Write an array on.plist - objective-c

Question

I have a problem. I have this file dictionary .plist:
<plist version="1.0">
<dict>
<key>2</key>
<array>
<string>a</string>
<string>b</string>
<string>c</string>
</array>
</dict>
</plist>
So now I read this file in this way:
NSString* plistPath = [[NSBundle mainBundle] pathForResource:#"dictionary" ofType:#"plist"];
NSMutableDictionary *contentArray = [NSMutableDictionary dictionaryWithContentsOfFile:plistPath];
NSMutableArray *dic = [contentArray objectForKey:#"2"];
NSLog(#"Numero di elementi del dictionary corrispondente a 2: %i", [dic count]);
for (int i = 0; i < [dic count]; ++i) {
NSString *temp = [dic objectAtIndex:i];
NSLog(#"Stringa = %#\n", temp);
}
Now I want to modify the array:
[dic replaceObjectAtIndex:0 withObject:#"ok"];
and I want to write it on the dictionary.plist and I try this:
[contentArray writeToFile:plistPath atomically:YES];
[contentArray release];
But this code doesn't work, and I receive an error, how can I do this?
Thanks

Answer 1

Since you didn't provide the error, I assume the problem might be that
NSMutableDictionary * contentArray = [NSMutableDictionary dictionaryWithContentsOfFile: plistPath];
only creates a mutable container (you can change the content of contentArray, but not the objects (leaves) inside of it.
If you want mutable leaves, use NSPropertyListSerialization instead:
NSMutableDictionary * contentArray = [NSPropertyListSerialization propertyListFromData: [NSData dataWithContentsOfFile: plistPath] mutabilityOption: NSPropertyListMutableContainersAndLeaves format: nil errorDescription: nil];