Swift：在点击时在表格视图中更改按钮图像

Question

I created an Xcode project for iPhone using Swift, with Parse for the backend. My current problem is with creating a todo list application as one tab of a larger application.

Inside of a custom prototype cell, I want to have a checkbox button that changes its image when clicked as well as changing the isChecked:Bool variable for that cell. I've gotten most of the way there, but I've run into a brick wall regarding setting and accessing the appropriate variables for this button.

Edit: Thanks to the answer below and other resources, I have finally written working code for this checkbox functionality. Essentially, the button's tag property is set equal to the indexPath.row of the PFObject. As my original question was a bit broad, I am updating my code below so that it might help other new developers who are working on similar functionality. There may be better ways, but this seems to work.

// TasksVC.swift

var taskObjects:NSMutableArray! = NSMutableArray()

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)    
    self.fetchAllObjects()
}

func fetchAllObjects() {

    var query:PFQuery = PFQuery(className: "Task")

    query.whereKey("username", equalTo: PFUser.currentUser()!)

    query.orderByAscending("dueDate")
    query.addAscendingOrder("desc")

    //fetches values within pointer object
    query.includeKey("deal")

    query.findObjectsInBackgroundWithBlock { (tasks: [AnyObject]!, error:NSError!) -> Void in

        if (error == nil) {

            var temp:NSArray = tasks! as NSArray
            self.taskObjects = temp.mutableCopy() as NSMutableArray

            self.tableView.reloadData()

            println("Fetched objects from server")

        } else {
            println(error?.userInfo)
        }
    }
}


//MARK: - Tasks table view
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return self.taskObjects.count
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = self.tableView.dequeueReusableCellWithIdentifier("TaskCell", forIndexPath: indexPath) as TaskCell

    var dateFormatter:NSDateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "M/dd/yy"

    var task:PFObject = self.taskObjects.objectAtIndex(indexPath.row) as PFObject

    cell.desc_Lbl?.text = task["desc"] as? String
    cell.date_Lbl.text = dateFormatter.stringFromDate(task["dueDate"] as NSDate)

    //value of client within Deal pointer object
    if let deal = task["deal"] as? PFObject {
        // deal column has data
        if let client = deal["client"] as? String {
            // client has data
            cell.client_Lbl?.text = client
        }
    }

    //set the tag for the cell's UIButton equal to the indexPath of the cell
    cell.checkbox_Btn.tag = indexPath.row
    cell.checkbox_Btn.addTarget(self, action: "checkCheckbox:", forControlEvents: UIControlEvents.TouchUpInside)
    cell.checkbox_Btn.selected = task["isCompleted"] as Bool

    if (task["isCompleted"] != nil) {
            cell.checkbox_Btn.setBackgroundImage(UIImage(named:(cell.checkbox_Btn.selected ? "CheckedCheckbox" : "UncheckedCheckbox")), forState:UIControlState.Normal)
    }

    cell.selectionStyle = .None

    return cell

}

func checkCheckbox(sender:UIButton!) {
    var senderBtn:UIButton = sender as UIButton
        println("current row: \(senderBtn.tag)")

    //retrieve the PFObject for the row we have selected
    var task:PFObject = self.taskObjects.objectAtIndex(senderBtn.tag) as PFObject
        println("objectID: \(task.objectId)")

    if task["isCompleted"] as NSObject == true {
            task["isCompleted"] = false
        } else {
            task["isCompleted"] = true
        }

    task.saveInBackgroundWithBlock { (success, error) -> Void in

        if (error == nil) {
            println("saved checkbox object in background")
        } else {
            println(error!.userInfo)
        }
    }

    self.tableView.reloadData()
}

override func tableView(tableView: UITableView?, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
    return true
}

override func tableView(tableView: UITableView?, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {

    if (editingStyle == UITableViewCellEditingStyle.Delete) {

        var task:PFObject = self.taskObjects.objectAtIndex(indexPath.row) as PFObject

        task.deleteInBackgroundWithBlock({ (success, error) -> Void in

            self.fetchAllObjects()

            self.taskObjects.removeObjectAtIndex(indexPath.row)
        })

    } else if editingStyle == .Insert {

    }
}

Answer 1

When working with tables and collection views, all the objects you have in a custom cell can be easily accessed in cellForRowAtIndexPath (for UITables)

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    var cell = tableView.dequeueReusableCellWithIdentifier("ActionCell", forIndexPath: indexPath) as ActionCell

    var action = actions[indexPath.row] as Action

    cell.nameLabel?.text = action.name
    cell.listLabel?.text = action.list
    cell.dateLabel?.text = action.date
    cell.checkboxButton = action.isChecked
    cell.checkBoxButton.setImage(UIImage(named:"checkedImage"), forState:UIControlState.Normal)
    return cell
}

more over I would suggest to change constants to variables. I'm new to Swift too and "let" declares a static variable.

I find very cool the use of the conditional operator (?:) in these cases:

cell.checkBoxButton.setImage(UIImage(named:(any_boolean_condition ? "checkedImage" : "uncheckedImage")), forState:UIControlState.Normal)

so it can return one image name for the condition True and another name for the condition False.