I've a tree-like polymorphic data-structure, where the nodes are instances of class Node (implemented by me) or any its subclass. My application heavily uses Boost and the nodes are actually represented by boost::shared_ptr type rather than Node*
.
Now, I want to create a Qt model to wrap my tree data-structure. Therefore I need a way to associate any model index with a node in my internal data structure. And here comes the problem:
Qt supports two ways of doing it:
First:
QModelIndex QAbstractItemModel::createIndex ( int row, int column, void * ptr = 0 ) const
Creates a model index for the given row and column with the internal pointer ptr.
And second:
QModelIndex QAbstractItemModel::createIndex ( int row, int column, quint32 id ) const
Creates a model index for the given row and column with the internal identifier, id.
Ok, and how exactly should I associate the node in my case? There is no possibility to associate a shared_ptr with the model index... Yes, I know, I can receive a raw pointer from my shared_ptr and supp开发者_高级运维ly it to CreateIndex()
, but it smells bad - seems too unsafe to me.
Any ideas?
By the way, I feel that in general Boost / Qt integration seems to be not trivial at least in the area of memory management.
10x a lot.
If you want to do an easy association without passing a raw pointer, put the shared memory in a container and pass the ID value for that container element into the model index. For example, you could created declare
QMap< quint32, boost::shared_ptr< Foo > > index_map;
and use that. You'd have to be careful to not duplicate IDs for existing pointers, perhaps. It seems somewhat overly complicated to me....
You could also just keep a list of the pointers (to ensure continued availability as you need them) and then use the actual address of the pointer in the QModelIndex
as well. This is probably what I would do.
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