Iterating an object and erasing members

[awolff64]

I assumed the object works like an std::map and learned that the container is a vector.
This cause the following code to fail

auto it = m_Data.object_range().begin();
while (it != m_Data.object_range().end())
{
	if (lw::util::general::MatchText(it->name(), Key, true))
	{
		auto tmp = it;

		it++;
		// it now points to the successor of the to be erased element
		m_Data.erase(tmp);
		// tmp is now invalid
		continue;
	}
	it++;
}

If I have to erase the member I copy the iterator to tmp and increment the iterator. This is to ensure that it points to a valid element after erase.
This did not work as the object's container is a vector. To get it working I do not increment the iterator when I erase. After the ease the it already points to the next object.

auto it = m_Data.object_range().begin();
while (it != m_Data.object_range().end())
{
	if (lw::util::general::MatchText(it->name(), Key, true))
	{
		m_Data.erase(it);
		// it now points to the successor of the erased element
		continue;
	}
	it++;
}

Having a solution is fine.
However I would prefer being agnostic to the underlying container.

Is there a better way to get this working?
E.g. if erase would return the iterator to the next element (as std::vector::erase does, but not std::map::erase).

[danielaparker]

Yes, jsoncons uses flat-map semantics, currently using std::vector as underlying storage. This should be more prominently documented.

I think

m_Data.erase(it);
// it now points to the successor of the erased element

is actually undefined behavior, I think it should be

it = m_Data.erase(it);

except the jsoncons erase function returns void. We'll fix that in a patch, after which it should be written as above.

Daniel

[danielaparker]

This change has been made on master, the basic_json::erase function return value, previously void, is now an iterator following the last removed element,

array_iterator erase(const_array_iterator pos);
object_iterator erase(const_object_iterator pos);

array_iterator erase(const_array_iterator first, const_array_iterator last); 
object_iterator erase(const_object_iterator first, const_object_iterator last);

Incidentally, instead of it->name(), use it->key(), name() was deprecated a long time ago, that should have resulted in a warning. To be sure that you're not using any deprecated functions, you may want to define the JSONCONS_NO_DEPRECATED macro.