In particular, how to know whether a pointer is actually NULL? I noticed that it's not converted to CL's nil, but a wrapper that contains the NULL pointer inside.

Of course I can hack it by checking whether (format nil "~A" the-pointer) contains the substring null, but I think there should be a better solution.

Thanks in advance!

On Fri, Sep 13, 2013 at 5:39 PM, Rujia Liu <rujia.liu@gmail.com> wrote:

Hi!

I've create a QMessageBox and tried to use clickedButton() to determine which button is clicked, like illustrated in QMessageBox::clickedButton ()'s document.

My function:

(defun yes-no-cancel-dialog (text informative-text yes-text no-text cancel-text)
    (with-objects ((message-box (#_new QMessageBox)))
        (#_setText message-box text)
        (#_setInformativeText message-box informative-text)
        (let ((yes-button (#_addButton message-box yes-text (#_QMessageBox::YesRole)))
              (no-button (#_addButton message-box no-text (#_QMessageBox::NoRole)))
              (cancel-button (#_addButton message-box cancel-text (#_QMessageBox::RejectRole)))
              (clicked-button))
            (#_exec message-box)
            (setf clicked-button (#_clickedButton message-box))
            (format t "clicked:~A~%" (#_clickedButton message-box))
            (format t "clicked:~A~%" yes-button)
            (format t "clicked:~A~%" no-button)
            (format t "clicked:~A~%" cancel-button)
            (cond ((eq clicked-button yes-button) :yes)
                  ((eq clicked-button no-button) :no)
                  ((eq clicked-button cancel-button) :cancel)
                  (t nil)))))

When I click "yes" button, I can see something like:

clicked:#<QPushButton 0x02003E18>
clicked:#<QPushButton 0x02003E18>
clicked:#<QPushButton 0x02004098>
clicked:#<QPushButton 0x02004428>

I tried eq, eql, equal and equalp, none of them return t when comparing clicked-button with yes-button. What can I do to compare two pointers?

Thanks in advance.

- Rujia