从firstFile.swift/viewController调用secondFile.swivt/viewContro

Question

我正试图从第二个ViewController中生成的另一个函数()中调用第一个ViewController生成的函数()。

它是一个更新firstViewController中按钮标题的函数。

我找过了，但找不到路。

First ViewController//ViewController.swift

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
weightLabel.delegate = self
}


@IBAction func excerciseChooserButton(_ sender: UIButton) {
}
var weight = 0 {
didSet {
weightLabel.text = "(weight)"
}
}
// User input WEIGHT
@IBOutlet weak var weightLabel: UITextField!
func textField(_ weightLabel: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let isNumber = CharacterSet.decimalDigits.isSuperset(of: CharacterSet(charactersIn: string))
let withDecimal = (
string == NumberFormatter().decimalSeparator &&
weightLabel.text?.contains(string) == false
)
return isNumber || withDecimal
}

@IBAction func plusWeight(_ sender: UIButton) {
weight += 5
}
@IBAction func minusWeight(_ sender: UIButton) {
weight -= 5
}
// User input REPS

@IBOutlet weak var repLabel: UILabel!
@IBAction func repSlider(_ sender: UISlider) {
let currentRepValue = Int(sender.value)
repLabel.text = "(currentRepValue)"
let cm = Calculator(weight: weightLabel.text!, reps: repLabel.text!)
let result = cm.calcRM()
repMax.text = "1RM: (result)kg"
}

@IBOutlet weak var repMax: UILabel!
@IBOutlet weak var excerciseLabel: UIButton!
func changeText() {
excerciseLabel.setTitle(Excercises.excChosen, for: .normal)
print(excerciseLabel)
}

@IBAction func unwindToViewController(segue:UIStoryboardSegue) { 
}
}

///////

第二视图控制器//异常选择器ViewController.swift

import UIKit

struct Excercises {
static var excChosen:String? = ""
}
class ExcerciseChooserViewController: UIViewController, UITableViewDelegate, UITableViewDataSource

// Data model: These strings will be the data for the table view cells
let excercises: [String] = ["Bench Press", "Squat", "Push Press", "Deadlift"]
// cell reuse id (cells that scroll out of view can be reused)
let cellReuseIdentifier = "cell"
// don't forget to hook this up from the storyboard
@IBOutlet var tableView: UITableView!


override func viewDidLoad() {
super.viewDidLoad()
// Register the table view cell class and its reuse id
self.tableView.register(UITableViewCell.self, forCellReuseIdentifier: cellReuseIdentifier)
// (optional) include this line if you want to remove the extra empty cell divider lines
// self.tableView.tableFooterView = UIView()
// This view controller itself will provide the delegate methods and row data for the table view.
tableView.delegate = self
tableView.dataSource = self
}
// number of rows in table view
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.excercises.count
}
// create a cell for each table view row
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// create a new cell if needed or reuse an old one
let cell:UITableViewCell = self.tableView.dequeueReusableCell(withIdentifier: cellReuseIdentifier) as UITableViewCell!
// set the text from the data model
cell.textLabel?.text = self.excercises[indexPath.row]
return cell
}

// method to run when table view cell is tapped
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let excerciseChosen = "(excercises[indexPath.row])"
print("You tapped cell number (indexPath.row).")
print(excerciseChosen)
goBackToOneButtonTapped((Any).self)
Excercises.excChosen = excerciseChosen
print(Excercises.excChosen!)
// call function to update text
ViewController.changeText()

}


@IBAction func goBackToOneButtonTapped(_ sender: Any) {
performSegue(withIdentifier: "unwindToViewController", sender: self)
}
}

Answer 1

改为从unwindToViewController调用它，当第一个视图控制器不可见时无需调用它

Answer 2

有很多方法可以做到这一点，但我将在这里描述一个简单的方法。

因为您要通过segue返回"ViewController"，所以一个好的选择是覆盖prepare(for:sender:)。这将为您提供对该segue的目标视图控制器的引用，然后允许您在该视图控制器中调用函数或设置属性。你可以在这里阅读更多关于这种方法的信息。

以下是一些基本步骤：

1. 在ViewController中，更新changeText()方法以接受字符串参数：changeText(_ text: String?)
2. 向ExcerciseChooserViewController添加一个属性以容纳要使用的文本：private var chosenExercise: String?
3. 在tableView:DidSelectRowAtIndexPath:方法中，将新的chosenExercise属性设置为要传递给ViewController的字符串
4. 在ExcerciseChooserViewController的prepare(for:sender:)中，获取对目标视图控制器的引用，将其向下转换为子类ViewController，并调用传入exerciseText字符串的新方法

例如：

class ViewController: UIViewController, UITextFieldDelegate {
@IBOutlet weak var excerciseLabel: UIButton!
func changeText(_ text: String?) {
guard let text = text else { return }
excerciseLabel.setTitle(text, for: .normal)
print(excerciseLabel)
}
}

在ExcerciseChooserViewController:中

class ExcerciseChooserViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
private var chosenExercise: String?
// method to run when table view cell is tapped
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let excerciseChosen = "(excercises[indexPath.row])"
print("You tapped cell number (indexPath.row).")
print(excerciseChosen)
goBackToOneButtonTapped((Any).self)
Excercises.excChosen = excerciseChosen
print(Excercises.excChosen!)
chosenExercise = excerciseChosen
}
@IBAction func goBackToOneButtonTapped(_ sender: Any) {
performSegue(withIdentifier: "unwindToViewController", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destinationVC = segue.destination as? ViewController {
destinationVC.changeText(chosenExercise)
}
}
}