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POUsing NSCache as data source for pickerview may crash
 

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  1. POUsing NSCache as data source for pickerview may crash
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    <p>I have some data that was originally stored in sqlite and will be loaded to NSCache when first used. I copy the data from NSCache to a pickerview object and use the data to generate pickerview("retain" in the object).</p> <p>However, a small amount of users encounter crashes because the data in pickerview object is not as expected.</p> <p>Datasource.m:</p> <pre><code>- (NSDictionary *)getAllCurrenciesForCache { NSData *data = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"CurrencyList" ofType:@"json"]]; NSDictionary *dict = [data objectFromJSONData]; return dict; } - (NSArray *)getCurrencyList { NSDictionary *currencies = [cache objectForKey:@"key"]; if(!currencies){ NSDictionary *currencies = [self getAllCurrenciesForCache]; [cache setObject:currencies forKey:@"key"]; } NSArray *keys = [currencies allKeys]; if(keys){ // do some sorting return [keys sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)]; } // shouldn't be here return nil; } </code></pre> <p>ViewController.m:</p> <pre><code> NSArray *data = [datasource getCurrencyList]; NSMutableArray *currencies = [[NSMutableArray alloc] init]; for (NSString *abbr in data) { [currencies addObject:[[MyClass alloc] initWithAbbr:abbr]]; } MyPicker *picker = [[MyPicker alloc] initWithData:[NSArray arrayWithArray:currencies]]; </code></pre> <p>MyPicker.h:</p> <pre><code>@property (nonatomic, retain) NSArray *currencies; </code></pre> <p>MyPicker.m:</p> <pre><code>- (id)initWithData:(NSArray *)data { self = [super init]; if (self) { self.currencies = data; self.datasource = self; self.delegate = self; } return self; } #pragma mark - UIPickerViewDataSource - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { return 1; } - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{ return self.currencies.count; } - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{ // sometimes crashes MyClass *currency = self.currencies[row]; return [currency showString]; } #pragma mark - UIPickerViewDelegate - (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{ [self notifySelection]; } - (void)notifySelection { NSInteger index = [self selectedRowInComponent:0]; // here may crash because of index out of bound MyClass *currency = self.currencies[index]; // send the selected currency to view controller } </code></pre>
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    1. COWhere did you read that notifyTarget: was an acceptable method to use? I've **never** seen it used, and objc_msgSend is a clear indication that you're doing something wrong.
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    2. COActually it was modified from https://github.com/TimCinel/ActionSheetPicker . It's an actionsheet with pickerview, and the notifyTarget method is called when the "done" button is pressed so that the origin view controller knows which option is selected.
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    3. COThat project has 54 issues 20 pull requests and hasn't been updated for over two years. I wouldn't be using it. If notify target is failing, just use UIPickerView and it's delegate in a more standard way.
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