QAbstractItemModel::beginInsertRows: what happens if the insert fails?

Question

Qt

In a descendant of QAbstractItemModel , the insert function may say: insert is not possible for some reason. We do not throw out accidents, we check error codes.
1. How will endInsertRows behave in such a situation?
2. Is it possible to change data classes outside of beginInsertRows/endInsertRows and do nothing between these functions?
3. And if both are not available, what is the best insert architecture to come up with?

Answer 1

So far I've come up with this design...

class Committer {  // interface
public:
  virtual void commit() = 0;
  virtual ~Committer() = default;
}

enum class ErrCode { OK, UNCLONEABLE, BAD_RECIPIENT };

struct CommitObj {
  ErrCode errCode;
  std::unique_ptr<Committer> action;
}

class UiObj {
public:
  virtual CommitObj startClone(std::shared_ptr<UiObj> recipient) = 0;
}

We either get an object for which it is sufficient to give commit() in a protected block, or a reason why cloning is not possible.

Answer 2

What problem are you trying to solve?
beginInsertRows/endInsertRows are needed to notify views about insertion.
It's hard for me to imagine a situation in which you called beginInsertRows but failed to insert data. If there are concerns, you can check the data in advance and only then insert them.