[swift-evolution] Initializers

[Robert Widmann]

This seems to contradict Swift’s goal of being safe by default <https://swift.org/about/>, no?  It would make me incredibly uncomfortable if there were a backdoor in DI, even if that backdoor emitted traps when it fails.

> On Jan 28, 2017, at 1:07 PM, Victor Petrescu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Hello,
> 
> My name is Victor, been a developer (C, delphi, php, java, js) for the last 10 years or so and lately I had the chance to try swift. I have a suggestion/question regarding initializers.
> 
> Sidenote: If this is not the correct mailing list for this can you please redirect me to the right place?
> 
> Consider the following 2 classes and code:
> 
> class A {
>      var x:Int
> 
>      init() {
>          x = 1
>      }
> }
> 
> class B : A {
>     override init() {
>          super.init() // Swift FORCES this call
>          x = 2
>     }
> }
> 
> var a:B
> for i in 0...99999999 {
>     a = B()  // Whatever... some code that inits B.
> }
> 
> This results in 99999999 x = 1 then 99999999 x = 2... the x = 1 being totally useless in this particular case.
> 
> In this case, if you don't make the super init you get a compile error.
> 
> Now... I see the use of this. It ensure that all members are initialized. For example if A had a private variable (another strange choice here with what private means in swift but I haven't thought on it yet so... maybe is a cool choice), the B init could not initialize it. I also understand that the cases when you need this minor performance gain are rather rare (but they do still exist). So I guess the choice for the super.init() had that reasoning.
> 
> Still... my suggestion would be to give a warning, maybe force a key word before the init (like iKnowWhatImDoing init() {}), THEN in case vars are still not inited give a runtime error (afaik Objective C for example gives a warning). That ensures everything is ok and also allows programmers that have strange cases to treat them accordingly.
> 
> Anyway... that would be my suggestion. Maybe this was discussed before also... If this was discussed before can you please point me to the discussion? I like to understand the choices for the tools I use.
> 
> 
> P.S. Please excuse any grammatical errors... English is not my first language.
> 
> Thank you for your time and have a great day,
> Petrescu Victor
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