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PONSJSONSerialization - modify an object into a json file
 

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  1. PONSJSONSerialization - modify an object into a json file
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    <p>I have this simple json file in my iphone/ipad project. </p> <pre><code>{"initial_page" : Page_Selected} </code></pre> <p><code>Page_Selected</code> is an <code>NSInteger</code></p> <p>I want to modify through a <code>UIPickerView</code> the value of the <code>"initial_page"</code>. How to do that? </p> <p>of course I've already done the <code>UiPickerWiew</code> selection part and about the json modification, I will write it into the </p> <p><code>-(void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponents:(NSInteger)component{ }</code> </p> <p>function.</p> <p>Maybe function that does the job is <code>[[jsonParsed setInteger:row forKey:@"initial_page"]</code> but this way, the debugger returns me "unrecognized selector sent" exception.</p> <p>I need only the part in which to modify the <code>json</code> parameter with <code>"initial_page"</code> as the key. </p> <p>anyone can help me?</p> <hr> <p>that's what I got.</p> <pre><code>NSError *jsonParsingError = nil; NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Config" ofType:@"json"]; NSMutableDictionary *configJson = [NSJSONSerialization JSONObjectWithData:[NSData dataWithContentsOfFile:filePath] options:NSJSONReadingMutableContainers error:&amp;jsonParsingError]; [configJson setValue:[NSNumber numberWithInt:row] forKey:@"initial_page"]; NSLog(@"%@",jsonParsingError); </code></pre> <p>the last line returns me <code>(null)</code>, so the json file is ok.</p> <p>BUT, If I print out <code>[configJson objectForKey:@"inital_page"]</code> then I can see it changes... so, is there a kind of "commit" or "save" command in order to make it persistent?</p> <hr> <p>following suggestions:</p> <pre><code>NSData * modified = [NSJSONSerialization dataWithJSONObject:configJson options:NSJSONWritingPrettyPrinted error:&amp;jsonParsingError]; [modified writeToFile:filePath options:NSDataWritingAtomic error:&amp;jsonParsingError]; NSLog(@"returned error: %@", [jsonParsingError localizedDescription]); </code></pre> <p>again, last line returns me <code>(null)</code> but I can't find any modification in the file</p> <hr> <p>after changes, I can save the modification of the <code>initial_page</code>, but this works only on <code>iPhone/iPad Simulator</code> and not on the real device debugging.</p> <p>here's what I do:</p> <pre><code>if([modified wirteToFile:filePath options:NSDataWritingFileProtectionNone error:&amp;jsonParsingError]) NSLog(@"writing ok") else NSLog(@"not ok with error :%@",jsonParsinError); </code></pre> <p><code>Iphone simulator</code> has no problem with the last 4 lines, but when I run it on physical <code>iPhone</code>, the last <code>NSLog</code> gives:</p> <pre><code>"not ok with error : Error Domain=NSCocoaErrorDomain Code=513 The Operation Could not be completed. Operation not permitted" </code></pre> <p>it seems a permission denied in writing the json file.</p>
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