ios – 删除Swift 3中的最后一个字符

我正在创建一个简单的计算器应用程序,目前正在努力删除我的按钮被点击时的最后一个字符.我正在使用dropLast()方法,但我一直收到错误

Missing Argument for parameter #1 in call

@IBAction func onDelpressed (button: UIButton!)  {
     runningNumber = runningNumber.characters.dropLast()
     currentLbl.text = runningNumber
}

解决方法

斯威夫特4(附录)

在Swift中,您可以在String实例上直接应用dropLast(),不再调用.characters来访问String的CharacterView：

var runningNumber = "12345"
runningNumber = String(runningNumber.dropLast())
print(runningNumber) // 1234

Swift 3(原始答案)

我假设runningNumber是一个String实例.在这种情况下,runningNumber.characters.dropLast()不是String类型,而是CharacterView：

let foo = runningNumber.characters.dropLast()
print(type(of: foo)) // CharacterView

在将String实例分配回String类型的属性之前,需要使用CharacterView实例化String实例,例如,

var runningNumber = "12345"
runningNumber = String(runningNumber.characters.dropLast())
print(runningNumber) // 1234

就是你的情况

@IBAction func onDelpressed (button: UIButton!)  {
  runningNumber = String(runningNumber.characters.dropLast())
  currentLbl.text = runningNumber
}