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    <p>So, let's back up and look at what you REALLY have. You already have all the information that you need residing in songs. Why are you in essence duplicating it merely to break out the artist?</p> <p>Think of it this way, if you have the following songs (song/artist)</p> <pre><code>(0) "Death Eater", "Raging Machine Code" (1) "Interrupt", "Raging Machine Code" (2) "Panic", "Times Square Revolution" (3) "New Years", "Times Square Revolution" (4) "Toast", "Ed &amp; Billy's Time Machine" (5) "Surge", "Quiet Cat" (6) "Surveil", "Quiet Cat" </code></pre> <p>What is wrong with this picture? We have the same information duplicated. Ideally, we want to have something like this:</p> <pre><code>"Raging Machine Code" -&gt; has an array that contains "Death Eater" "Interrupt" "Times Square Revolution" -&gt; has an array that contains "Panic" "New Years" "Ed &amp; Billy's Time Machine" -&gt; array that contains "Toast" "Quiet Cat" -&gt; array that contains "Surge" "Surveil" </code></pre> <p>For UITableView this makes things trivial - we tell it how many sections (four) and for each section how many songs. To generate the cell, we get an NSIndexPath that tells us the section and the row (section would be the artist and the row would be the song for that artist).</p> <p>NSTableView doesn't do that. It gives us a row. However, if we do some work on the front end (i.e. the song list) then we can assure that life will be beautiful and fast (or at least faster). The key is to pre-calculate the number of songs per artist and store it.</p> <p>So assume we are asked to display row 5. "Raging Machine Code" is 0-2 (artist, song, song). "Times Square Revolution" is 3-5. Ah! 5 is the last song, so we display "New Years"!</p> <p>Try another one, assume we are to display row 6. "Raging..." was 0-2, "Times..." was 3-5, "Ed &amp; Billy's" is 6-7. Bingo, we need to display the artist, "Ed &amp; Billy's Time Machine"!</p> <p>The idea is that we do much of this prework AHEAD of actually displaying the data. Looping through artists will be far faster than looping through ALL the songs. Plus now you are only doing simple math - no need to move things.</p> <p>Sometimes how you store your data means the difference between success and failure. Whenever you see yourself having to "redefine a data structure" that usually means your data structure is faulty - it may be simple, but it causes more effort.</p> <p>Hopefully this was helpful and didn't end up being "TLTR" (too long to read).</p>
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    1. POCalculating group row at run time of a NSTableView
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    1. COThanks for your answer.You're right, it does run faster by iterating the artists, rather than the songs. But the problem is, that I have to be able to do the same through a filtered song list. So only the songs found by the search should appear in the list..
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    2. COWhat I was showing you was NOT how to iterate through the artists - what I was showing you was how to display the data as required by an NSTableView that didn't require a time consuming spin to reformat the data. What I showed you was how to calculate this at run time (as you originally asked). However to do so, you must store your data differently. BTW this will work on a filtered list too. I guess I'm a little puzzled why this doesn't work for you?
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    3. COI'm trying to understand what you mean.
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