Question

在我正在处理的项目的表格视图中，我一直在努力正确显示用户输入的值。

我获取用户输入值的方式是让用户在文本字段中输入信息（公司名称，股票代码和徽标的URL），然后在按下完成按钮时调用handleSave() ：

func handleSave() {

let newCompanyName = nameTextField.text
guard let newCompanyStockSymbol = stockTextField.text else {
    // handle the error how you see fit
    print("error getting text from field")
    return
}
let newCompanyLogo = logoTextField.text

var newCompanyStockPrice = ""

// Fetch stock price from symbol provided by user for new company
let url = URL(string: "https://query.yahooapis.com/v1/public/yql?q=select%20symbol%2C%20Ask%2C%20YearHigh%2C%20YearLow%20from%20yahoo.finance.quotes%20where%20symbol%20in%20(%22\(newCompanyStockSymbol)%22)&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
    if error != nil {
        print(error!)
    } else if let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 {
        let json = JSON(data: data!)
        if let quotes = json["query"]["results"]["quote"].array {
            for quote in quotes {
                let ask = quote["Ask"].stringValue
                newCompanyStockPrice = ask
            }
        }
    }
    self.viewController?.save(name: newCompanyName!, logo: newCompanyLogo!, stockPrice: newCompanyStockPrice)
    //self.viewController?.tableView.reloadData()
}
task.resume()



let cc = UINavigationController()
let companyController = CompanyController()
cc.viewControllers = [companyController]
present(cc, animated: true, completion: nil)
}

反过来调用此save函数，该函数将值保存到托管上下文中。

func save(name: String, logo: String, stockPrice: String) {

guard let appDelegate =
    UIApplication.shared.delegate as? AppDelegate else {
        return
}

let managedContext =
    appDelegate.persistentContainer.viewContext

let entity =
    NSEntityDescription.entity(forEntityName: "Company",
                               in: managedContext)!
let company = NSManagedObject(entity: entity,
                              insertInto: managedContext)


company.setValue(stockPrice, forKey: "stockPrice")
company.setValue(name, forKey: "name")
company.setValue(logo, forKey: "logo")


do {
    try managedContext.save()
    companies.append(company)
} catch let error as NSError {
    print("Could not save. \(error), \(error.userInfo)")
}

tableView.reloadData()
}

如果我在self.viewController?.save(name: newCompanyName!, logo: newCompanyLogo!, stockPrice: newCompanyStockPrice)函数中调用handleSave()时设置了断点，我可以看到所有这三件事（newCompanyName，newCompanyLogo和{{1} }）有价值。但是当我尝试在newCompanyStockPrice中设置它时，新公司不会出现在我的表格视图中：

cellForRow

编辑：override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return companies.count } override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath) as! Cell let company = companies[indexPath.row] let stock = company.value(forKey: "stockPrice") as? String // Company name labels cell.textLabel?.text = company.value(forKey: "name") as? String // Stock price underneath if let stock = stock { cell.detailTextLabel?.text = "Current stock price: \(stock)" } // Logos DispatchQueue.main.async { if let url = NSURL(string: (company.value(forKey: "logo") as? String)!) { if let data = NSData(contentsOf: url as URL) { cell.logoView.image = UIImage(data: data as Data) } else { cell.logoView.image = UIImage(named: "noImage") } } } return cell }

viewWillAppear

Answer 1

我建议将调用放在主队列上显式重新加载数据。在我看来，您正在func save(name: String, logo: String, stockPrice: String)完成处理程序中调用dataTask，然后在该线程上调用reloadData。

因此，在save函数中，将其包装成如下：

DispatchQueue.main.async { [weak self] in 
    self?.tableView.reloadData()
}

用户输入的值保存到Core Data（？）但未显示在表格视图中

1 个答案: