[swift-evolution] abstract keyWord proposal

[David Scrève]

	Hi Everyone,

	Nice to see this new swift-evolution process….I’m not sure to completely understand the whole process of requesting evolutions, but I’m trying
to do…

	As I develop sort of framework, I usually have classes that I wanted to partially in the framework and force the user to implement others parts.

	For example, I have a WebService class that manage the whole process to perform asynchronous call, error management.
	This class has an abstract property that is specific for each WebService call.

	Then I would like to make the URL property abstract and, consequently, the whole WebService class abstract : The WebService cannot be directly instantiated.

	The goal of this feature would be to extend to method.
	This behavior already exists in Java and is really useful. 

	The workaround is to make an URL property that returns invalid value or make assertion, but the error is only detected at runtime.

	My proposal would be to just add a keyword before func, class or var. An abstract property or func should not provide implementation.	

	Regards,


David


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