Attributes.md

Attributes

final

cannot subclass. compiler will optimise.

class

can subclass

static

Static

dynamic

Dynamic declaration tells the compiler that dynamic dispatch should be used to access that member.

By prefixing a declaration with the dynamic keyword, the declaration is implicitly marked with the @objc attribute.

class Test {
  dynamic var name: String
}

@objc

The objc attribute makes the declaration available in Objective-C, which is a requirement for it to be dispatched by the Objective-C runtime.

class Test {
  @objc func callMe() {}
}

some

The some attributes is used to return back Opaque types. This solves the Self-requirement problem in Protocols.

protocol Fruit { }

func giveFruits() -> [Fruit] { ... }

///extension Fruit: Equatable <<--- compilation error. Fruit can only be used as a generic constraint because it has Self or associated type requirements.

U cant compare things conforming to Fruit, because you dont know what their types (hidden behind the protocol-wrapper) are. The protocol is "non-opaque".

struct Apple: Fruit { ... }
extension Int: Fruit { }

//would not make sense to compare two things conforming to Fruit protocol

But using attribute some will return opaque types which solve this problem, because even though we just see a protocol being used, internally the Swift compiler knows exactly what that protocol actually resolves to.

func giveFruits() -> some [Fruit] { ... }

An important note here is that functions with opaque return types must always return one specific type.

inline

bla bla bla