Consider a function in Dart file
void myFunction({int input = 1, Function(int, String) callback}) {
// ...
}
So, I wonder is it possible at all to specify a default value for the callback
parameter, for instance it can be something like (_, _) => { }
.
PS I know it has null
as default value and ??
can help to avoid NPE
, I'm just curious is it possible at all. Cheers.
You can do something like:
dynamic func(int i, String s) {
print(i.toString() + s);
}
void myFunction({int input = 1, Function(int, String) callback = func}) {
callback(input, " .");
}
void main() {
myFunction(input: 2);
}
The default value of an optional parameter must be constant.
This is what the documents said
This thing can be bypassed like this:
dynamic myCallback(int a,String b) {
}
void myFunction({int input = 1, Function(int, String) callback }) {
if (callback == null) callback = myCallback;
}
Edit:
Alternatively, you can use anonymos functaion with out myCallback
funcation like this:
void myFunction({int input = 1, Function(int, String) callback }) {
if (callback == null) callback = (a,b){};
}
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