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POPattern to update a UItableView and its datasource after filtering with NSPredicate
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copied!<p>This seems like it should be straight forward. Technically I can make this work, but if I want to perform certain UI animations, (using deleteRowsAtIndexPaths:withRowAnimation:) things get hairy. It seems as though the datasource and UI are fighting over who should delete first. Then I have to artificially keep data around for the UI update.</p> <p>My current setup:</p> <p>In my model:</p> <ol> <li>Create a multidimensional NSArray to hold my data. (each sub array represents a section).</li> <li>Place a NSDictionary in each section array to represent the data for an individual cell.</li> </ol> <p>In my View Controller:</p> <ol> <li>Create a multidimensional NSArray to hold my Cell Controllers (mimicking the data structure).</li> <li>Assign each model dictionary to an ivar in the appropriate Cell Controller.</li> <li>Hook up the data to the cell</li> </ol> <p>This gets my UITableView on screen with cells properly displayed. Now if I want to filter the data in the table I do the following:</p> <p>In my model:</p> <ol> <li>Create an instance of NSPredicate.</li> <li>Filter each subarray of the multidimensional array.</li> <li>Set a flag in each dictionary that is within the results of the filtered array.</li> </ol> <p>In my View controller:</p> <ol> <li>I create a new Multidimensional NSArray. This array will hold the cell controllers of the "filtered data"</li> <li>Loop through the current Multidimensional Controller array. Add it to the new "filtered array if it's model's flag is set.</li> <li>Replace the unfiltered Controller array with the new one.</li> <li>Update the table.</li> </ol> <p>This also works very well. As long as I don't mind the UI updating instantaneously. If I want to delete rows with animation, I must pass those indexes to the table to be deleted.</p> <p>To accomplish this, I add a few more steps to the view controller:</p> <p>In my View controller:</p> <ol> <li>I create a new Multidimensional NSArray. This array will hold the cell controllers of the "filtered data"</li> <li>Loop through the current Multidimensional Controller array. Add it to the new "filtered array if it's model's flag is set.</li> <li>Create a new NSArray to hold indexes to be deleted.</li> <li>Loop through the current Multidimensional Controller array. Add its cell's index to the "toBeDeleted" array if its model's flag is NOT set.</li> <li>Replace the unfiltered Controller array with the new one.</li> <li>perform deleteRowsAtIndexPaths:withRowAnimationn.</li> </ol> <p>So far this method doesn't work the greatest. I am having issues deleting the rows with edge cases (empty sections and all visible cells being deleted).</p> <p>This made me think maybe my methodology is flawed. Has anyone implemented this in an app? How did you solve this? Do your row animations work?</p>

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