Use NSSortDescriptor. Just search the documentation on it and there some very simple examples you can copy right over. Here is a simplified example:
NSSortDescriptor *valueDescriptor = [[NSSortDescriptor alloc] initWithKey:@"MyStringVariableName" ascending:YES];
NSArray *descriptors = [NSArray arrayWithObject:valueDescriptor];
NSArray *sortedArray = [myArray sortedArrayUsingDescriptors:descriptors];
And just like that you have a sorted array.