Maybe it's an existing project, or for some other reason you are still using Objective-C, here's a nugget for you:

__auto_type i = @123;
NSLog(@"class: %@", NSStringFromClass([i class]));

const __auto_type j = @123;
j = @1;

That last line will compile with an error:

Cannot assign to variable 'j' with const-qualified type 'NSNumber *__strong const'

Typing _auto_type and const __auto_type looks a little unwieldy, so we can define a few macros:

#define let const __auto_type
#define var __auto_type

and use them instead:

var i = @123;
NSLog(@"class: %@", NSStringFromClass([i class]));

let j = @123;
j = @1; //Compilation error

(Probably more useful to store the macros in a new header file and #import them)

I picked up this tip from @_nb

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