e){ console.log('click'); }));
// create a button out of a node with id="src" and append it to id="wrapper":
var button = new Button({},"src").placeAt("wrapper");
// place a new button as the first element of some div
var button = new Button({ label:"click" }).placeAt("wrapper","first");
// create a contentpane and add it to a TabContainer
var tc = dijit.byId("myTabs");
new ContentPane({ href:"foo.html", title:"Wow!" }).placeAt(tc)
Called after the parameters to the widget have been read-in, but before the widget template is instantiated. Especially useful to set properties that are referenced in the widget template.
Kicks off widget instantiation. See create() for details.
| Parameter | Type | Description |
|---|---|---|
| params | Object |
Optional
|
| srcNodeRef | DomNode | String |
Detach tooltip from specified node
| Parameter | Type | Description |
|---|---|---|
| node | DomNode | String |
Set a property on a widget
Sets named properties on a widget which may potentially be handled by a setter in the widget.
For example, if the widget has properties foo and bar
and a method named _setFooAttr(), calling
myWidget.set("foo", "Howdy!") would be equivalent to calling
widget._setFooAttr("Howdy!") and myWidget.set("bar", 3)
would be equivalent to the statement widget.bar = 3;
set() may also be called with a hash of name/value pairs, ex:
myWidget.set({
foo: "Howdy",
bar: 3
});
This is equivalent to calling set(foo, "Howdy") and set(bar, 3)
| Parameter | Type | Description |
|---|---|---|
| name | undefined | The property to set. |
| value | undefined | The value to set in the property. |
Set a property on a widget
Deprecated. Use set() instead.
| Parameter | Type | Description |
|---|---|---|
| attr | String | |
| value | anything |
Static method to display tooltip w/specified contents in specified position. See description of dijit/Tooltip.defaultPosition for details on position parameter. If position is not specified then dijit/Tooltip.defaultPosition is used.
| Parameter | Type | Description |
|---|---|---|
| innerHTML | String | Contents of the tooltip |
| aroundNode | Object | Specifies that tooltip should be next to this node / area |
| position | String[] |
Optional List of positions to try to position tooltip (ex: ["right", "above"]) |
| rtl | Boolean |
Optional Corresponds to |
| textDir | String |
Optional Corresponds to |
| onMouseEnter | Function |
Optional Callback function for mouse over on tooltip |
| onMouseLeave | Function |
Optional Callback function for mouse leave on tooltip |
Deprecated, will be removed in 2.0, use this.own(topic.subscribe()) instead.
Subscribes to the specified topic and calls the specified method of this object and registers for unsubscribe() on widget destroy.
Provide widget-specific analog to dojo.subscribe, except with the implicit use of this widget as the target object.
| Parameter | Type | Description |
|---|---|---|
| t | String | The topic |
| method | Function | The callback |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Returns a string that represents the widget.
When a widget is cast to a string, this method will be used to generate the output. Currently, it does not implement any sort of reversible serialization.
Deprecated. Override destroy() instead to implement custom widget tear-down behavior.
Deprecated, will be removed in 2.0, use handle.remove() instead.
Unsubscribes handle created by this.subscribe. Also removes handle from this widget's list of subscriptions
| Parameter | Type | Description |
|---|---|---|
| handle | Object |
Watches a property for changes
| Parameter | Type | Description |
|---|---|---|
| name | String |
Optional Indicates the property to watch. This is optional (the callback may be the only parameter), and if omitted, all the properties will be watched |
| callback | Function | The function to execute when the property changes. This will be called after the property has been changed. The callback will be called with the |this| set to the instance, the first argument as the name of the property, the second argument as the old value and the third argument as the new value. |
An object handle for the watch. The unwatch method of this object can be used to discontinue watching this property:
var watchHandle = obj.watch("foo", callback);
watchHandle.unwatch(); // callback won't be called now
This is where widgets do processing for when they stop being active, such as changing CSS classes. See onBlur() for more details.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
This is where widgets do processing for when they are active, such as changing CSS classes. See onFocus() for more details.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Despite the name of this method, it actually handles both hover and focus events on the target node, setting a timer to show the tooltip.
| Parameter | Type | Description |
|---|---|---|
| target | DomNode |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Maps on() type parameter (ex: "mousemove") to method name (ex: "onMouseMove"). If type is a synthetic event like touch.press then returns undefined.
| Parameter | Type | Description |
|---|---|---|
| type | String | Function |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Internal method called when this widget is made visible.
See onShow for details.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Handles mouseleave event on the target node, hiding the tooltip.
| Parameter | Type | Description |
|---|---|---|
| target | DomNode |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Called when the widget stops being "active" because focus moved to something outside of it, or the user clicked somewhere outside of it, or the widget was hidden.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of mouse click events.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Called when this widget is being displayed as a popup (ex: a Calendar popped up from a DateTextBox), and it is hidden. This is called from the dijit.popup code, and should not be called directly.
Also used as a parameter for children of dijit/layout/StackContainer or subclasses. Callback if a user tries to close the child. Child will be closed if this function returns true.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of mouse double click events.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Called when the widget becomes "active" because it or a widget inside of it either has focus, or has recently been clicked.
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Called when the tooltip is hidden
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of keys being pressed down.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | key Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of printable keys being typed.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | key Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of keys being released.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | key Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse button is pressed down.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse moves onto this widget.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse moves off of this widget.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse moves over nodes contained within this widget.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse moves off of nodes contained within this widget.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse moves onto nodes contained within this widget.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Connect to this function to receive notifications of when the mouse button is released.
| Parameter | Type | Description |
|---|---|---|
| event | undefined | mouse Event |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});
Called when the tooltip is shown
| Parameter | Type | Description |
|---|---|---|
| target | undefined | |
| position | undefined |
var btn = new Button();
// when /my/topic is published, this button changes its label to
// be the parameter of the topic.
btn.subscribe("/my/topic", function(v){
this.set("label", v);
});