[swift-users] How to call a private protocol extension method from a public protocol extension method

[Kevin Greene]

Oh gotcha. I totally misunderstood the question. Sorry about that!
I didn't actually realize you can extend protocols. Cool stuff! For anybody
else who is uninitiated:
https://www.raywenderlich.com/109156/introducing-protocol-oriented-programming-in-swift-2

On Wed, Jun 22, 2016 at 3:17 PM, David Ungar <ungar at mac.com> wrote:

> Kevin,
>
> Thank you so much for helping me out. I wasn’t clear, but I’m hoping to
> find a solution that uses only value types and protocols.
>
> - David
>
>
> On Jun 22, 2016, at 1:19 PM, Kevin Greene <kgreenek at gmail.com> wrote:
>
> You could have your common superclass implement your protocol. E.g...
>
> public protocol PublicProto {
>   func publicFn()
> }
>
> public class CommonSuper: PublicProto {
>   public func publicFn() { specificPrivate() }
>   private func specificPrivate() {}
> }
>
> private class SubA: CommonSuper {
>   override private func specificPrivate() { /* ... */ }
> }
>
> private class SubB: CommonSuper {
>   override  private func specificPrivate() { /* ... */ }
> }
>
> I don't know what you're doing specifically, but I would guess that a
> cleaner approach would likely be to get rid of the super class entirely,
> and pull the shared logic from your two subclasses into a separate object
> that both classes instantiate, or have injected. Then have your two classes
> implement PublicProto directly. That discussion would probably be best had
> on another mailing list though.
>
> On Wed, Jun 22, 2016 at 11:19 AM, David Ungar via swift-users <
> swift-users at swift.org> wrote:
>
>> I love protocol-oriented programming because of the guarantees that come
>> with value types. But I cannot figure out how to do the same factoring I
>> can do with the class side of the the language. I want to factor out common
>> code into a public method that calls specific code in a private method & I
>> want to do this for value types.
>>
>> Here it is in classes:
>>
>> public class CommonSuper {
>>   public func publicFn() { … specificPrivateFn()  … }
>>   private func specificPrivateFn() { }
>> }
>>
>> private class SubA {
>>   override private func specificPrivate() { … }
>> }
>> private class SubB {
>>   override  private func specificPrivate() { … }
>> }
>>
>> I have tried it lots of ways with protocols, and can get none to compile.
>> Here is one:
>>
>> public protocol PublicProto {
>>     func publicFn()
>> }
>>
>> private protocol PrivateProto {
>>     func specificPrivateFn()
>> }
>>
>> public extension  PublicProto where Self: PrivateProto { // Error:
>> Extension cannot be declared public because its generic requirement uses a
>> private type
>>     public func publicFn() { specificPrivateFn() } // Error: Cannot
>> declare a public instance method in an extension with private requirements
>> }
>>
>> private struct SA: PublicProto, PrivateProto {
>>     private func specificPrivateFn() {}
>> }
>> private struct SB: PublicProto, PrivateProto {
>>     private func specificPrivateFn() {}
>> }
>>
>> What am I doing wrong?
>>
>> Thanks,
>>
>> - David
>>
>> _______________________________________________
>> swift-users mailing list
>> swift-users at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
>>
>>
>
>
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