Something went wrong after switching from 5.12 to 5.13. Probably I selected a wrong configuration 'VS2017 Desktop 64bit'. If I select 'Desktop Qt 5.13 MSVS2017 64bit' the project compiles.
By doing it ? Note your indentation is all over the place so it is a bit hard to determine within what you have defined these methods. Going with the assumption that all the methods are directly under the class here is how
Methods in the same class share the same "self" indicator but if they were not in the same class (or embedded deeper under another method) then you would need to use the handle to the method via its class and/or parent method
Well without seeing a minimal fully functioning example of your code it is kind of hard to guess what you might be doing wrong.
However as a general answer I (unless the combo box has a large amount of data in it) just store this data in dictionary and/or list and then add to the dictionary/list -- purge the combo box -- and add the data pre-sorted back into the combo box
Yes the basic question should be not "How do I remove duplicates from a table view" but more "How do I stop from putting duplicates into a table view". Keep in mind the latter is actually much easier than the former and is the proper methodology. Duplicates (if not desired) should never be allowed into the table view to begin with. If they are getting there then the onus is on the procedures that are responsible for adding data to the table view and that is where you need to fix your code. There are numerous ways to do this one of which has already been suggested. Still the best way for you would be to post your minimal fully functioning code so we can help you redesign it to work properly.