problem writing a NSMutableArray to file in cocoa

cocoa nsmutablearray writefile
Luuk picture Luuk · Apr 15, 2009 · Viewed 8.1k times · Source

A real beginners question. I have a NSView subclass in which I create a NSMutableArray containing NSValues. When I want to write the array to a file using writetofile:atomatically: the file is created but it contains none of the NSValues that the mutable array does contain. Does anyone know how I successfully can write this mutable array to a file?

Thanks

Answer

Jesse Rusak picture Jesse Rusak · Apr 15, 2009

NSValues can't be saved in a plist (which is what writeToFile:atomically: does). Take a look here for the values you can save. (NSNumber is a kind of NSValue you can save, but other NSValues will fail.)

If you want to save your array with NSValues, you can use archiving instead of writeToFile:atomically:. NSArray and NSValue both support archiving, so you just convert the array to an archive and save that data to a file. (It will include the NSValues as well.) The code looks something like this:

[NSKeyedArchiver archiveRootObject:myArray toFile:@"myPath"];

To load it, just use:

NSArray *myArray = [NSKeyedUnarchiver unarchiveObjectWithFile:@"myPath"];

Related questions

How do I convert NSMutableArray to NSArray?

How do I convert NSMutableArray to NSArray in objective-c?

Read More
How do copy and mutableCopy apply to NSArray and NSMutableArray?

What is the difference between copy and mutableCopy when used on either an NSArray or an NSMutableArray? This is my understanding; is it correct? // ** NSArray ** NSArray *myArray_imu = [NSArray arrayWithObjects:@"abc", @"def", nil]; // No copy, increments retain count, result is …

Read More
How to sort NSMutableArray using sortedArrayUsingDescriptors?

I have a question about sorting NSMutableArray. I can use sortedArrayUsingDescriptors: method to sort an array with objects. For example I have an NSMutableArray of places where I have an attribute frequency (int value) and I want to sort descending …

Read More