noSuchMethod method Null safety
- Invocation invocation
Invoked when a non-existent method or property is accessed.
A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:
dynamic object = 1;
object.add(42); // Statically allowed, run-time error
This invalid code will invoke the noSuchMethod method
of the integer 1 with an Invocation representing the
.add(42) call and arguments (which then throws).
Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.
A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:
class MockList<T> implements List<T> {
noSuchMethod(Invocation invocation) {
log(invocation);
super.noSuchMethod(invocation); // Will throw.
}
}
void main() {
MockList().add(42);
}
This code has no compile-time warnings or errors even though
the MockList class has no concrete implementation of
any of the List interface methods.
Calls to List methods are forwarded to noSuchMethod,
so this code will log an invocation similar to
Invocation.method(#add, [42]) and then throw.
If a value is returned from noSuchMethod,
it becomes the result of the original invocation.
If the value is not of a type that can be returned by the original
invocation, a type error occurs at the invocation.
The default behavior is to throw a NoSuchMethodError.
Implementation
@override
dynamic noSuchMethod(Invocation invocation) {
// Note: This solution is only valid on Flutter 3.3 / Dart 2.18
//
// On the Web platform, the [DateTime.difference] method reads the `other._value` variable internally.
// ConstDateTime does not have a `_value` variable, which leads to errors when running
// Returning [millisecondsSinceEpoch] in this case will prevent the error from being reported.
//
// @see https://github.com/dart-lang/sdk/blob/56e581aa3415858bbaf22bee23be705a68f8a03e/sdk/lib/_internal/js_runtime/lib/core_patch.dart#L342
if (_kIsWeb && invocation.isGetter && !invocation.isSetter
// Flutter web performs minified in release mode, resulting in not getting the correct memberName.
/* && invocation.memberName == #_value */) {
return dateTime.millisecondsSinceEpoch;
}
return super.noSuchMethod(invocation);
}