Swift: How to pass the Generic protocol as a parameter for another protocol

Question

I want to pass Generic protocol as a parameter for another protocol.

protocol OperationDelegate {
    associatedtype T
    func onOperationFinished(result:Array<T>)
    func onOperationError(error:OperationError, errorMessage:String)
}


protocol ResultDelegate {

    func findResult(query: String,odelegate: OperationDelegate<MyOwnDataType>)

}

How to pass the Generic protocol as a parameter for another protocol

I got following error

Protocol 'OperationDelegate' can only be used as a generic constraint because it has Self or associated type requirements

https://stackoverflow.com/questions/36348061/protocol-can-only-be-used-as-a-generic-constraint-because-it-has-self-or-associa — Muhammad Zohaib Ehsan, Mar 13 '19 at 08:57
@SachinVas How can I create Generic Protocol using another generic protocol as parameter? — Sridhar, Mar 13 '19 at 09:18

score 0 · Accepted Answer · edited Mar 13 '19 at 10:02

protocol OperationDelegate {
    associatedtype T
    func onOperationFinished(result:Array<T>)
    func onOperationError(error: Error, errorMessage:String) 
}

protocol ResultDelegate {
    func findResult<OpDelegate: OperationDelegate>(query: String, odelegate: OpDelegate) 
}

//Added few PlayGround works

    class ResultsFinder: ResultDelegate {



    func findResult<OpDelegate>(query: String, odelegate: OpDelegate) where OpDelegate : OperationDelegate {

        print(#function)
        // Do some operations
        let s1 = Student()
        s1.name = "one"
        let s2 = Student()
        s2.name = "two"

        let addressList = [s1,s2]
        odelegate.onOperationFinished(result: addressList as! [OpDelegate.T])

    }
}

also

class ResultDisplay: OperationDelegate {

    typealias T = Student

    func onOperationFinished(result: [Student]) {
        // Display address
          print(#function)
    }


    func onOperationError(error: Error, errorMessage: String) {
        // Display error
          print(#function)
    }

}

class Mainfunction {

let resultDisplay = ResultDisplay()
let finder = ResultsFinder()
func start() {

      print(#function)
    finder.findResult(query: "Sridhar", odelegate: resultDisplay)

}

}

let main = Mainfunction()
main.start()

I suppose that to match the intended behaviour `findResult` should have a `where OpDelegate.T == MyOwnDataType` — DeFrenZ, Mar 13 '19 at 12:33

Swift: How to pass the Generic protocol as a parameter for another protocol

1 Answers1