Question

I have a line of code that will work differently depending on the datatypes “day” and “1”. I believe it is the following although I will check my source code later.

day = day + 1;

Does this make sense? What would the differences be?

Answer 1

NSInteger is a type definition that describes an integer – but it is NOT equivalent to int on 64-bit platforms.
You can examine the typedef by cmd-clicking on NSInteger in Xcode.
NSInteger is defined as int when building a 32-bit app and as long for 64-bit apps.
Most of the time you can replace int with NSInteger, but there are some things to consider when doing so.
Apple’s 64-Bit Transition Guide for Cocoa has some information about that.

NSNumber is a class that helps you to store numeric types as object. It has methods to convert between different types and methods to retrieve a string representation of your numeric value.
If you use a variable day of type NSNumber* the way you did in your example, you are not modifying the value of day but its memory address.

If you are working with time values you also could take a look at NSDate.