DART: indexOf () in the list of instances

Question

How to get the index of a single instance in a list?

class Points { int x, y; Point(this.x, this.y); } void main() { var pts = new List(); int Lx; int Ly; Points pt = new Points(25,55); // new instance pts.add(pt); int index = pts.indexOf(25); // Problem !!! How to obtain the index in a list of instances ? if (index != -1 ){ Lx = lp1.elementAt(index).x; Ly = lp1.elementAt(index).y; print('X=$Lx Y=$Ly'); } 

Answer 1

  // some helper to satisfy `firstWhere` when no element was found var dummy = new Point(null, null); var p = pts.firstWhere((e) => ex == 25, orElse: () => dummy); if(p != dummy) { // don't know if this is still relevant to your question // the lines above already got the element var lx = pts[pts.indexOf(p)]; print('x: ${lx.x}, y: ${lx.y}'); }