[Swift] Error handling

What to write in this article

How to write Swift error handling

Why I wrote this article

To check when you forget

Things not considered in this article

-Whether the variable name setting is appropriate -Properly implement class responsibilities -Whether the access modifier is appropriate

Contents of the code below

・ Set a discount rate (DiscountPercentage) for the product -Output an error when the discount rate is not set properly

Code example

import Foundation

enum ProductError: Error {
    case discountRateIsOverHundret
    case discountRateIsZero
    case discountRateIsMinus

    var description:String {
        switch self {
            case .discountRateIsOverHundret: return "Discount rate is 100%that's all"
            case .discountRateIsZero: return "Discount rate is 0%is"
            case .discountRateIsMinus: return "The discount rate is negative"
        }
    }
}

class Product {
    private var name:String
    private var price:Double
    private var memo:String

    init(name:String, price:Double, memo:String){
        self.name = name
        self.price = price
        self.memo = memo
    }

    public func getName() -> String { name }

    public func getPrice() -> Double { price }

    public func getMemo() -> String {  memo }

    public func getInfo(discountPercentage:Double) {
        do {
            try print("\(self.getName())Discounted price:\(self.getDiscountedPrice(discountPercentage:discountPercentage))Circle")
        } catch {
            let error = error as! ProductError
            print("\(self.getName())Check the discount rate settings:\(error.description)")
        }
    }

    public func getDiscountedPrice(discountPercentage:Double) throws -> Int {
    
        if discountPercentage == 0 { throw ProductError.discountRateIsZero }
        if discountPercentage >= 100 { throw ProductError.discountRateIsOverHundret }
        if discountPercentage < 0 { throw ProductError.discountRateIsMinus }
        
        let discountRate:Double = (100 - discountPercentage) / 100
        return Int(price * discountRate)
    }

} 

var product1 = Product(name:"Product 1",price:1000,memo:"Sales No.1")
product1.getInfo(discountPercentage:50)
var product2 = Product(name:"Product 2",price:1000,memo:"Can be stored at room temperature")
product2.getInfo(discountPercentage:0)
var product3 = Product(name:"Product 3",price:1000,memo:"Frozen product")
product3.getInfo(discountPercentage:100)
var product4 = Product(name:"Product 4",price:1000,memo:"Attention to us")
product4.getInfo(discountPercentage:-1)

Execution result

Product 1 Discounted price: 500 yen
Product 2 Check the discount rate setting: The discount rate is 0%is
Product 3 Check the discount rate setting: Discount rate is 100%that's all
Product 4 Check the discount rate setting: The discount rate is negative