Re: Determining underlying type of array in swift?
Re: Determining underlying type of array in swift?
- Subject: Re: Determining underlying type of array in swift?
- From: Rick Mann <email@hidden>
- Date: Wed, 09 Dec 2015 15:08:00 -0800
> On Dec 9, 2015, at 14:57 , Quincey Morris <email@hidden> wrote:
>
> On Dec 9, 2015, at 14:35 , Rick Mann <email@hidden> wrote:
>>
>> If I have var foo : [Int], how can I get that type, Int? I need to get the size of each element.
>
> I imagine there’s a direct way, but I can’t find it in a program. You can do something like this:
>
> strideofValue (foo [0]) // but this requires foo.count != 0, or:
> strideof (foo [0].dynamicType) // which seems to work in a playground even for empty arrays
>
> Note that I’m not sure there’s an API guarantee that the Array<> elements are stored contiguously in memory. If you want that, you should probably use ContiguousArray<> instead. (That also gives you API to directly/unsafely access the memory too, IIRTGHF** correctly.)
>
> Do be careful, though. If you’re accessing Ints raw-ly, and (say) saving them or transmitting them to another application or platform, you might also have to worry about element size and endianness differences, theoretically.
Actually, looking further, what I have is an UnsafePointer<Int32>. This is actually coming from Objective-C++ code (it's how I bridge my Swift code to our extensive C++ codebase). The class has a property:
@property (nonatomic, readonly, nullable) const int* faceIndexes;
Which shows up in swift as UnsafePointer<Int32>, and I can treat it as an array:
myObjCObj.faceIndexes[0]
So, really, I need to get at the UnsafePointer's type. Is that:
var up: UnsafePointer<Int32>
sizeof(up.memory.dynamicType)
That seems to work. Wordy, but gets the job done.
>
> ** "If I Read The Generated Header File"
--
Rick Mann
email@hidden
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