Question

I have this simple json file in my iphone/ipad project.

{"initial_page" : Page_Selected}

Page_Selected is an NSInteger

I want to modify through a UIPickerView the value of the "initial_page". How to do that?

of course I’ve already done the UiPickerWiew selection part and about the json modification, I will write it into the

-(void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponents:(NSInteger)component{ }

function.

Maybe function that does the job is [[jsonParsed setInteger:row forKey:@"initial_page"] but this way, the debugger returns me “unrecognized selector sent” exception.

I need only the part in which to modify the json parameter with "initial_page" as the key.

anyone can help me?

---

that’s what I got.

NSError *jsonParsingError = nil;
NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Config" ofType:@"json"];
NSMutableDictionary *configJson = [NSJSONSerialization
                JSONObjectWithData:[NSData dataWithContentsOfFile:filePath]
                options:NSJSONReadingMutableContainers error:&jsonParsingError];

[configJson setValue:[NSNumber numberWithInt:row] forKey:@"initial_page"];

NSLog(@"%@",jsonParsingError);

the last line returns me (null), so the json file is ok.

BUT, If I print out [configJson objectForKey:@"inital_page"] then I can see it changes… so, is there a kind of “commit” or “save” command in order to make it persistent?

---

following suggestions:

NSData * modified = [NSJSONSerialization dataWithJSONObject:configJson options:NSJSONWritingPrettyPrinted error:&jsonParsingError];

[modified writeToFile:filePath options:NSDataWritingAtomic error:&jsonParsingError];
NSLog(@"returned error: %@", [jsonParsingError localizedDescription]);

again, last line returns me (null) but I can’t find any modification in the file

---

after changes, I can save the modification of the initial_page, but this works only on iPhone/iPad Simulator and not on the real device debugging.

here’s what I do:

if([modified wirteToFile:filePath options:NSDataWritingFileProtectionNone error:&jsonParsingError])
   NSLog(@"writing ok")
else
   NSLog(@"not ok with error :%@",jsonParsinError);

Iphone simulator has no problem with the last 4 lines, but when I run it on physical iPhone, the last NSLog gives:

"not ok with error : Error Domain=NSCocoaErrorDomain Code=513 The Operation Could not be completed. Operation not permitted"

it seems a permission denied in writing the json file.

Answer 1

the problem is solved: the main wrong concept is to write and / or modify files in the main bundle. now I do this in the NSDocumentDirectory

this way, I get no error and I can read/write the data directly in/from the iPhone.

I followed this guide: link of course I use json as filter instead pdf.