ios - Cannot assign Generic value to protocol associatedType variable in an extension -

i have been struggling mind problem

i trying create bindings structure on swift, bind viewmodels , controllers in easy way. have created protocol defines variable stored on controller.

protocol dva_movver_viewcontrollerprotocoldelegate {     associatedtype delegatetype : dva_movver_viewmodelprotocol     var dva_viewmodeldelegate : delegatetype? { set } } 

as can see, variable restricted fulfill protocol, one:

protocol dva_movver_viewcontrollerprotocol {    func dva_tellviewmodel()    // other methods } 

i want controller classes implement variable, can stored variable. cannot accomplish using extension.

so, have extension second protocol implement bindings , create common method bind variable controller

extension  dva_movver_viewcontrollerprotocol self:dva_movver_viewcontrollerprotocoldelegate  {     mutating func dva_bindviewmodel<t:dva_movver_viewmodelprotocol>(parameter:t) {          typealias delegatetype = t         self.dva_viewmodeldelegate = parameter     }     ...    // rest of dva_movver_viewcontrollerprotocol methods }  

and here got stuck. compiler says “cannot assign value of type 't' type '_?’”. assume might because cannot resolve parameter type @ compile time, have no idea how solve this...

as stated @rbarbera, type erasure way go in cases:

https://realm.io/news/type-erased-wrappers-in-swift/