尝试运行实例索引中的随机数，但出现索引超出范围错误

Question

我创建了一个结构来连接到 mysql 数据库，然后为它创建了一个实例。当我尝试运行一个随机数（在数组的大小内）时，我得到默认数 0，但我的数据库 ID 从 1 开始，因此我得到索引超出范围的错误。

import UIKit
struct PickUpLine: Decodable {
    let id: Int
    let setup: String
}

class PickUpLines: UIViewController {

    private var pul = [PickUpLine ] ()

    @IBOutlet var PULViewController: UIView!

    @IBOutlet weak var PULabel: UITextView!
    override func viewDidLoad() {
        super.viewDidLoad()


        downloadJson()

    }



    @IBAction func generateRandPUL(_ sender: Any) {

        showRandPUL ()

    }

    func showRandPUL (){

        let randomPUL = Int (arc4random_uniform(UInt32(pul.count)))
        PULabel.text = pul[randomPUL].setup // index out of range

    }

    func downloadJson () {
    let url = "https://icebreakerappinc.herokuapp.com/pickuplines"

    print(url)

    //creating let for the url to bond with the link above #2
    guard let url2  = URL (string: url) else {return}
    URLSession.shared.dataTask(with: url2) { (data,response,err) in
        guard let data = data else {return}

        do {
            let PULurl = try JSONDecoder().decode([PickUpLine].self, from: data)

            DispatchQueue.main.async {
                self.PULViewController.reloadInputViews()
                self.pul = PULurl
            }
        }catch let jsonErr {
            print("Error serializing json:" , jsonErr)
        }
        }.resume()

    }
}

Answer 1

只需在pularray上使用randomElement，

let randomPUL = pul.randomElement()
puLabel.text = randomPUL?.setup

Call randomElement() to select a random element from an array or another collection.

Returns

A random element from the collection. If the collection is empty, the method returns nil.

注意： 使用 camel case 命名变量。它应该是 puLabel 而不是 PULabel.

更新：

这是 PickUpLines 控制器的样子，

class PickUpLines: UIViewController {
    private var pul = [PickUpLine ] ()

    func showRandPUL (){
        let randomPUL = pul.randomElement()
        puLabel.text = randomPUL?.setup
    }
    //rest of the code...
}

Answer 2

试试这可能是它的工作

 guard let count = pul.count - 1 , count >= 0 else { return }
 let randomPUL = Int(arc4random_uniform(UInt32(count)))

尝试运行实例索引中的随机数，但出现索引超出范围错误

Trying to run random number in instance's index but i get index out of range error

mysql

struct

instance

swift

尝试 运行 实例索引中的随机数，但出现索引超出范围错误

Trying to run random number in instance's index but i get index out of range error

mysql

struct

instance

swift

尝试运行实例索引中的随机数，但出现索引超出范围错误