GDirections 25 element limit

There’s an undocumented feature in the Google Maps API when retrieve driving direction wherein any GDirections request with more than 25 elements returns an error with code G_GEO_BAD_REQUEST (400). This isn’t particularly helpful but I found the answer in the Google Maps forums somewhere. So the trick is to partition your array of waypoints into 25 part segments. Using Prototype 1.5 this is really simple using the inGroupsOf method, however using earlier Prototype versions is a little more tricky. I’m including a function that can do it with either.

function doDirections(elements) {

  var mapLimit = 25;
  elements = $A(elements);
  var groups = null;
  if('inGroupsOf' in elements) {
    groups = elements.inGroupsOf(mapLimit);
  } else {
    groups = [];
    var tempGroup = [];
    elements.each(function(point, index) {
      if(index == mapLimit) {
        groups.push(tempGroup);
        tempGroup = [];
      }
      tempGroup.push(point);
    }
  }

  groups.each(function(i) {
    var direction = new GDirections();
    //Insert your options for directions objects here.
    direction.loadFromWaypoints(i);
  }
}

posted by Michael Gall at 10:08 am & tagged with Tags: code, gdirections, google maps, javascript | 2 Comments »