Trying to create honest NSDecimalNumber in Wax

Question

As I studied the issue I am facing in Trying to create NSDecimal in iPhone-Wax I am now aiming much lower. How can I create a fully functional NSDecimalNumber in Wax?

I have added the following two lines at the top of AppDelegate.lua in a fresh wax project.

local x = NSDecimalNumber:initWithString("2.3")
print(x)
print(x:class())

The output is

(0x631e054 => 0x631d1a0) 2.3
(0x631e924 => 0x25f618) NSCFNumber

instead of something like

(0x621e834 => 0x620c550) <NSDecimalNumber: 0x620c550>

Turning on full logging in wax give the following trace in the debug window:

Creating class for WaxServer(0x621bf40)
Storing reference of class to userdata table WaxServer(0x621bf40 -> 0x621c454)
Storing reference to strong userdata table WaxServer(0x621bf40 -> 0x621c454)
Creating class for NSDecimalNumber(0x261120)
Storing reference of class to userdata table NSDecimalNumber(0x261120 -> 0x6205e44)
Storing reference to strong userdata table NSDecimalNumber(0x261120 -> 0x6205e44)
Creating instance for NSDecimalNumberPlaceholder(0x6213450)
Retaining instance for NSDecimalNumberPlaceholder(0x6213450 -> 0x621d7c4)
Storing reference of instance to userdata table NSDecimalNumberPlaceholder(0x6213450 -> 0x621d7c4)
Storing reference to strong userdata table NSDecimalNumberPlaceholder(0x6213450 -> 0x621d7c4)
Creating instance for NSCFNumber(0x620c550)
Retaining instance for NSCFNumber(0x620c550 -> 0x621e834)
Storing reference of instance to userdata table NSCFNumber(0x620c550 -> 0x621e834)
Storing reference to strong userdata table NSCFNumber(0x620c550 -> 0x621e834)
(0x621e834 => 0x620c550) 2.3
Creating class for AppDelegate(0x621ec50)
:
:

Two things are showing in this log which I did not ask for, NSDecimalNumberPlaceholder and NSCFNumber. I believe these are the source of my grief and I have no idea where they are coming from. Any ideas on how to fix the issue?

Ultimately I want to call the method decimalValue, but wax complains that it can't call a method on a number.

Truelove

would it make a difference if it were a dishonest NSDecimalNumber? ;) – Ima

@Dave DeLong: as long as it can be converted to an NSDecimal. – Truelove

Answer 1

NSDecimalNumber overrides -description to return the number it represents. When you're logging statement is printing "2.3", it is in fact printing the NSDecimalNumber object. You can verify this for yourself by calling -class on your x value and printing that as well.

Lovash

What I'd like to do with the object is to call the decimalValue method. It complains that the number 2.3 does not have that method, so I don't believe it's faking what it's displaying. – Truelove

Sounds like you're getting an NSNumber instead of an NSDecimalNumber back. I wonder if Wax is doing something weird here? – Lovash

An NSNumber should also accepts decimalValue, so this is not an NSNumber. I tried the class method and it says it's and NSCFNumber. – Truelove

@John Smith: Ah hrm. -decimalValue returns a struct. Does Wax even support structs? – Lovash

@Kevin Ballard: yes if you include them in structs.lua – Truelove

@John Smith: OK, because NSCFNumber is the "real" class that most NSNumbers are. It has to do with toll-free bridging. – Lovash

NSNumber and CFNumber are toll free bridged. I have no seen any info on NSCFNumber from Apple. – Truelove

NSCFNumber is an implementation detail. – Lovash