How do I specify that a non-generic Swift type should comply to a protocol? -

i'd implement swift method takes in class type, takes instances of classes comply specific protocol. example, in objective-c have method:

- (void)addfilter:(gpuimageoutput<gpuimageinput> *)newfilter; 

where gpuimageoutput particular class, , gpuimageinput protocol. gpuimageoutput classes comply protocol acceptable inputs method.

however, automatic swift-generated version of above

func addfilter(newfilter: gpuimageoutput!) 

this removes requirement gpuimageoutput classes comply gpuimageinput protocol, allow non-compliant objects passed in (and crash @ runtime). when attempt define gpuimageoutput<gpuimageinput>, compiler throws error of

cannot specialize non-generic type 'gpuimageoutput'

how such class , protocol specialization in parameter in swift?

is swift must use generics, in way:

given these example declarations of protocol, main class , subclass:

protocol exampleprotocol {     func printtest()   // classes implements protocol must have method }  // empty test class class atestclass {  }  // child class implements protocol class atestclasschild : atestclass, exampleprotocol {     func printtest()     {         println("hello")     } } 

now, want define method takes input parameters of type atestclass (or child) conforms protocol exampleprotocol. write method declaration this:

func addfilter<t t: atestclass, t: exampleprotocol>(newfilter: t) {     println(newfilter) } 

your method, redefined in swift, should be

func addfilter<t t:gpuimageoutput, t:gpuimageinput>(newfilter:t!) {     // ... } 

edit:

as last comment, example generics on enum

    enum optionalvalue<t> {         case none         case some(t)     }     var possibleinteger: optionalvalue<int> = .none     possibleinteger = .some(100) 

specialized protocol conformance:

    enum optionalvalue<t t:gpuimageoutput, t:gpuimageinput> {         case none         case some(t)     } 

edit^2:

you can use generics instance variables:

let's have class , instance variable, want instance variable takes values of type atestclass , conforms exampleprotocol

class givemeageneric<t: atestclass t: exampleprotocol> {     var agenericvar : t? } 

then instantiate in way:

    var child = atestclasschild()     let agen = givemeageneric<atestclasschild>()     agen.agenericvar = child 

if child doesn't conform protocol exampleprotocol, won't compile