kotlin - Kotlin:类型推断失败。预期的类型不匹配:推断的类型为Pair <String，Int>，但希望Pair <Product，Int>

Question

我想调用主要运行以下函数addToCart()的方法，但是会出现此类错误，请问我应该如何更改代码？
谢谢!

    fun addToCart(){
    println("Productname : ")
    var nameInput= readLine() ?: "-"
    println("Num of $nameInput ")
    var num = readLine()!!.toInt()
    var got : Product? = warehouse.getProductByName(nameInput)
    shoppingCart.addToList(nameInput, num)

}

class ShoppingCart () {
            private val productAndQuantityList = mutableListOf<Pair<Product, Int>>()
            fun addToList(name: String, quantity: Int){
                productAndQuantityList.add(Pair(name, quantity))
            }
        ....
        }

Answer 1

我认为您不需要在调用add之前进行空检查。

fun addProductToCart(shoppingCart: ShoppingCart, warehouse: Warehouse) {
    println("Product name: ")
    var productName_E = readLine() ?: "-"
    println("No. of $productName_E ")
    var num = readLine()?.toInt()
    var got: Product? = warehouse.getProductByName(productName_E)
    if (num != null && got != null) {
        shoppingCart.productAndQuantityList.add(Pair(first = got, second = num))
    }
}

您的ShoppingCart类应该类似于以下类。

class ShoppingCart {

    val productAndQuantityList = mutableListOf<kotlin.Pair<Product, Int>>()
    ...
}