Collection element of type 'CGSize' is not an Objective-C object

I'm trying a give a NSDictionary key value a CGSize, and XCode is giving me this error. My code:

       NSArray *rows = @[
        @{@"size" : (CGSize){self.view.bounds.size.width, 100}
          }
        ];

Why am I getting an error here? If its impossible to store a CGSize in a dict, then what's an alternative approach?

EDIT: now getting "Used type 'CGSize' (aka 'struct CGSize') where arithmetic, pointer, or vector type is required" error with this code:

NSDictionary *row = rows[@0];
CGSize rowSize = [row[@"size"] CGSizeValue] ? : (CGSize){self.view.bounds.size.width, 80};