Question

我想做的是将2个文本字段加在一起，但我想将一个非整数与一个整数加在一起。因此，我想沿着a + 2 = 5进行操作。我想将int a定义为等于3。因此a = 3，a + 2在文本字段中应等于5。

@IBOutlet var txt1 : UITextfield!
@IBOutlet var txt2 : UITextfield!
@IBOutlet var total : UITextfield!

@IBAction func addTogether() {
//if txt1 = a then txt1 = 3 
}

Answer 1

以下是一个演示程序，可以执行您描述的操作，而无需在文本字段中明确插入“ a”。有3个字段，其规则为a + b = sum。将修改其中的哪个取决于您正在编辑的字段。因此，如果先设置a，然后再设置b，您将看到sum被修改。如果您随后开始编辑sum，则会看到a已根据b和sum进行了修改。

所有操作仅在演示代码中完成，因此鼓励您创建一个新项目，并用此代码替换ViewController并尝试一下。我希望这足以使您走上所需的道路，但请注意，创建这样的系统通常需要完成许多工作。

import UIKit

class ViewController: UIViewController {

    private var firstField: UITextField!
    private var secondField: UITextField!
    private var sumField: UITextField!

    private var currentlyUsedField: UITextField?
    private var previouslyUsedField: UITextField?

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor(white: 0.92, alpha: 1.0)

        self.firstField = {
            let field = UITextField(frame: CGRect(x: 12.0, y: 60.0 + (44.0+12.0)*0.0, width: view.bounds.width-24.0, height: 44.0))
            field.keyboardType = .decimalPad
            field.backgroundColor = UIColor.white
            field.addTarget(self, action: #selector(onFieldDidChange), for: .editingChanged)
            view.addSubview(field)
            return field
        }()

        self.secondField = {
            let field = UITextField(frame: CGRect(x: 12.0, y: 60.0 + (44.0+12.0)*1.0, width: view.bounds.width-24.0, height: 44.0))
            field.keyboardType = .decimalPad
            field.backgroundColor = UIColor.white
            field.addTarget(self, action: #selector(onFieldDidChange), for: .editingChanged)
            view.addSubview(field)
            return field
        }()

        self.sumField = {
            let field = UITextField(frame: CGRect(x: 12.0, y: 60.0 + (44.0+12.0)*2.0, width: view.bounds.width-24.0, height: 44.0))
            field.keyboardType = .decimalPad
            field.backgroundColor = UIColor.white
            field.addTarget(self, action: #selector(onFieldDidChange), for: .editingChanged)
            view.addSubview(field)
            return field
        }()
    }

    private func convertStringToDouble(_ string: String?) -> Double? {
        // Maybe use some formatters here
        let number = NSDecimalNumber(string: string)
        let doubleNumber = number.doubleValue
        return doubleNumber.isNaN ? nil : doubleNumber
    }

    private func convertDoubleToString(_ value: Double) -> String {
        // Maybe use some formatters here
        return String(value)
    }

    @objc private func onFieldDidChange(_ sender: UITextField) {
        // Check if we need to update a chain of used fields
        if sender !== currentlyUsedField {
            previouslyUsedField = currentlyUsedField
            currentlyUsedField = sender
        }

        // At least 2 fields must have been modified
        guard let currentlyUsedField = currentlyUsedField, let previouslyUsedField = previouslyUsedField else { return }

        // We need to know if field we are modifying is a sum or not
        let fieldToModify = [firstField, secondField, sumField].filter { $0 !== currentlyUsedField && $0 != previouslyUsedField }.first!
        if fieldToModify === sumField {
            // Show the sum
            if let left = convertStringToDouble(previouslyUsedField.text), let right = convertStringToDouble(currentlyUsedField.text) {
                fieldToModify?.text = convertDoubleToString(left+right)
            } else {
                fieldToModify?.text = "UNDEFINED"
            }
        } else {
            let leftField: UITextField = fieldToModify == firstField ? secondField : firstField
            if let sum = convertStringToDouble(sumField.text), let subtract = convertStringToDouble(leftField.text) {
                fieldToModify?.text = convertDoubleToString(sum-subtract)
            } else {
                fieldToModify?.text = "UNDEFINED"
            }
        }
    }


}

将一个字符串和一个int一起添加为一个总int（Swift4）

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