[swift-users] lazy initialisation

[Mark Dalrymple]

Here's the one I started with:

   lazy var c:Int = {return a*b}()

and ended up with:

    lazy var c:Int = {return self.a * self.b}()

It's in a closure, so need to explicitly reference self.

Cheers,
++md



On Mon, Jul 4, 2016 at 3:04 PM, J.E. Schotsman via swift-users <
swift-users at swift.org> wrote:

>
> > On 04 Jul 2016, at 19:21, Zhao Xin <owenzx at gmail.com> wrote:
> >
> > You'd better sharing some of you code here first.
>
> For example, consider this:
>
> class TestStruct1
>         {
>         let a = 10
>         let b = 20
>         let c:Int = {return self.a*self.b}()
>         }
>
> Of course this is a trivial example. In reality the calculation of c from
> a and b might take longer.
>
> Since this is not allowed I try
>
> struct TestStruct2
>         {
>         let a = 10
>         let b = 20
>         lazy var c:Int = {return a*b}()
>         }
>
> Not allowed either even though neither a nor b is lazy.
> I have to do
>
> struct TestStruct3
>         {
>         let a = 10
>         let b = 20
>
>         private var cInitialized = false
>         private var _c = 0
>         var c:Int
>          {
>          mutating get {
>         if !cInitialized
>                 {
>                 _c = a*b
>                 cInitialized = true
>                 }
>          return _c }
>          }
>         }
>
> BTW I pasted Mark’s code in a playground and it compiles indeed.
> What’s the difference?
>
> Jan E.
>
>
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