[swift-evolution] Initializers
John McCall
rjmccall at apple.com
Tue Jan 31 13:51:23 CST 2017
> 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.
What problem are you trying to solve here? Are you annoyed at having to write super.init() and/or initialize your instance variables instead of having the compiler "do the right thing" automatically, or are you worried that calling super.init() will be a small but unnecessary expense at runtime? Because these seem like completely different problems that should be addressed in completely different ways.
John.
>
>
> 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
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
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