final ValueSetter<int> setVal;
can be assigned a function callback that accepts one parameter like
setVal=(i){
//assign i to some variable
}
What if I wanted the callback to accept 2 parameters like
setVal=(i,j){
//assign i and j to some variable
}
?
Variables of type Function can be declared as follows:
void main() {
void Function(int) setVal1;
void Function(int, int) setVal2;
setVal1 = (int i) => print('$i');
setVal2 = (int i, int j) => print('$i, $j');
final String Function(int, int, [double]) setVal3 =
(int i, int j, [double k]) => '$i, $j, $k';
final i = 0;
final j = 1;
final double k = 2.0;
setVal1(i);
setVal2(i, j);
print(setVal3(i, j));
print(setVal3(i, j, k));
}
How to declare a function callback(s) that accepts multiple parameters in Dart/Flutter. Including an additional answer to the question asked in the comments about how to make the second parameter optional. Yeah...ValueSetter is typedef'ed as:
typedef ValueSetter<T> = void Function(T value);
As in, a function that takes one parameter. So, no, you can't hand it a function that takes two parameters.
final Function(int, String) = (int a, String b){
/* do stuff */
}
Just put whatevery you want in a map and pass the map. Something like this:
Map<String, dynamic> updateMap = {
'id': id,
'value': value
widget.onUpdate(updateMap);
You can declare your own type, just add this def in your helpers.dart file:
typedef ValueSetter2<T, E> = void Function(T value, E value2);
