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remove WStandardItemModel row and append row to same WStandardItemModel??

Added by Mark Travis over 1 year ago

I'm trying to take a row out of a WStandardItemModel and append it to the end of the WStandardItemModel. ie, take row 5 out of a 100 row table, and append that row so that it becomes the new row 100.

Can this be done? 

 std::vector<std::unique_ptr<Wt::WStandardItem>> rowToMove;
 rowToMove = shadowCopyItemModel->takeRow(i);
 shadowCopyItemModel->appendRow(rowToMove);

I tried the following first, but that didn't work. Probably too much for all the templating to handle. 

shadowCopyItemModel->append(shadowCopyItemModel->takeRow(i));

I'm getting an error that says:
In instantiation of member function 'std::vectorstd::unique_ptr>::vector' requested here.

I'm not sure what the extra "::vector" in the error message is referring to.


Replies (4)

RE: remove WStandardItemModel row and append row to same WStandardItemModel?? - Added by Mark Travis over 1 year ago

I added std::move to the append, but I'm now getting an EXC_BAD_ACCESS while the widget tries to update the tableview and viewwidgets.

Seems like this should be the same mechanism as the sort routines, right?

RE: remove WStandardItemModel row and append row to same WStandardItemModel?? - Added by Roel Standaert over 1 year ago

I tried to reproduce your issue, but this code seems to run perfectly fine:

#include <Wt/WAny.h>
#include <Wt/WStandardItem.h>
#include <Wt/WStandardItemModel.h>

#include <memory>

constexpr int ROW_COUNT = 100;

int main()
{
  auto model = std::make_shared<Wt::WStandardItemModel>();
  for (int i = 0; i < ROW_COUNT; ++i) {
    model->appendRow(std::make_unique<Wt::WStandardItem>(Wt::utf8("Row {1}").arg(i)));
  }

  model->appendRow(model->takeRow(20));

  for (int i = 0; i < model->rowCount(); ++i) {
    std::cout << i << ": " << Wt::asString(model->data(i, 0)).toUTF8() << '\n';
  }
}

RE: remove WStandardItemModel row and append row to same WStandardItemModel?? - Added by Mark Travis over 1 year ago

Thanks Roel!

I just fixed this late last night.

To get around the perceived reason for the bug, I added:

        Wt::WApplication::instance()->deferRendering();
        Wt::WApplication::instance()->resumeRendering();

before and after the block.

I was debugging and was getting a nullptr on Wt::Application::instance(), which seemed to be the source of all.

Then I realized I was in the data prep phase at the beginning of a spawned thread where I'm using the WStandardItemModel as a mechanism to slice, dice, and manipulate the data before exporting it to a matrix for processing.

Instead of figuring out a way to block from another thread (which you had mentioned to me in another post), I realized I could move the block before the thread call back into the main loop, where it works perfectly now.

RE: remove WStandardItemModel row and append row to same WStandardItemModel?? - Added by Mark Travis over 1 year ago

The second "block" of that last sentence I mean "code block" instead of "blocking the updates". Sorry, should have finished my coffee before posting. :)

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