Write to plist file (In Particular row/Item) - ios

Question

I have a .plist file which have this structure,
I want to add or replace the Item 5. I am using this code
NSError *error ;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:#"Introduction.plist"];
NSMutableArray *data = [[NSMutableArray alloc] initWithContentsOfFile:path];
NSString *comment = str;
[data replaceObjectAtIndex:1 withObject:comment];
[data writeToFile:path atomically:YES];
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:path]) {
NSString *bundle = [[NSBundle mainBundle] pathForResource:#"Introduction" ofType:#"plist"];
[fileManager copyItemAtPath:bundle toPath:path error:&error];
}
If I change replaceObjectAtIndex: to 5 it changes my plist structure, and I don't want that.
How can I insert/replace the text at the row 5 (Item 5) of particular Index?

Answer 1

You structure has an array of arrays.
[data replaceObjectAtIndex:1 withObject:comment];
By this code you are replacing an array at index 1 with a string. Do you specifically need to insert to 5th index or do you just need to add it to existing sub array?
NSMutableArray *subArray = [data[sectionIndex] mutableCopy];
if (!subArray) {
subArray = [NSMutableArray array];
}
if (rowIndex<[subArray count]) {
[subArray replaceObjectAtIndex:rowIndex withObject:comment];
}else{
[subArray addObject:comment];
}
[data replaceObjectAtIndex:sectionIndex withObject:subArray];
[data writeToFile:path atomically:NO];
Access the subArray, make it mutable and add or insert at specific index. If you are trying to insert don't forget to include a check if the index is not greater than count of that array.