when<TResult extends Object?> method

  1. @optionalTypeArgs
TResult when<TResult extends Object?>({
  1. required TResult fromString(
    1. String message
    ),
  2. required TResult fromMap(
    1. Json message
    ),
})

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?>({required TResult Function( String message)  fromString,required TResult Function( Json message)  fromMap,}) {final _that = this;
switch (_that) {
case ErrorString():
return fromString(_that.message);case ErrorMap():
return fromMap(_that.message);}
}