KeySet<T extends KeyboardKey> constructor
Null safety
- T key1,
- [T? key2,
- T? key3,
- T? key4]
A constructor for making a KeySet of up to four keys.
If you need a set of more than four keys, use KeySet.fromSet.
The same KeyboardKey may not be appear more than once in the set.
Implementation
KeySet(
T key1, [
T? key2,
T? key3,
T? key4,
]) : assert(key1 != null),
_keys = HashSet<T>()..add(key1) {
int count = 1;
if (key2 != null) {
_keys.add(key2);
assert(() {
count++;
return true;
}());
}
if (key3 != null) {
_keys.add(key3);
assert(() {
count++;
return true;
}());
}
if (key4 != null) {
_keys.add(key4);
assert(() {
count++;
return true;
}());
}
assert(_keys.length == count, 'Two or more provided keys are identical. Each key must appear only once.');
}