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I want to do something like this:
class SomeClass<Element> { }
extension SomeClass: SomeProtocol where Element: String { }
It tells me:
Extension of type "SomeClass" with constraints cannot have an inheritance clause.
I could have sworn up to this point that this was one of the bread and butter features of the protocol/extension/generic/associatedtype paradigm. Is there another way to implement this?
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Conditional conformances were introduced in Swift 4.1, and refined in Swift 4.2 to allow you to query them at runtime. They allow types to conform to a protocol only when certain conditions are met – hence “conditional conformance”. For example, if we had a Purchaseable protocol: protocol Purchaseable { func buy() }
In Swift, you can even extend a protocol to provide implementations of its requirements or add additional functionality that conforming types can take advantage of. For more details, see Protocol Extensions. Note. Extensions can add new functionality to a type, but they can't override existing functionality.
Protocols provide a blueprint for Methods, properties and other requirements functionality. It is just described as a methods or properties skeleton instead of implementation. Methods and properties implementation can further be done by defining classes, functions and enumerations.
This was implemented in Swift 4.1.
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