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swift 註解 (和java比照)@attribute name

Attributes provide more information about a declaration or type. There are two kinds of attributes in Swift, those that apply to declarations and those that apply to types.

You specify an attribute by writing the @ symbol followed by the attribute’s name and any arguments that the attribute accepts:

  1. @attribute name
  2. @attribute name(attribute arguments)

Some declaration attributes accept arguments that specify more information about the attribute and how it applies to a particular declaration. These attribute arguments are enclosed in parentheses, and their format is defined by the attribute they belong to.

 

  1. @dynamicMemberLookup
  2. struct DynamicStruct {
  3. let dictionary = ["someDynamicMember": 325,
  4. "someOtherMember": 787]
  5. subscript(dynamicMember member: String) -> Int {
  6. return dictionary[member] ?? 1054
  7. }
  8. }
  9. let s = DynamicStruct()
  10. // Using dynamic member lookup
  11. let dynamic = s.someDynamicMember
  12. print(dynamic)
  13. // Prints "325"
  14. // Calling the underlying subscript directly
  15. let equivalent = s[dynamicMember: "someDynamicMember"]
  16. print(dynamic == equivalent)

 

https://docs.swift.org/swift-book/ReferenceManual/Attributes.html#grammar_attribute-argument-clause