demo

demo.swift

import Combine

enum SDKError: Error{
    case err0
}

typealias OnSuccessCallback<T> = (_ result: T) -> Void
typealias OnFailureCallback = (_ error: SDKError) -> Void
struct APIDemo{
    func api1(param:String, onSuccess:OnSuccessCallback<Int>, onFailure: OnFailureCallback){
        if param == "1" {
            onSuccess(0)
        }
        onFailure(.err0)
    }
    func api2(param:Int, onSuccess:OnSuccessCallback<String>, onFailure: OnFailureCallback){
        if param == 1 {
            onSuccess("a")
        }
        onFailure(.err0)
    }
}

APIDemo().api1(param: "1") { (result) in
    print(result)
} onFailure: { (err) in
    print(err)
}


typealias APIFunc<T,U> = (T,OnSuccessCallback<U>,OnFailureCallback) -> Void
typealias APIRxFunc<T,U> = (T) -> AnyPublisher<U, SDKError>

func rx<T,U>(_ f: @escaping APIFunc<T,U>)->APIRxFunc<T,U> {
    return { (param:T) -> AnyPublisher<U,SDKError> in
        return Future(){ promise in
            f(param, {result in
                promise(.success(result))
            },{error in
                promise(.failure(error))
            })
        }.eraseToAnyPublisher()
    }
}

var bag:[AnyCancellable] = []


rx(APIDemo().api1)("")
    .map { (val) -> Int in
        val + 1
    }
    .flatMap(rx(APIDemo().api2))
    .sink { (comp) in
        print(comp)
    } receiveValue: { (val) in
        print(val)
    }.store(in: &bag)