Question

我想解决我的问题。

我在Xcode中有文本字段，我想Xcode计算用户输入的字符串：

var x = 1
var y = 2

像这样我想如果用户在文本字段中输入xy，则Xcode计算如下：1+2

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet var label1: UILabel!
    @IBOutlet var label2: UILabel!
    @IBOutlet var label3: UILabel!
    @IBOutlet var label4: UILabel!
    @IBOutlet var tex1: UITextField!
    @IBOutlet var tex2: UITextField!
    override function viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        tex1.delegate = self
        tex2.delegate = self
    }

    override function didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    function textFieldShouldReturn(_ textField: UITextField) -> Bool{
        tex1.resignFirstResponder()
        tex2.resignFirstResponder()
        return true
    }

    @IBAction function close(_ sender: UIButton) {
        tex1.resignFirstResponder()
        tex2.resignFirstResponder()
    }

    @IBAction function pushAction(_ sender: UIButton) {
        label4.text = String(Int(tex1.text)+Int(tex2.text))
    }
}

Answer 1

    var temp = 0
    var prevCount = -1
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

        var txtAfterUpdate:NSString = textField.text! as NSString
        txtAfterUpdate = txtAfterUpdate.replacingCharacters(in: range, with: string).trimmingCharacters(in: CharacterSet.whitespacesAndNewlines) as NSString
        let newString:String! = String(txtAfterUpdate)
        if(prevCount > newString.characters.count - 1){
            if(newString.characters.count - 1 != -1){

                self.enterAmount =   self.enterAmount - Double(textField.text![(textField.text?.characters.count)! - 1])!

            }else{
                self.enterAmount = 0
            }

        }else{

            self.enterAmount = Double(newString[newString.characters.count - 1])! +  self.enterAmount

        }
        print("YOUR TOTAL \(self.enterAmount)")
        prevCount = newString.characters.count - 1


        return true
    }

extension String{
      subscript(i: Int) -> String {
        guard i >= 0 && i < characters.count else { return "" }
        return String(self[index(startIndex, offsetBy: i)])
    }
    subscript(range: Range<Int>) -> String {
        let lowerIndex = index(startIndex, offsetBy: max(0,range.lowerBound), limitedBy: endIndex) ?? endIndex
        return substring(with: lowerIndex..<(index(lowerIndex, offsetBy: range.upperBound - range.lowerBound, limitedBy: endIndex) ?? endIndex))
    }
    subscript(range: ClosedRange<Int>) -> String {
        let lowerIndex = index(startIndex, offsetBy: max(0,range.lowerBound), limitedBy: endIndex) ?? endIndex
        return substring(with: lowerIndex..<(index(lowerIndex, offsetBy: range.upperBound - range.lowerBound + 1, limitedBy: endIndex) ?? endIndex))
    }
}

Answer 2

你可以像这样使用

template<typename Base, typename Concrete>
std::list<Concrete*> downcast_list (std::list<Base*> const & bases) {
 std::list<Concrete*> result;
  for (auto const base_ptr : bases) {
    Concrete * concrete_ptr = dynamic_cast<Concrete*>(base_ptr);
    if (concrete_ptr != nullptr) {
      result.push_back(concrete_ptr);
    } else {
      // Error or ignore?
    }
  }
  return result;
}

如何通过Xcode 8.3.3计算文本字段中的字符串

2 个答案: