Question

I have an nsmutablearray named nsmarrMedicineInfo. I want to sort the element by using NSSortDescriptor. When I execute the following code it shows NSUnknownKeyException. I can not find what will be the key of the array.

NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"sort" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)] autorelease];
NSArray *sort = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray = [nsmarrMedicineInfo sortedArrayUsingDescriptors:sort];

Answer 1

Here key will be one of the property(key-value pair) of your custom object of array nsmarrMedicineInfo, on which you wish to sort your array.
As in apple’s doc:

An instance of NSSortDescriptor describes a basis for ordering objects
by specifying the property to use to compare the objects, the method
to use to compare the properties, and whether the comparison should be
ascending or descending.

But if nsmarrMedicinInfo object consists of strings only then you can use sortedArrayUsingSelector method instead of sortDescriptor.

Thanks,