Using …Rest to Retrieve Data from XML

I needed a way to get all display object coordinates from XML to support a liquid layout. The XML Data format is specified to mirror the names and hierarchy of the display. The class used to get the data needed to be able to return data from any level in the hierarchy, since the display objects were nested clips.

Other XML getters I have written either expect the path to the data as a literal argument or assume a unique node name at a constant location. In this case I couldn’t provide a literal path argument because the path would differ with each call. The location within the data source could be any number of nodes deep. The end node in each case would be a coordinate value (“X”, “Y”, “Z”, “H”, “L”, “D”) corresponding to a display object attribute, by definition non-unique.

Using the …rest parameter enabled the getter to accept a series of arguments of any length and iterate through them in order to create the path to the data.

public static function getCoordinate( ...clipLevels):Number

Although it isn’t typed, we have to assume that each clipLevels parameter will be an XML node name. A caller looks like this:

private static const scaledSizerX = ContentMeta.getCoordinate("HEADER", "SIZERRADIOGROUP","_SCALEDSIZER","X");

Each string must be in the order [highest to lowest] to build the correct path to the data. A local var [query] stores the result of the highest level query, which is the only one against the data [coordinates_meta].

var query:XMLList = coordinates_meta[clipLevels[0]];

After that, looping through the cliplevels arguments (args = clipLevels.length) against query gets down to the data:

for (var i:uint = 1; i < args; i++)
{

query = query[clipLevels[i]];

}

Then recast the result to a Number and return it to the caller:

returnVal = Number(query[0]);

return returnVal;