[swift-evolution] Overriding computed properties with let constants?

[David Sweeris]

I’m not sure if I like it, but declaring it as a let could disallow subclasses from overriding it, just like any other let.

- Dave Sweeris

> On Apr 23, 2016, at 2:30 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I already see the problem here:
> 
> class A { var x: Int { return 42 } }
> class B: A { override let x = 7 } // assume that will work
> class C: B { override var x: Int { /* wait this wont work anymore */ } }
> 
> You won’t be able to override an immutable constant.
> 
> I don’t like such a change.
> 
> -- 
> Adrian Zubarev
> Sent with Airmail
> 
> Am 23. April 2016 bei 21:19:27, Roman Zhikharevich via swift-evolution (swift-evolution at swift.org <mailto:swift-evolution at swift.org>) schrieb:
> 
>> I think, it could be a good idea to make computed properties overridable with let constants.
>> 
>> Something like this:
>> 
>> class Parent {
>>     var x: Int {
>>         let x = 42
>>         /*
>>          * Compute x...
>>          */
>>         return x
>>     }
>> }
>> 
>> class Child: Parent {
>>     /*
>>      * Sometimes you need to override computed properties with simple constants.
>>      * This is currently done like this.
>>      */
>>     //override var x: Int {return 7}
>>     
>>     /*
>>      * But this looks neater.
>>      * Currently this gives "error: cannot override with a stored property 'x'".
>>      */
>>     override let x = 7
>> }
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