when<TResult extends Object?> method

  1. @optionalTypeArgs
TResult when<TResult extends Object?>(
  1. TResult $default(
    1. ElementTheme theme,
    2. Map<String, String>? variables,
    3. Map<String, Map<String, String>>? rules,
    4. ElementAppearanceLabels labels,
    )
)

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( ElementTheme theme,  Map<String, String>? variables,  Map<String, Map<String, String>>? rules,  ElementAppearanceLabels labels)  $default,) {final _that = this;
switch (_that) {
case _ElementAppearance():
return $default(_that.theme,_that.variables,_that.rules,_that.labels);case _:
  throw StateError('Unexpected subclass');

}
}