So, adding lazy lets it work with the closure (makes self available to the
closure):
lazy var backgroundSession : NSURLSession =
{
let config =
NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("com.matterport.StandaloneShowcase.ModelFetchConfiguration")
let session = NSURLSession(configuration: config, delegate: self,
delegateQueue: nil)
return session
}()
Without lazy, you cannot initialize it with a call to a member (e.g. =
self.createbackgroundSession()). You also cannot initialize it in init(),
because of the restrictions on initializing and using self. This to me is one
of the more cumbersome areas of the language.
I really wish you could do lazy let foo = .... I don't see why the language
can't support that.
> On Aug 14, 2015, at 17:44 , Quincey Morris
> <[email protected]> wrote:
>
> On Aug 14, 2015, at 17:26 , Jens Alfke <[email protected]> wrote:
>>
>> (Either way, it would still make sense for ‘self’ to be available.)
>
> Yes and no. Because it’s an ivar, the ivar’s value is associated with an
> instance rather than a class, but:
>
> — It’s being initialized by an arbitrary closure. There’s no particular
> reason to regard the closure as associated with any specific instance.
>
> — It’s initializing an ivar. There’s no (accessible) ‘self’ object until all
> of the class’s own ivars are initialized. Similarly, in an initializer, you
> cannot assign ‘self’ to anything, until all ivars are initialized. So even if
> ‘self’ was taken to mean “the” instance, it would still be an error.
>
>
>
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Rick Mann
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