> On Apr 14, 2016, at 10:45 AM, soyer via swift-users <swift-users@swift.org>
> wrote:
>
> Do you know why is the init?(length length: Int) NSMutableData's initializer
> failable?
Because the Objective-C declaration in <Foundation/NSData.h> declares the
return type as ‘nullable’:
- (nullable instancetype)initWithLength:(NSUInteger)length;
> The memory allocation can fail, but I think Swift doesn't handle that cases.
> (it is not a real issue in a modern OS)
Not on a modern 64-bit desktop OS, but it can be an issue on some other
platforms. In a 32-bit process (still supported on iOS and Mac OS) malloc can
fail if the process's address space is fragmented enough that there are no free
blocks large enough for the allocation. On an OS without a VM pager, like many
embedded systems, malloc can fail if physical RAM is exhausted.
(I’m actually not sure if this is the reason why that initializer is failable.
It’s possible this is a mistake, or Apple’s frameworks team had some other
architectural reason for allowing it to fail. Historically, the design pattern
for initializers in Objective-C always allows them to return nil.)
> The code on github calls a non failable initializer.
That’s for the native-Swift Foundation framework coming in Swift 3. I’d guess
they’ve adopted the same method signature as in Apple’s Foundation, for
compatibility.
—Jens
_______________________________________________
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
