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
- }
