HERE Maps API - Short introduction to observable lists
The OList class in Nokia Maps API is used to provide an observable list. In this article we show how to create the list and how to perform some operations on it.
new nokia.maps.util.OList ([elements])
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Prerequisites
Nokia Maps API supported web browser (basically any modern web browser)
Important note about maps credentials
Nokia provides several services options within the Maps API offering. The service is free to use, but you must obtain and use authentication and authorization credentials to use the services. Please read the Location API Business Models and Usage Restrictions page to decide which business model best fits your needs. Authentication requires unique Maps API credentials, namely an AppId and a token. You can get these credentials free from the Nokia Developer API Registration page.
Implementation
The list can be manipulated by adding and removing items on it, and queries can be performed for e.g. the length of the list.
To create a new list:
mylist = new nokia.maps.util.OList();
To add to the list (e.g. three coordinates)
mylist.add([53.1]);
mylist.add([13.1]);
mylist.add([23.1]);
Query the length of a list:
mylist.getLength();
This would return amount of "3" items as its result.
To clear the list from items:
mylist.clear()
The result of getLength() for the list would return zero/no items:
mylist.getLength();
The list can be enabled with an Observer.
addObserver (callback, [context])
To register a new observer.
API Reference definition:
Parameters: {Function} callback The callback which will be invoked after the list was modified with following arguments: (OList) oList - the OList instance itself (String) method - the name of the method which caused the triggering (Variant) element - the element which was added or deleted (Number) idx - the index of the concerned element
The callback can signalize that a rollback has occurred by returning true.
{Object} [context]: The context to use when the callback will be invoked.
Example code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Observable Lists</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript"
src="http://api.maps.nokia.com/2.2.1/jsl.js" charset="utf-8">
</script>
</head>
<body>
<div id="mapContainer" style="z-index: -1; left:0px; top:0px; width: 100%; height: 80%; position: absolute;"></div>
<script type="text/javascript">
/////////////////////////////////////////////////////////////////////////////////////
// Don't forget to set your API credentials
//
// Replace with your appId and token which you can obtain when you
// register on http://api.developer.nokia.com/
//
nokia.Settings.set( "appId", "YOUR APP ID GOES HERE");
nokia.Settings.set( "authenticationToken", "YOUR AUTHENTICATION TOKEN GOES HERE");
//
/////////////////////////////////////////////////////////////////////////////////////
var map = new nokia.maps.map.Display(document.getElementById("mapContainer"), {
components: [
//behavior collection
new nokia.maps.map.component.Behavior(),
new nokia.maps.map.component.ZoomBar(),
new nokia.maps.map.component.Overview(),
new nokia.maps.map.component.TypeSelector(),
new nokia.maps.map.component.ScaleBar() ],
zoomLevel: 10,
center: [52.51, 13.4]
});
mylist = new nokia.maps.util.OList();
mylist.add([53.1]);
mylist.add([13.1]);
mylist.add([23.1]);
alert("Length of the list: "+mylist.getLength());
mylist.addObserver (listModified);
mylist.add([53.1]);
//Comment this out to test the listener
function listModified()
{
alert("List was modified!");
alert("Length of the list: "+mylist.getLength());
}
</script>
</body>
</html>
For more on Nokia Maps API
Please check out the Nokia Maps API full documentation and API reference here:
You may also access the interactive Nokia Maps API playground,
