What's the best way to find a ID from one QSortFilterProxyModel in another QSortFilerProxyModel?

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Hey,

I would like to know what is the best method to find an ID in a QSortFilerProxyModel? Here is a short example of what I currently have.

My first QSortFilterProxyModel is called "mFungusProxyModel" the second QSortFilterProxyModel is called "mSynonymProxyModel". Now I select an index from the mFungusProxyModel in a QListView. Via

const int id = mFungusProxyModel->data(index.siblingAtColumn(0)).toInt();

I get the ID. Now I want to search this ID in the "mSynonymProxyModel" and get the records, so I can show it in another QListView.

Is there a simple method/way or do I have to create a regular expression that filters this ID?

Christian Ehrlicher

Iterate through your other model and search for the id. Don't know what a regexp should help here though.

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Sorry, I forgot to mention that the mSynonymProxyModel is a 1:N relationship to the mFungusProxyModel. Thereby the possibility exists that the ID occurs several times in the mSynonymProxyModel.

How do I proceed then? I would need something like a "where" clause like "where id = 1" if possible in my ProxyModel and not in the sourceModel.

JonB

@Gabber
If you just need to look up an ID/IDs you could just iterate the table, through the proxy or underlying.

If you are wanting to filter in the proxy for one or more IDs, subclass and override bool QSortFilterProxyModel::filterAcceptsRow(int source_row, const QModelIndex &source_parent) const. Now you can do straight integer comparisons. No need for regular expression. The reg exp is just one way to define a filter in the proxy; it's optional, does nothing if left empty.

eyllanesc

@Gabber If you want to search for an item given the value of a role then a possible option is match method: https://doc.qt.io/qt-5/qabstractitemmodel.html#match

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@JonB
I have no idea how to do this. Maybe you can give me some help. For example, I do not know how to get the ID of both models? Comparing the "numbers" later and returning true or false is also no problem.
I can't do anything with "source_row" and "source_parent" either. What do I have to pass in my mainwindow when I select for example a mushroom in my ListView? Can you give me an example how to do that? The examples on the internet mostly compare "strings" via a pattern.

Let's say I have something like this:

bool CustomSortFilterProxyModel::filterAcceptsRow(int source_row, const QModelIndex &source_parent) const
{
    //What to do here??
    //How do I get the two ID's?
}

It would be nice if someone would show me and explain it.
Thanks for your time.

JonB

@Gabber
You never really replied to @eyllanesc's suggestion. If all you want is to get the list of indexes in a model for a value you could use that.

For mine we are assuming you actually want to filter a model for a particular value in a particular field. You just need to write the desired filterAcceptsRow() implementation in a subclass, and have the outside world tell it which value you want to filter on. So you will want something like the following (you can tidy it):

class SortFilterByIdProxyModel : QSortFilterProxyModel
{
private:
    const int idColumnNumber = 0;
    int idFilterValue = -1;

public:
    void setIdFilterValue(int id)
    {
        if (idFilterValue != id)
        {
            idFilterValue = id;
            emit invalidateFilter();
        }
    }

    bool filterAcceptsRow(int source_row, const QModelIndex &source_parent) const override
    {
        Q_UNUSED(source_parent);    // only tree models use parents, not flat models
        int id = sourceModel()->index(source_row, idColumnNumber).data().toInt();    // get the ID column's value in the source model's source row
        return (id == idFilterValue);    // row accepted iff its id is the desired idFilterValue
    }
}

// Outside world
sortFilterByIdProxyModel->setIdFilterValue(valueDesiredFromOtherModel);

SGaist

@JonB there's a missing call to invalidateFilter in setIdFilterValue.

JonB

@SGaist That was supposed to be the exercise for the user :) I have put it in.

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@SGaist
@JonB

Thank you for the help and support. It works now after the "invalidateFilter" has been added.But so that I also learn something I would like to try the version of @eyllanesc. For this I used the QAbstractItemModel::match function. The code looks like this:

const int id = mFungusProxyModel->data(index.siblingAtColumn(0)).toInt();
QModelIndexList list = mSynonymProxyModel->match(QModelIndex(),Qt::DisplayRole,id);

    QStandardItemModel *myModel = new QStandardItemModel;
    foreach(QModelIndex myIndex, list){
        myModel->setData(myIndex, index.data());
    }

ui->synonymList->setModel(myModel);

Since I haven't found anything on how to get from a QModelIndexList back to a Model and display the whole thing in my QListView, I thought I'd create a QStandardItemModel, iterate over the List and add the data to the Model. Unfortunately, I only have an empty QListView. But now I don't know if it's because of my QModelIndexList, because I use an empty QModelIndex() as start index or what the problem could be. For tips I would be very grateful again.

This is my first QT project so I still have a lot to ask and learn.

JonB

@Gabber said in What's the best way to find a ID from one QSortFilterProxyModel in another QSortFilerProxyModel?:

myModel->setData(myIndex, index.data());

Check setData()'s return value, it should be false. You can't do this! myIndex is an index into mSynonymProxyModel, you can't use that to index into myModel!

Either you have to use the result of the match() as indexes into mSynonymProxyModel, or you would have to copy the data into your new QStandardItemModel.

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@JonB

Okay, I am now ready to get to my names. I'm just not sure how to tell the ProxyModel (in my case mSynonymProxyModel) to show me only the records from the QModelIndexList. Can you please explain this to me?

My code looks like this:

    const int id = mFungusProxyModel->data(index.siblingAtColumn(0)).toInt();
    QModelIndex mIndex = mSynonymProxyModel->index(0,2);
    QModelIndexList list = mSynonymProxyModel->match(mIndex,Qt::DisplayRole,id, -1);

    foreach(QModelIndex myIndex, list){
        auto test = myIndex.siblingAtColumn(1).data();
        mSynonymProxyModel-> // What to do here, to set only the data from list
    }

SGaist

Call setData with the index you got and whatever data you want to put there.

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@SGaist

I already tried that, but when I then add the mSynonymProxyModel to the QListView again, all the data from my ProxyModel is displayed and not just the one from the QModelIndexList. Do I need to do anything else? My code looks like this:

    foreach(QModelIndex myIndex, list){
        auto test = myIndex.siblingAtColumn(1).data(); //only for debuging
        mSynonymProxyModel->setData(myIndex, myIndex.data());
    }

ui->synonymList->setModel(mSynonymProxyModel);

SGaist

Sorry, I misunderstood your intentions.

As @JonB already wrote, you would need to build a new model with the match result data.

Wasn't the proxy supposed to be the model to feed the synonym view ?

JonB

@JonB said in What's the best way to find a ID from one QSortFilterProxyModel in another QSortFilerProxyModel?:

@Gabber
You never really replied to @eyllanesc's suggestion. If all you want is to get the list of indexes in a model for a value you could use that.
For mine we are assuming you actually want to filter a model for a particular value in a particular field

It seems to me using match() is not what you are looking to do here. Given that you do want to filter, and you had that way working earlier, I don't think you're pursuing anything useful.

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This post is deleted!

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@JonB
Your code works very well, thank you! I have one more question though: Is there a nicer way to filter by a specific ID or output all records? My code for this looks like this. Of course I always have to setFilterId(-1) which I don't like so much.

void FungusSortFilterProxyModel::setIdFilter(const int &id)
{
    if(mIdFilterValue != id)
    {
        mIdFilterValue = id;
        emit invalidateFilter();
    }
}

bool FungusSortFilterProxyModel::filterAcceptsRow(int source_row, const QModelIndex &source_parent) const
{
    if(mIdFilterValue == -1){
        return true;
    } else {
        Q_UNUSED(source_parent);
        const int id = sourceModel()->index(source_row, mIdColumNumber).data().toInt();
        return (id == mIdFilterValue);
    }
}

JonB

@Gabber said in What's the best way to find a ID from one QSortFilterProxyModel in another QSortFilerProxyModel?:

Is there a nicer way to filter by a specific ID or output all records?
Of course I always have to setFilterId(-1) which I don't like so much.

I don't know what you are looking for/what is wrong with what you have/what you would rather have?! What is the objection? If there is a valid mIdFilterValue you compare it against each row, but if it is invalid you don't bother and just return true. Seems fine to me?

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@JonB

I just wanted to know if there is a programming possibility to implement filterAcceptsRow in such a way that all records are always output and only when I call setIdFilter(id), it is filtered by this ID. After that all records should be used again automatically. If this is too complex or not possible then I have to work with setIdFilter(-1).