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POEfficient way to manage item positions in grid after rotation/flip in iOS
 

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  1. POEfficient way to manage item positions in grid after rotation/flip in iOS
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    <p>I am looking for some guidance on the most efficient way to design a class to manage the position of 3 items in a 6x6 grid. The items on the grid cannot move/change their position, however, the entire grid can be rotated in 90-degree increments clockwise/counter clockwise and can be flipped horizontally/vertically based on user touch/drag manipulations of the grid in realtime on iOS devices. As a result of rotating and/or flipping the entire grid, the 3 items in the grid will be in different “absolute” positions based on a non-rotated “position reference” grid. It is these new item positions I am trying to determine in the most efficient manner after each “transform” of the grid.</p> <p>To illustrate what I am trying to accomplish, consider the following... I am numbering the positions in the grid where the upper-left corner is position 0 and numbers increment to the right then down:</p> <p>Position Reference Grid:</p> <pre><code>------------------------- | 0 | 1 | 2 | 3 | 4 | 5 | ------------------------- | 6 | 7 | 8 | 9 | 10| 11| ------------------------- | 12| 13| 14| 15| 16| 17| ------------------------- | 18| 19| 20| 21| 22| 23| ------------------------- | 24| 25| 26| 27| 28| 29| ------------------------- | 30| 31| 32| 33| 34| 35| ------------------------- </code></pre> <p>I am planning to always refer to an item's position in the grid using this numbering regardless of any rotation/flip transform applied to the grid. So, for example, if I have items in positions A=7, B=9, C=14 </p> <p>Original:</p> <pre><code>------------------------- | 0 | 1 | 2 | 3 | 4 | 5 | ------------------------- | 6 | A | 8 | B | 10| 11| ------------------------- | 12| 13| C | 15| 16| 17| ------------------------- | 18| 19| 20| 21| 22| 23| ------------------------- | 24| 25| 26| 27| 28| 29| ------------------------- | 30| 31| 32| 33| 34| 35| ------------------------- </code></pre> <p>and rotate the grid 90 degrees clockwise, the new item positions will be A=10, B=22, C=15. </p> <p>Rotated Clockwise 90 degrees:</p> <pre><code>------------------------- | 0 | 1 | 2 | 3 | 4 | 5 | ------------------------- | 6 | 7 | 8 | 9 | A | 11| ------------------------- | 12| 13| 14| C | 16| 17| ------------------------- | 18| 19| 20| 21| B | 23| ------------------------- | 24| 25| 26| 27| 28| 29| ------------------------- | 30| 31| 32| 33| 34| 35| ------------------------- </code></pre> <p>There are just 8 possible orientations of the grid (0, 90, 180, 270 degrees on each side), so each item has exactly 8 known positions based on the orientation of the grid. As such, I could hard-code 8, 3-item arrays containing the absolute positions of the 3 items for each of the 8 orientations – one array per orientation. Once I know what orientation the grid is in after some transform, I can simply grab the correct 3-item array of item positions that corresponds to the grid orientation to get the new positions of the 3 items. </p> <p>Since I need to do this position retrieval for several grids at a time, since the grid transforms are in direct response to touch manipulations on iOS, and since there may be more items in the grids, I am wondering if such hard-coding is the way to go or if there is some more elaborate way to calculate or otherwise dynamically determine the position of the items in the grid once a rotation or flip of the grid has occurred.</p> <p>Any advice, comments, suggestions are greatly appreciated.</p> <p>Thanks in advance!</p>
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