iphone - memory leak in uimapkit polyline -

I am practicing drawing polyline on the map. I have adopted the sample code

here is the part when I get a memory warning when I build-> analysis

  MKMapRect routed = MKMapRectMake (SouthWestPoint.x, SouthWestPoint .y , Northwestpoint X. - Southwestpoint.x, North Eastpoint - Southwestpoint. Y); // Clear the allocated memory for the free digit (pointer);  

debugger window prompt error

  '-' left operation is a garbage value  

Oh I don it Did not get it?

Is this a serious error?

How to fix it?

Thank you.

variable northpointpoint apparently not started to do anything This means that your calculation will almost certainly not return whatever you were expecting. You can fix all your variables by starting it in a meaningful position.