[swift-users] Foundation on Linux `CFBooleanGetTypeID`/`CFGetTypeID`

Tony Parker anthony.parker at apple.com
Tue May 24 15:19:37 CDT 2016

> On May 24, 2016, at 1:11 PM, Ryan Lovelett <swift-dev at ryan.lovelett.me> wrote:
> On Tue, May 24, 2016, at 04:07 PM, Tony Parker wrote:
>> Let’s get a bug into JIRA, then we’ll figure out what we should do here.
> That's the problem for me. What is the bug? Based on the code example I provided in this thread. I'm somewhat convinced that the bug is that Foundation on Linux/Glibc is "broken". In that it does not match the behavior of Foundation on Darwin, yet it has the desired behavior.

What I mean is that I want to track the issue in JIRA so we don’t lose it, and so we can find it later when looking for issues that prevent fully cross-platform behavior. We can look into fixing these in several ways, including adding new API in both frameworks, changing implementations, etc.

- Tony

>> - Tony
>>> On May 24, 2016, at 1:03 PM, Jens Alfke <jens at mooseyard.com <mailto:jens at mooseyard.com>> wrote:
>>>> On May 24, 2016, at 12:52 PM, Tony Parker <anthony.parker at apple.com <mailto:anthony.parker at apple.com>> wrote:
>>>> One other possibility is using the objCType property on NSNumber’s superclass NSValue to check.
>>> That doesn’t work, unfortunately, at least not with Apple’s Foundation. NSNumbers initialized with booleans have objcType “c” because `BOOL` is just a typedef for `char`. So the only way to tell a boolean apart from an 8-bit int is to compare the object pointer against the singleton true and false objects.
>>> Here’s a snippet of Obj-C code I use for this in my JSON encoder:
>>>     char ctype = self.objCType[0];
>>> switch (ctype) {
>>> case 'c': {
>>> // The only way to tell whether an NSNumber with 'char' type is a boolean is to
>>> // compare it against the singleton kCFBoolean objects:
>>> if (self == (id)kCFBooleanTrue)
>>> return yajl_gen_bool(gen, true);
>>> else if (self == (id)kCFBooleanFalse)
>>> return yajl_gen_bool(gen, false);
>>> else
>>> return yajl_gen_integer(gen, self.longLongValue);
>>>         }
>>>> I haven’t seen how much of this is implemented in corelibs-foundation yet. 
>>> I took a peek at the Swift NSNumber and NSValue implementations on Github, and the objcType stuff doesn’t seem to be functional. It looks like objcType will only have a value if the object was initialized as an NSValue with the type code passed in, not if the typical NSNumber initializers were used.
>>> —Jens

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