如何在Swift中将自定义单元格的文本字段的文本设置为自定义对象数组内的变量？

Question

I have a table view with custom cells, and each cell has a text field. I want to take the text in the textfield and put it inside my [classes] : [ClassObject].title for each cell. The problem is that it won't work!

Here's the code

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "newCell")! as! EditCell
    let c = classes[indexPath.row]
    cell.titleTF.text = c.title
    c.title = cell.titleTF.text

    return cell
}

And heres the custom class object

class ClassObject: NSObject, NSCoding {

var title : String?
var detail : String?
var startTime : String?
var endTime: String?
var stuff : [String]?
var info : String?
var titleColor : UIColor?


enum state {
    case normal,red,yellow
}

func setStates(currentState : state) {
    switch currentState {
    case .normal:
        titleColor = UIColor.black
    case .red:
        titleColor = UIColor.red
    case .yellow:
        titleColor = UIColor(red: 203/255, green: 154/255, blue: 0/255, alpha: 1.0)
    }
}

init(title: String, detail: String, startTime: String, endTime: String, stuff: Array<String>, info: String, titleColor: UIColor) {
    self.title = title
    self.detail = detail
    self.startTime = startTime
    self.endTime = endTime
    self.stuff = stuff
    self.info = info
    self.titleColor = titleColor

}


required convenience init(coder aDecoder: NSCoder) {
    let title = aDecoder.decodeObject(forKey: "title")
    let detail = aDecoder.decodeObject(forKey: "detail")
    let startTime = aDecoder.decodeObject(forKey: "startTime")
    let endTime = aDecoder.decodeObject(forKey: "endTime")
    let stuff = aDecoder.decodeObject(forKey: "stuff")
    let info = aDecoder.decodeObject(forKey: "info")
    let titleColor = aDecoder.decodeObject(forKey: "titleColor")
    self.init(title: title as! String, detail: detail as! String, startTime: startTime as! String, endTime: endTime as! String, stuff: stuff as! Array<String>, info: info as! String, titleColor: titleColor as! UIColor)
}

func encode(with aCoder: NSCoder) {
    aCoder.encode(title, forKey: "title")
    aCoder.encode(detail, forKey: "detail")
    aCoder.encode(startTime, forKey: "startTime")
    aCoder.encode(endTime, forKey: "endTime")
    aCoder.encode(stuff, forKey: "stuff")
    aCoder.encode(info, forKey: "info")
    aCoder.encode(titleColor, forKey: "titleColor")
}
override init() {
    super.init()
}

}

At last heres the custom UITableViewCell

class EditCell: UITableViewCell {



@IBOutlet weak var titleTF: UITextField!




override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
}

override func setSelected(_ selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)

    // Configure the view for the selected state
}

}

Answer 1

Prerequisites

1. Is EditCell properly setup? ie can it display, say, a debug string:

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "newCell")! as! EditCell cell.titleTF.text = "debug row \\(indexPath.row)" return cell } 

2. Is your model properly setup? ie can you log its content:

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "newCell")! as! EditCell let c = classes[indexPath.row] print("c.title at index \\(indexPath.row): \\(c.title)") cell.titleTF.text = c.title return cell } 

---

Discussion

Assuming that you have an EditCell looking like this:

class EditCell : UITableViewCell {
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    var titleTF:UILabel
}

and a structure aClass defined more or less like that:

struct aClass {
    var title:String
}

and lastly an array of such aClass defined like so:

var classes:[aClass] = [aClass.init(title: "demo")]

then the code below cannot possibly compile unless you comment out c.title = ...

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "newCell")! as! EditCell
    let c = classes[indexPath.row]
    cell.titleTF.text = c.title
    ///c.title = cell.titleTF.text
    return cell
}

which leads to this analysis ; if you actually want to take the content of the cell and put it back into an array, as this sentence seems to imply:

I want to take the text in the textfield and put it inside my [classes] : [ClassObject].title for each cell.

the place to do so is not in dequeueReusableCell which is exactly the opposite. The only time to change your model is when the cell is changed, as cells are transient and reused, not persisting any data.

---

Conclusion

from comment

User Interface cells are transient, UI elements. They also are reused.
In other words, only the visible cells exist, if at all, and are recycled to display data.

You cannot cycle through the to get back to the data. You must store the user changes on the fly back into your model (or a copy of it), and positively do not rely on the view to store user data for you. This is the basis of MVC design: the model is the data.

The action of saving is the equivalent of committing the new model.

Hint: If you use NSFetchedResultsController , a lot of this boilerplate work is done by the OS.