when<TResult extends Object?> method

  1. @optionalTypeArgs
TResult when<TResult extends Object?>(
  1. TResult $default(
    1. double scrollOffsetX,
    2. double scrollOffsetY,
    3. double viewportWidth,
    4. double viewportHeight,
    5. int firstVisibleRow,
    6. int lastVisibleRow,
    7. int firstVisibleColumn,
    8. int lastVisibleColumn,
    )
)

A switch-like method, using callbacks.

As opposed to map, this offers destructuring. It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case Subclass2(:final field2):
    return ...;
}

Implementation

@optionalTypeArgs TResult when<TResult extends Object?>(TResult Function( double scrollOffsetX,  double scrollOffsetY,  double viewportWidth,  double viewportHeight,  int firstVisibleRow,  int lastVisibleRow,  int firstVisibleColumn,  int lastVisibleColumn)  $default,) {final _that = this;
switch (_that) {
case _ViewportState():
return $default(_that.scrollOffsetX,_that.scrollOffsetY,_that.viewportWidth,_that.viewportHeight,_that.firstVisibleRow,_that.lastVisibleRow,_that.firstVisibleColumn,_that.lastVisibleColumn);case _:
  throw StateError('Unexpected subclass');

}
}