012_swift_捕获异常 do try catch

enum ErrorType:Error{
    case invalidProduct
    case insuffficientCoisn(coinsNeeded:Int)
    case outOfStock

    
}
struct Product {
    var price:Int
    var count:Int
}
var totalCoins=20
class Shop{
    var products=[
        "pudding":Product(price: 12, count: 7),
        "Donut":Product(price: 10, count: 4),
        "Cheesepuff":Product(price: 7, count: 13)
    ]
    func sell(ProductName:String) throws{
        guard let product=products[ProductName] else {
            throw ErrorType.invalidProduct
        }
        guard product.count>0 else {
            throw ErrorType.outOfStock
        }
        guard product.price<=totalCoins else {
            throw ErrorType.insuffficientCoisn(coinsNeeded: product.price-totalCoins)
        }
        totalCoins-=product.price
        var newItem=product
        newItem.count-=1
        products[ProductName]=newItem
        print(">>>>\(ProductName)")
    }
}
var shop=Shop()
do{
    //会抛出异常
   // try shop.sell(ProductName: "Apple")
     try shop.sell(ProductName: "pudding")
     try shop.sell(ProductName: "pudding")
}
catch ErrorType.invalidProduct{
    print("Invalid product.")
}catch ErrorType.outOfStock{
    print("Out of stock.")
}catch ErrorType.insuffficientCoisn(coinsNeeded: let coinsNeeded){
    print("Need an additional\(coinsNeeded) conin(s).")
}