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3

1

Given a function with a generic parameter, I would like to pass a value of which type is Any.Type to the function but it doesn't compile.

func foo<T>(_ type: T.Type) 
 print(type)


foo(Any.self) // ok
foo(Int.self) // ok

let a: Any.Type = Any.self // ok
let b: Any.Type = Int.self // ok

foo(a) // error: expected an argument list of type '(T.Type)'
foo(b) // error: expected an argument list of type '(T.Type)'

My assumption is that:

1. foo(Any.self) successfully compiles and the type placeholder T would hold Any.




2. Similarly, if a value of type Any.Type is given, the T should be resolved into Any

Could you explain why this code doesn't work?

swift generics metatype

share|improve this question

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  
  See Why can't I pass a Protocol.Type to a generic T.Type parameter? – for foo(Any.self), Any.self is treated as Any.Protocol allowing the code to compile.
  
  – Hamish
  Mar 25 at 13:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Hamish Thank you for the link! It really helped me understand how it works.
  
  – Yonguk Jeong
  Mar 26 at 10:26
  

  
  
  
  

add a comment | 

3

1

Given a function with a generic parameter, I would like to pass a value of which type is Any.Type to the function but it doesn't compile.

func foo<T>(_ type: T.Type) 
 print(type)


foo(Any.self) // ok
foo(Int.self) // ok

let a: Any.Type = Any.self // ok
let b: Any.Type = Int.self // ok

foo(a) // error: expected an argument list of type '(T.Type)'
foo(b) // error: expected an argument list of type '(T.Type)'

My assumption is that:

1. foo(Any.self) successfully compiles and the type placeholder T would hold Any.




2. Similarly, if a value of type Any.Type is given, the T should be resolved into Any

Could you explain why this code doesn't work?

swift generics metatype

share|improve this question

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  
  See Why can't I pass a Protocol.Type to a generic T.Type parameter? – for foo(Any.self), Any.self is treated as Any.Protocol allowing the code to compile.
  
  – Hamish
  Mar 25 at 13:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Hamish Thank you for the link! It really helped me understand how it works.
  
  – Yonguk Jeong
  Mar 26 at 10:26
  

  
  
  
  

add a comment | 

Given a function with a generic parameter, I would like to pass a value of which type is Any.Type to the function but it doesn't compile.

func foo<T>(_ type: T.Type) 
 print(type)


foo(Any.self) // ok
foo(Int.self) // ok

let a: Any.Type = Any.self // ok
let b: Any.Type = Int.self // ok

foo(a) // error: expected an argument list of type '(T.Type)'
foo(b) // error: expected an argument list of type '(T.Type)'

My assumption is that:

1. foo(Any.self) successfully compiles and the type placeholder T would hold Any.




2. Similarly, if a value of type Any.Type is given, the T should be resolved into Any

Could you explain why this code doesn't work?

swift generics metatype

share|improve this question

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

func foo<T>(_ type: T.Type) 
 print(type)


foo(Any.self) // ok
foo(Int.self) // ok

let a: Any.Type = Any.self // ok
let b: Any.Type = Int.self // ok

foo(a) // error: expected an argument list of type '(T.Type)'
foo(b) // error: expected an argument list of type '(T.Type)'

share|improve this question

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

share|improve this question

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges

asked Mar 25 at 13:20

Yonguk JeongYonguk Jeong

18455 bronze badges