Mixin
O.ObservableRange
The ObservableRange mixin adds support for observing an (integer-based) numerical range of keys to an observable object. The object is expected to have the ObservableProps mixin applied and have a length property.
"use strict";
( function ( NS, undefined ) {
var meta = NS.meta;
NS.ObservableRange = {Method
O.ObservableRange#rangeDidChange( start, end )
Notifies observers that are observing a range which intersects the range
that has changed. Also notifies any observers observing an individual
number (via O.ObservableProps#addObserverForKey) and any observers
looking out for a change to [] (enumerable content did change).
Parameters
| start | Number The index of the first value in the range to have changed (indexed from 0). |
|---|---|
| end | Number The index of one past the last value in the range to have changed. |
Returns
O.ObservableRange Returns self.
rangeDidChange: function ( start, end ) {
if ( end === undefined ) { end = start + 1; }
var metadata = meta( this ),
key, index;
for ( key in metadata.observers ) {
index = parseInt( key, 10 );
if ( start <= index && index < end ) {
this.propertyDidChange( key );
}
}
var observers = metadata.rangeObservers,
l = observers ? observers.length : 0,
enumerableLength = this.get( 'length' ) || 0;
while ( l-- ) {
var observer = observers[l],
range = observer.range,
observerStart = range.start || 0,
observerEnd = 'end' in range ?
range.end : Math.max( enumerableLength, end );
if ( observerStart < 0 ) { observerStart += enumerableLength; }
if ( observerEnd < 0 ) { observerEnd += enumerableLength; }
if ( observerStart < end && observerEnd > start ) {
observer.object[ observer.method ]( this, start, end );
}
}
this.computedPropertyDidChange( '[]' );
return this;
},Method
O.ObservableRange#addObserverForRange( range, object, method )
Registers an object and a method to be called on that object whenever an integer-referenced property in the given range changes. Note, the range is 'live'; you can change the start/end values in the object at any time and immediately receive notifications of updates in the new range. Negative values for start or end are allowed, and are treated as offsets from the end of the current length of this object, with -1 being the last item.
Parameters
| range | Object The range to observe. May have either, both or none of start and end properties. These are numerical values, indexed from 0, negative values index from the end of the enumerable object. If start is omitted it is taken to be 0 (the first element in the enumerable). If end is ommitted it is taken to be the length of the enumerable. start is inclusive and end is exclusive, e.g. {start: 1, end: 2} will only fire if index 1 changes. |
|---|---|
| object | Object The object on which to call the callback method. |
| method | String The name of the callback method. |
Returns
O.ObservableRange Returns self.
addObserverForRange: function ( range, object, method ) {
var metadata = meta( this );
( metadata.rangeObservers || ( metadata.rangeObservers = [] ) ).push({
range: range,
object: object,
method: method
});
return this;
},Method
O.ObservableRange#removeObserverForRange( range, object, method )
Stops callbacks to an object/method when content changes occur within the range. Note, the range object passed must be the same as that passed for addObserverForRange, not just have the same properties (these could have changed due to the support for live updating of the observed range. See O.ObservableRange#addObserverForRange description).
Parameters
| range | Object The range which is being observed. |
|---|---|
| object | Object The object which is observing it. |
| method | String The name of the callback method on the observer object. |
Returns
O.ObservableRange Returns self.
removeObserverForRange: function ( range, object, method ) {
var observers = meta( this ).rangeObservers,
l = observers ? observers.length : 0;
while ( l-- ) {
var observer = observers[l];
if ( observer.range === range &&
observer.object === object && observer.method === method ) {
observers.splice( l, 1 );
break;
}
}
return this;
}
};
}( O ) );