如何对已知对象的NSArray进行排序，以确保FIRST记录等于已知对象？

Question

If I have an object and setup such as:

MyObject *objectOne = ....;

NSArray *arrayOfMyObjects = [self.someObject valueForKey=@"myObjects"] allObjects];

where valueForKey=@"objects" is an NSMutableSet of MyObject types,

How exactly do I use sorting to ENSURE (or at least attempt to ensure) that objectOne is equal to
[arrayOfMyObjects objectAtIndex:0] ?

Basically ensuring that the first object of the NSArray is equal to a known object I have? This is for the purposes of a UITableView and making sure the top most record is objectOne when it is loaded?

I'm guessing there's some sort descriptors trickery required but not quite sure the syntax?

Thanks!

Answer 1

You could use a comparator block to ensure that it is first:

MyObject *objectOne;
NSArray *array = [[self.someObject valueForKey:@"myObjects"] allObjects];
NSArray *sortedArray = [array sortedArrayUsingComparator:^(id obj1, id obj2) {
    if(obj1 == objectOne) return (NSComparisonResult)NSOrderedAscending;
    if(obj2 == objectOne) return (NSComparisonResult)NSOrderedDescending;
    return (NSComparisonResult)NSOrderedSame;
}];

The typecast on the returns is to remove the compiler warning for incorrect argument types. NSOrdered... are of type enum _NSComparisonResult , and the method expects a NSComparator, which is defined as NSComparisonResult ^(id obj1, id obj2) , but NSComparisonResult and enum _NSComparisonResult are not the same.