Get the index of an item from QTreeView

[vijaychsk]

Hi,
I have a QTreeView that is working fine. Separate from this view, I have another QRegLineEdit widget where users can search using a full hierarchical path (like top.U1 or top.U3.U3_1 or top.U4.U4_1_1) and I display properties to that path. It is also working fine because both are independent of each other which means QRegLineEdit doesn't depend on any data from QTreeModel.

However, I now want to connect QRegLineEdit and QTreeView. Whenever a user enters a path, I perform some basic checks on whether the input is right or wrong and then I would like to highlight or scroll to that hierarchy/parent in the QTreeView.

How do I do that reverse lookup? If I have the index of the item in the QTree then I can do the scrollTo method to go to that item. I just don't know how to get the index from a string.

It is to be noted that I cannot simply search for a child say U4_U4_1_1 because it can exist under different parents (duplicates possible) but the full hierarchical path is unique.

top
    -- U1
    -- U2
    -- U3
         -- U3_1
         -- U3_2
    -- U4
         -- U4_1
              -- U4_1_1
              -- U4_1_2
    -- U5

[Kent-Dorfman]

One way is to keep a lookup table/map where the path is the key, and the pointer to the tree leaf/node is the data.

[jeremy_k]

QAbstractItemModel::match() is worth a look.

[JonB]

@vijaychsk
You could keep a "lookup table/map" as @Kent-Dorfman says. But potentially that could be "costly" to maintain, especially if the tree is large/deep.

There are two ways you can do it just from the information already held in the tree model.

• Do like QFileSystemModel does it. It defines a role QFileSystemModel::FilePathRole Qt::UserRole + 1. That role returns the full file path from each node/leaf. You can then search for this full path (e.g. via @jeremy_k's QAbstractItemModel::match()). This is simple but "expensive": the tree does a lot of looking back up at parentage (unless you do some extra work) to generate each item's full path to compare.

• Just look down the tree for each element in turn from the desired path. For example, if looking for /a/b/c, first find a at top-level, then b among its children, and finally c among b's children. You could do that easily yourself from model's nodes' children, or maybe from QAbstractItemModel::match() without the Qt::MatchRecursive flag being set in Qt::MatchFlags flags.