I have a rather strange case of downcasting failure that I cannot understand.
I have almost identical code in two UITableViewControllers. ProjectTableViewController displays list of Project, and its datasource is [Project]. NewsfeedsTableViewController displays list of Newsfeed, but Newsfeed can contain different types of source data, including Project.
Depending on the type of the source data, each cell of NewsfeedsTableViewController is downcasted to appropriate subclass of UITableViewCell.
ProjectTableViewCell a subclass of UITableViewCell, and is used in both ProjectTableViewController and NewsfeedsTableViewController.
Now the interesting thing is, the code works without issue in ProjectTableViewController but crashes in NewsfeedsTableViewController, giving following error message:
Could not cast value of type 'UITableViewCell' (0x102e68128) to 'sample_app.ProjectTableViewCell' (0x1010ce6d0).
I have following codes in each class:
ProjectTableViewController.swift
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let project = projects[indexPath.row]
let cell = tableView.dequeueReusableCellWithIdentifier("ProjectTableViewCell") as! ProjectTableViewCell
cell.projectTitle.text = project.title
cell.projectKeywords.text = project.keywords
return cell
}
NewsfeedsTableViewController.swift
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let newsfeed = self.newsfeeds[indexPath.row]
switch newsfeed.newsfeedableType {
case "Project":
let cell = tableView.dequeueReusableCellWithIdentifier("NewsfeedTableViewCell") as! ProjectTableViewCell
let source = newsfeed.newsfeedable as! Project
cell.projectTitle.text = source.title
cell.projectKeywords.text = source.keywords
return cell
default:
let cell = tableView.dequeueReusableCellWithIdentifier("NewsfeedTableViewCell")!
cell.textLabel!.text = newsfeed.newsfeedableType + String(newsfeed.id)
return cell
}
}
I would love to understand what's causing this issue.
The issue was solved by adding another prototype cell of ProjectTableViewCell to the NewsfeedsTableViewController, and using it to display Newsfeed with Project as source.
Which means I will have to add prototype cells for all the source data types, and then configure them on the storyboard. I'm not looking forward to doing that.
I thought I could duck-type through this all, but I guess Swift does not work like that.
Related
I'm trying to create an autocompleter using iOS 8, Swift and Xcode 6.3
I have a problem that I'm trying to solve, but I gave up... I hope someone can help here. The problem is that (custom) UITableViewCell's are not displaying when the initial dataSource is empty. When adding data to datasource and reloading the tableView, the cells SHOULD display, but they don't... At least, the first time they don't... A second time, they DO... When I initialize the table with non-empty data, the problem doesn't occur. I guess something goes wrong with dequeueReusableCellWithIdentifier. In beginning, no reusable cells are found, or something. But I don't know why...
Relevant code, in ViewController.swift:
// filteredWords is a [String] with zero or more items
#IBAction func editingChanged(sender: UITextField) {
autocompleteTableView.hidden = sender.text.isEmpty
filteredWords = dataManager.getFilteredWords(sender.text)
refreshUI()
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as! AutocompleteTableViewCell
cell.title.text = filteredWords[indexPath.row]
return cell
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return filteredWords.count
}
func refreshUI() {
self.autocompleteTableView.reloadData()
}
I created a sample project on github:
https://github.com/dirkpostma/swift-autocomplete
And a movie on YoutTube to show what goes wrong:
https://www.youtube.com/watch?v=ByMsy4AaHYI
Can anyone look at it and spot the bug...?
Thanks in advance!
You've accidentally hidden your cell.
Open Main.storyboard
Select Cell
Uncheck Hidden
Side note: As for why it's displaying the second time around with the cell hidden? It appears to be a bug. It should still be hidden (print cell.hidden, notice it's always true despite showing the text on the screen).
I think you need to change your code. Check out below code. It is because if you remember in Objective C you needed to check if the Cell was nil and then initialise it. The reuse identifier is usually reusing an already created cell, but on the first launch this does not work because there is no Cell to use. Your current code assumes always that the cell is created (re-used) because you are using ! in the declaration, so if you use the optional (?) it can be null and you then can create the cell
var cell = tableView.dequeueReusableCellWithIdentifier("Cell") as? AutocompleteTableViewCell
if cell == nil
{
//You should replace this with your initialisation of custom cell
cell = UITableViewCell(style: UITableViewCellStyle.Value1, reuseIdentifier: "CELL")
}
cell.title.text = filteredWords[indexPath.row]
return cell
I'm trying to use Realm in my UITableViewController and I'm running into issues whenever I try to find the object at a row index if I cast the object to its class (forgive me if I'm using the wrong terminology, I'm still pretty new to Swift, Realm ans iOS dev!)...
I have a Site class which looks like this, and the database has a few thousand entries:
class Site: RLMObject {
var id: String = ""
var name: String = ""
}
In my table view controller, when I try to fetch a Site based on its index in the result set to load into a cell, if I try to cast it to a Site object it's always nil! If I let it be set using AnyObject, then I can see that the correct site at that index has indeed been found.
I'm guessing the .name call on AnyObject is only working because AnyObject responds to .name, but it helps me to see that the index is correct and that the site does exist...
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
let allSites = Site.allObjects()
var any: AnyObject = allSites.objectAtIndex(UInt(indexPath.row))
var site = allSites.objectAtIndex(UInt(indexPath.row)) as? Site
println("With AnyObject: \(any.name)")
println("With casting: \(site?.name)")
return cell
}
The result of the print statements above look like this (for example on a site which is named 'Addeboda'):
With AnyObject: Addeboda
With casting: Optional("")
Am I doing something wrong? I've googled around a bit, and all the tutorials and answers I can find along similar lines suggest that results.objectAtIndex(index) as Class should be the right approach.
No cast needed
It seems that casting to Site is not needed. This works fine:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
let allSites = Site.allObjects()
let site: AnyObject! = allSites[UInt(indexPath.row)]
cell.textLabel!.text = site.name
println("Site is: \(site.id)")
return cell
}
Seems to be a bug with either Swift or Realm. I'm guessing one of them gets confused when downcasting AnyObject! to something.
Initializing a new instance with correct type
However, if you really need to use the Site model class you can initialize a new RLMObject from the result:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
let allSites = Site.allObjects()
let site = Site(object: allSites[UInt(indexPath.row)])
cell.textLabel!.text = site.name
println("Site is: \(site.id)")
return cell
}
First try
It is unfortunate to hear that you are having issues with Realm and Swift. I am by no means a Swift pro, but it looks like you are casting site to an optional, and the result of using the optional cast operator site?.name is also an optional. Hence getting Optional("").
Can you try to see if you have any better luck with the following?
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
let allSites = Site.allObjects()
if var site = allSites[UInt(indexPath.row)] as? Site {
println("Site is: \(site.name)")
} else {
println("it not castable to Site. It is: \(toString(allSites[UInt(indexPath.row)].dynamicType))")
}
return cell
}
Also, you can use yourObject.dynamicType to get a reference to the objects real class type.
Best of luck
Here is some code from the tableview sample project:
class TableViewController: UITableViewController {
var array = DemoObject.allObjects().sortedResultsUsingProperty("date", ascending: true)
...
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as Cell
let object = array[UInt(indexPath.row)] as DemoObject
cell.textLabel?.text = object.title
cell.detailTextLabel?.text = object.date.description
return cell
}
}
You should be able to cast on the line you are storing that indexPath.row object
I am trying to create a database-based application for iOS and I am, more or less, forced to use Xcode 6.2 Beta 3, because I started the project with 6.2 and run iOS 8.2 on my testdevice. I have by the way figured out that the beta forces me to use the standard keypad, instead of decimal pad, otherwise the app stops working.
I can´t figure out what is wrong. And when I try to comment the function out something is still wrong in this file. Are there any missing connections between the VC-swift-file, tableVC-swift-file and datamodel-file?
I changed the name of the entity list once, and then changed back, because of another error I had before. But after I did it seems like the debug area doesnt catch the data I try to save to the database either...
The error says "Bound value in a conditional binding must be of Optional type"
Here is the code that is marked red on the initial line:
if let ip = indexPath {
var data: NSManagedObject = tankningslista[ip.row] as NSManagedObject
cell.textLabel?.text = data.valueForKey("datum") as String
}
The whole function looks like this:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Configure the cell...
let CellID: NSString = "Cell"
var cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
if let ip = indexPath {
var data: NSManagedObject = tankningslista[ip.row] as NSManagedObject
cell.textLabel?.text = data.valueForKey("datum") as String
}
return cell
}
I have followed this tutorial: https://www.youtube.com/watch?v=4ymz6i07DRM
try this way without using condition:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Configure the cell...
let CellID: NSString = "Cell"
var cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
var data: NSManagedObject = tankningslista[indexPath.row] as NSManagedObject
cell.textLabel.text = data.valueForKey("datum") as? String
return cell
}
I'm trying to make an app for iOS 8, using swift. The goal here is to make a kind of news feed. This feed displays posts from users, which follows a certain pattern.
I thought of using the UITableView where each cell follows a custom layout. The problem appears when I try to access a text label inside it. I try to access it by its tag, but when I do it, the whole app crashes. The error reported is "Swift dynamic cast failed", and I'm using the following code to access the view:
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {
let cellId: String = "cell"
var cell : UITableViewCell = tableView.dequeueReusableCellWithIdentifier(cellId) as UITableViewCell
if let ip = indexPath{
cell.textLabel.text = myData[ip.row] as String
var lbl = cell.contentView.viewWithTag(0) as UILabel
lbl.text = "ola"
}
return cell
}
Am I doing something wrong? Thanks in advance!
i think the Problem is the Tag 0. All Views are on default value 0. So try another tag value.
Just faced the same issue. The solution was to change tag to 10 and 20. I used 1 and 2 before. Is anybody aware of a range of tags that is used by the system?
So my 'cellForRowAtIndexPath' for a table with an image and a label per row looks like this now:
internal func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if let cell = tableView.dequeueReusableCellWithIdentifier("cellIdentifier") as? UITableViewCell {
(cell.contentView.viewWithTag(10) as UIImageView).image = IMAGES[indexPath.row]
(cell.contentView.viewWithTag(20) as UILabel).text = LABELS[indexPath.row]
return cell
} else {
NSLog("Prototype did not work")
return UITableViewCell(style: UITableViewCellStyle.Default, reuseIdentifier: "errorIdentifier")
}
}
Change the 0 to 1 or another tag, it work for me.
0 is overlapping to another cell label's tag.
I am new to IOS programming and will need some direction here.
I am trying to create a tableview with each rows having a image and some text.
I am able to take a TableViewController and programmatically was able to add basic text and rows. But can you please tell me how should i add more complex content. Trying to achieve something like this using program.
My current code looks like this in my TableViewController and its able to print a text message on each row.
override func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
return 1
}
override func tableView(tableView: UITableView?, numberOfRowsInSection section: Int) -> Int {
return 10
}
override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell? {
var mycell:UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("frontcell", forIndexPath: indexPath) as UITableViewCell
mycell.textLabel.text = "Just a generic message"
return mycell
}
There is a
mycell.contentView
which takes in UIView. But how does it works? How should this object be created?
Appreciate your help.
------Update -----
Thanks to Suryakant for helping out. Answer below for his step by step how to do. Any one who needs the source code can use this. http://pastebin.com/ZfNqK4tW
Though you can achieve it by default UITableViewCell also, as #meda mention in his answer,
but it seems, you want different UIImageView size and 2 UILabels with different font size or may be some more controls there. For Achieving that you need to customize UITableViewCell and you can do that by subclassing UITableViewCell class.
Create a class by subclassing UITableViewCell.
e.g. your subclass say MyCell look like —
2.Go to storyboard and select prototypeCell and select Identity inspector, in Class type your custom class name (e.g MyCell )in place of UITableViewCell.
drag-n-drop all the controls you need and link with their IBOutlets (From MyCell to prototypeCell).
This goes as below..
3.Now goto Attributes Selector and give some Identifier to your MyCell, you can give any string you want.
4.Goto the class where you implemented UITableView delegates and update your cellForIndexPath as bellow
override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath:
NSIndexPath!) -> UITableViewCell! {
let kCellIdentifier:String = "cell"
var cell = tableView.dequeueReusableCellWithIdentifier(kCellIdentifier) as MyCell!
if cell == nil {
// register Custom UITableView Class to UITableView
tableView.registerClass(MyCell.classForCoder(), forCellReuseIdentifier: kCellIdentifier)
cell = MyCell(style: UITableViewCellStyle.Default, reuseIdentifier: kCellIdentifier)
}
if var label = cell.cellMyCity{
label.text = cityList[indexPath.row]
}
if var label = cell.cellMyCountry{
label.text = countryList[indexPath.row]
}
if var imageView = cell.imageView{
imageView.image = UIImage(named :"img.png")
}
return cell
}
For reference you can see example code here.
You would create a subclass of UITableViewCell and then assign values to the property of your cell
mycell.textLabel.text = "Just a generic message"
mycell.detailTextLabel.text = "Just a detail message"
mycell.imageView.text = myImage
And for that you would use only one prototype Cell no need to duplicate them.