Protocol Composition in Swift and Objective-C
Any protocol in Swift that contains optional members must be marked as
@objc. I have written before about avoiding@objcin your Swift code as much as possible. When@objcinfiltrates your object graph, nearly everything must inherit fromNSObjectwhich means you cannot use Swift structs, enums, or other nice features. This leaves you not writing Swift, but merely “Objective-C with a new syntax”.[…]
A better approach is to split up large protocols into smaller ones, and provide a unique property (like a delegate) for each one.
[…]
This design transfers the “optional-ness” from the protocol itself to an additional optional property on the class. If you want headers and footers in your table view, you can opt-in to those by setting
titlesDataSource. To opt-out, you can set this property tonil. The same applies toreorderingDataSource, and so on.[…]
Instead of numerous disjoint protocols, you can design a union of protocols. This provides a single, top-level “entry point” to reference. You can extract the optional members of a protocol into a new protocol, then add an optional property for this new protocol on the original protocol. The result is a comprehensive top-level protocol and a set of “nested” protocols.
1 Comment RSS · Twitter
So basically, the language lacks a useful semantic feature, so lets restructure out entire design philosophy but try to make it still sounds like its good engineering…?
