Question

I would like to read in an Array I have stored in a PLIST, modify an element, and store it back to the PLIST.

My simple code is as follows:

NSArray *mathScoreArray;
NSNumber *score1 = [NSNumber numberWithInteger:score];
NSMutableArray *scoreArray1 = [[NSArray arrayWithArray:mathScoreArray] init];
[scoreArray1 replaceObjectAtIndex:4 withObject:score1];
[dictionary setObject:scoreArray1 forKey :@"mathScoreArray"];
[dictionary writeToFile:finalPath atomically:YES];

I’m getting errors for the ‘replaceObjectAtIndex’ for modifying the array.
How can I do this??

Just for reference, my plist looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>mathQues</key>
    <integer>1</integer>
    <key>mathScore</key>
    <integer>0</integer>
    <key>mathScoreArray</key>
    <array>
        <integer>10</integer>
        <integer>20</integer>
        <integer>30</integer>
        <integer>40</integer>
        <integer>50</integer>
    </array>
</dict>
</plist>

Extending the problem, eventually I would like to shift the array one place to right and store a new incoming value on top [just like a stack].

Thanks for pointers.
user

Answer 1

Change this line:

    NSMutableArray *scoreArray1 = [[NSArray arrayWithArray:mathScoreArray] init];
// you need NSMutableArray, not NSArray ^
//                           you already got an array, no need to initialize ^

to:

    NSMutableArray *scoreArray1 = [NSMutableArray arrayWithArray:mathScoreArray];

Also, in your code there is no sign of how did you read the NSArray to begin with.