Method insert

src/react/properties.py:76–80

(self, i: int, item: _T)

            observer.on_add(item, len(self.data) - 1)

    def insert(self, i: int, item: _T) -> None:
        super().insert(i, item)

        for observer in self._observers:
            observer.on_add(item, i)

    def pop(self, i: int = ...) -> _T:
        item = super().pop(i)