swift - Swift4中的completionHandler返回字符串
问题描述
我正在尝试构建一个小型货币转换器,问题是我的 completionHandler 不起作用。结果,输入的货币在函数执行后不会立即改变
我已经尝试实现一个completionHandler;然而,还没有成功
class CurrencyExchange: ViewController {
//Outlets
@IBOutlet weak var lblCurrency: UILabel!
@IBOutlet weak var segOutputCurrency: UISegmentedControl!
@IBOutlet weak var txtValue: UITextField!
@IBOutlet weak var segInputCurrency: UISegmentedControl!
//Variables
var inputCurrency: String!
var currencyCNY: Double!
var currencyEUR: Double!
var currencyGBP: Double!
var currencyJPY: Double!
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.isNavigationBarHidden = true
}
@IBAction func btnConvert(_ sender: Any) {
assignOutput()
if txtValue.text == "" {
self.lblCurrency.text = "Please insert value"
} else {
let inputValue = Double(txtValue.text!)!
if segOutputCurrency.selectedSegmentIndex == 0 {
let output = Double(inputValue * currencyCNY!)
self.lblCurrency.text = "\(output)¥"
} else if segOutputCurrency.selectedSegmentIndex == 1 {
let output = Double(inputValue * currencyEUR!)
self.lblCurrency.text = "\(output)€"
} else if segOutputCurrency.selectedSegmentIndex == 2 {
let output = Double(inputValue * currencyGBP!)
self.lblCurrency.text = "\(output)"
} else if segOutputCurrency.selectedSegmentIndex == 3 {
let output = Double(inputValue * currencyJPY!)
self.lblCurrency.text = "\(output)"
}
}
}
func assignOutput() {
let currencies = ["EUR", "JPY", "CNY", "USD"]
inputCurrency = currencies[segInputCurrency.selectedSegmentIndex]
Alamofire.request("https://api.exchangeratesapi.io/latest?base=\(inputCurrency!)").responseJSON { (response) in
let result = response.result
let jsonCurrencies = JSON(result.value!)
let dictContent = jsonCurrencies["rates"]
self.currencyCNY = dictContent["CNY"].double
self.currencyEUR = dictContent["EUR"].double
self.currencyGBP = dictContent["GBP"].double
self.currencyJPY = dictContent["JPY"].double
}
}
}
预期结果是每次调用 btnConvert 函数时,都会调用 assignInput 和 assignOutput 函数,并将变量设置为正确的值。我是初学者,所以任何帮助将不胜感激。
解决方案
您需要一个完成处理程序assignOutput()
,我还添加了最小错误处理以避免崩溃
//Variables
var inputCurrency = ""
var currencyCNY = 0.0
var currencyEUR = 0.0
var currencyGBP = 0.0
var currencyJPY = 0.0
@IBAction func btnConvert(_ sender: Any) {
assignOutput() { success in
if success {
if txtValue.text!.isEmpty {
self.lblCurrency.text = "Please insert value"
} else {
if let inputValue = Double(txtValue.text!) {
if segOutputCurrency.selectedSegmentIndex == 0 {
let output = Double(inputValue * currencyCNY)
self.lblCurrency.text = "\(output)¥"
} else if segOutputCurrency.selectedSegmentIndex == 1 {
let output = Double(inputValue * currencyEUR)
self.lblCurrency.text = "\(output)€"
} else if segOutputCurrency.selectedSegmentIndex == 2 {
let output = Double(inputValue * currencyGBP)
self.lblCurrency.text = "\(output)"
} else if segOutputCurrency.selectedSegmentIndex == 3 {
let output = Double(inputValue * currencyJPY)
self.lblCurrency.text = "\(output)"
}
} else {
self.lblCurrency.text = "Please enter a number"
}
}
} else {
self.lblCurrency.text = "Could not receive the exchange rates"
}
}
}
func assignOutput(completion: @escaping (Bool) -> Void) {
let currencies = ["EUR", "JPY", "CNY", "USD"]
inputCurrency = currencies[segInputCurrency.selectedSegmentIndex]
Alamofire.request("https://api.exchangeratesapi.io/latest?base=\(inputCurrency)").responseJSON { (response) in
if let result = response.result.value {
let jsonCurrencies = JSON(result)
let dictContent = jsonCurrencies["rates"]
self.currencyCNY = dictContent["CNY"].double
self.currencyEUR = dictContent["EUR"].double
self.currencyGBP = dictContent["GBP"].double
self.currencyJPY = dictContent["JPY"].double
completion(true)
} else {
completion(false)
}
}
}
推荐阅读
- high-level-architecture - HLA:FOM 与 SOM
- python - 将 Django 应用程序添加到已安装的应用程序并且无法迁移的问题
- python - VSCode 将 API 导入 Python 项目
- java - 在 Firebase 中启动数据 - Android
- angular - GET request with Basic Auth token using Angular 6 getting 404 but works fine on Postman
- java - Creating query criteria for finding documents has desired element inside of array of array in MongoDB
- c++ - 了解使用 ^= 反转字符串的 C++ 函数
- clojure - 从 Github 导入包的问题
- javascript - Angular 表单返回错误类型错误:“_co.service.formData 未定义”?
- javascript - 匹配用户名的正则表达式:最少 3 个字符,最多 20 个字符,字符之间可选下划线