Kotlin：由具有具体化类型参数的函数覆盖

Question

I am trying to pass a generic object to an override method that implements methods from an interface .

Unfortunately, I am getting an error when attempting to implements this. The error is as follows:

Override by a function with reified type parameter

Heres is my code

class ServiceVolley : ServiceInterface {

    val TAG = ServiceVolley::class.java.simpleName
    val basePath = "http://192.168.68.104:3005/"

    override inline fun <reified T> post(
        resource: String,
        payload: JSONObject,
        crossinline onSuccess: (response: JSONObject?) -> Unit,
        crossinline onError: (statusCode: Int) -> Unit
    ) {
        val jsonObjReq = object : JsonObjectRequest(Method.POST, basePath + resource, payload,
            Response.Listener<JSONObject> { response ->
                Klaxon().parse<T>(response.toString())
                onSuccess(response)
            },
            Response.ErrorListener { error ->
                onError(error.networkResponse.statusCode)
            }) {
            @Throws(AuthFailureError::class)
            override fun getHeaders(): Map<String, String> {
                val headers = HashMap<String, String>()
                headers["Content-Type"] = "application/json"
                headers["withCredentials"] = "true"
                return headers
            }
        }

        BackendVolley.instance?.addToRequestQueue(jsonObjReq, TAG)
    }
}

interface ServiceInterface {
    fun <T> post(resource: String, payload: JSONObject, onSuccess: (response: JSONObject?) -> Unit, onError: (statusCode: Int) -> Unit)
}

and I call this function with the following

apiController.post<User>("user/sign-in", payload,
{ user: User? ->
    Log.d("RESPONSE", user.toString());
},
{ statusCode: Int ->
    Log.d("ERROR", statusCode.toString())
})

Answer 1

See this issue: Overridding by inline function should be a warning, overriding by a function with reified type parameter should be an error .

Basically: with virtual functions, which function is called is determined at runtime; so they can't be inlined because the compiler doesn't know which function to inline. When you do something like

interface A {
    fun f(t: Int)
}

class AImpl : A {
    override inline fun f(t: Int) {
        println(t.toString())
    }
}

val a: A = AImpl()
a.f(1)

the non-inlined version of AImpl.f gets called.

But functions with reified must be inlined, or it won't work. So they can't be used to override.