I have a large table designed to update a customers data protection preferences.
Some of the table is populated with reusable cells that contain a variable number of checkboxes, and depending on the json returned from the server, some of these checkboxes may be pre-checked.
When I pass the pre-checked state to the cell from tableView cellForRowAt all is well (checkboxes that are pre-checked are pre-checked). The problem I have is that these are reusable cells, and after a user has changed their selections, scrolling up or down the table triggers more calls to the setupCell function, which then resets the checkboxes to their original pre-checked state.
So, the question I have is...
What are the options for me to preserve a user’s selections after they have scrolled a table with resuable cells?
The switch statement in setupCell currently sets the pre-selections with the call to updateSelections(). Obviously this is the cause of the issue and I'm not entirely happy with placing logic directly in the cell anyway, but where is the best place to perform this logic only once? Or, is using reusable cells the wrong approach entirely to have pre-selections?
Any suggestions welcome. Here's a small code snippet to illustrate the point:
// UITableViewDataSource - passing the previous selections to setupCell in the UITableViewCell
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let viewModel = viewModels[indexPath.row]
switch viewModel {
case .preferences(let preferenceId, let titleText, let isEnabled):
guard let cell = tableView.dequeueReusableCell(withIdentifier: "Preferences") as? MarketingChannelPreferencesTableViewCell else {
return UITableViewCell()
}
cell.setupCell(id: id, text: text, isPreChecked: isPreChecked)
return cell
}
}
// UITableViewCell
func setupCell(id: String, text: String, isPreChecked: Bool) {
switch id {
case "email":
emailSelected = isPreChecked
updateSelections(id: id, isPreChecked: emailSelected)
case "post":
postSelected = isPreChecked
updateSelections(id: id, isPreChecked: postSelected)
case "text":
textSelected = isPreChecked
updateSelections(id: id, isPreChecked: textSelected)
default:
break
}
}
viewModels hold the information needed to setup each cell right? And you receive the viewModels from the service?
If so, when the user changes a specific checkbox, you should update the according viewModel. Thus, when you call setupCell inside cellForRowAt you should pass the updated info of each viewModel, resulting in the correct state of each checkbox.
You should make some action method for your checkbox buttons that you put on the MarketingChannelPreferencesTableViewCells and change your viewModels based on changing the value of these checkboxes. So when the cells data reload with user scrolling, cells show the new datas of viewModel
There're several ways.
I've created a small project maybe it will give you an solution to the problem.
https://drive.google.com/open?id=1d_RFdr6luNvRTdSC6XNE2vRWTi2IRyuT
Related
I want to populate a UITableView in Swift 4 and I want to just show records that belong to the user that is logged in. Obviously I require an IF statement to see whether two values are equal to each other. How do I return null as such, i.e. no cell is added to the table. Please see the code below
func tableView(_ tableView: UITableView,
cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let cell = tableView.dequeueReusableCell(withIdentifier:
"RunCell") as? RunCell else { return UITableViewCell() }
let user_id_main = String(MainMenuViewController.myVariables.user_id.prefix(2))
if (user_id_main==runs[indexPath.row].user_id)
{
cell.idLbl.text = "ID: " + runs[indexPath.row].run_id
cell.dateLbl.text = "Date: " + runs[indexPath.row].date_of_run
return cell
}
return cell
}
I know return cell outside of the IF still would return a cell, this is until I find an answer.
This is not the way UITableViews work. You can't decide on the fly if a cell is to be displayed or not. You need to do that before the table is loaded or reloaded.
Before the tableView is loaded or reloaded, filter your array into a new array that just contains records with the matching user_id. Then use this new array as the model for your table. The size of the new array will determine the number of rows in the table, and each row will correspond to one item of your new array.
Every time the user_id_main changes, refilter your runs array and reload the table.
you cannot return nil value cell,
to achieve what you want, first filter your runs array for the values you required and store in other array say mainUserRuns, then use this new array to provide data for your tableview.
I have been trying to change one of the cells in an NSTableView to a pull-down menu, but have been unsuccessful. I read the Apple developer documentation, but it doesn't give an example of how to use NSPopupButtonCell in a NSTableView. I searched forums, including here, and only found one somewhat relevant example, except that it was in objective-c, so it doesn't work for my swift app. Code for the table is here:
extension DeviceListViewController:NSTableViewDataSource, NSTableViewDelegate{
// get the number of rows for the table
func numberOfRows(in tableView: NSTableView) -> Int {
return homedevices.count
}
// use the data in the homedevices array to populate the table cells
func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView?{
let result = tableView.make(withIdentifier: (tableColumn?.identifier)!, owner: self) as! NSTableCellView
if tableColumn?.identifier == "ID" {
result.textField?.stringValue = homedevices[row].id
} else if tableColumn?.identifier == "Name" {
result.textField?.stringValue = homedevices[row].name
result.imageView?.image = homedevices[row].image
} else if tableColumn?.identifier == "Type" {
result.textField?.stringValue = homedevices[row].type
} else if tableColumn?.identifier == "Button" {
result.textField?.integerValue = homedevices[row].button
}
return result
}
// facilitates data sorting for the table columns
func tableView(_ tableView: NSTableView, sortDescriptorsDidChange oldDescriptors: [NSSortDescriptor]) {
let dataArrayMutable = NSMutableArray(array: homedevices)
dataArrayMutable.sort(using: tableView.sortDescriptors)
homedevices = dataArrayMutable as! [HomeDevice]
tableView.reloadData()
}
}
I really just want to be able to allow pull-down selection to change the button assigned to a particular homedevice (a simple integer), instead of having to type a number into the textfield to edit this value. Unfortuantely, when I add the popupbuttoncell to my table in IB, all of the views for my table cells are removed. So I may need to create the table differently. But most of the things I have read about and tried have caused runtime errors or display an empty table.
EDIT:
Day 3:
Today I have been reading here: https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/TableView/PopulatingViewTablesWithBindings/PopulatingView-TablesWithBindings.html
and many other places too, but I don't have rep to post any more links.
I have added a NSPopupButton in IB, but am not sure how to set the value. I tried result.objectValue = homedevices[row].button, but that does not work. I suppose that I need an array controller object. So then I tried creating an outlet for the object in my DeviceListViewController like #IBOutlet var buttonArrayController: NSArrayController! I guess that I now need to somehow find a way to connect the array controller to my homedevices array.
so I looked at example code here:
https://github.com/blishen/TableViewPopup
This is in objective-C, which is not a language I am using, but maybe if I keep looking at it at various times over the course of the week, I might figure out how to make a pull-down menu.
So I am continuing to work at this, with no solution currently.
This issue is solved, thanks to #vadian.
The button is inserted as NSPopUpButton object, rather than a NSPopUpButtonCell.
Then the cell gets its own custom class, which I called ButtonCellView as a subclass of NSTableCellView.
Then the created subclass can receive an outlet from the NSPopUpButton to the custom subclass. I can give this a selectedItem variable and create the menu here.
Then in the table view delegate, when making the table, I can just set the selectedItem of my ButtonCellView object to the value from my data array.
It works great!
Is it possible to check the Parse column "ID" for 0 (any number) then if 0 (the one in the column) equals indexPath.row 0 (the first cell) it displays the data from the row of 0 in Parse? The picture above is the class for the viewcontroller, the tableview cell data is in another class.
ID: number that will be checked with the indexPath.row
navTitle: navigation bar title
articleTitle: UILabel
written: UILabel
date: UILabel
article: UITextView
Edit for possible duplicate: It is not a duplicate, the other question answers how to move data from a cell to a view controller using prepareForSegue. This question is asking how, if possible, to check a column on Parse and if a number in that column matches an indexPath.row it will use the data from that row to which the number corresponds.
I now understand you would like to show the data that is appropriate for a given index path in a detail view controller, after they tap on the cell at said index path. This is assuming you are correctly showing the appropriate data in the table view, and now the question is how to obtain and show the relevant data for the row the user tapped on in a new view controller.
To do this, you could add an internal property to your detail view controller that is an Int. Set this property to the table view's selected index path's row before the detail view controller is shown, perhaps in prepareForSegue for example.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let detailVC = segue.destinationViewController as? DetailViewController {
if let selectedIndexPath = self.tableView.indexPathForSelectedRow {
detailVC.integerIdentifier = selectedIndexPath.row
}
}
}
Now in that detail view controller, you can access the property's value and query for the information you need from Parse given that value. (And you'll likely want to display some feedback to the user to inform them you're downloading the appropriate data to display.) For example, you could have the following code in a function you call from viewDidLoad:
let query = PFQuery(className: "eventsDetail")
query.whereKey("ID", equalTo: self.integerIdentifier)
query.getFirstObjectInBackgroundWithBlock { (detail: PFObject?, error: NSError?) -> Void in
//update your labels etc using the detail (Optional) PFObject
}
I want to note, importantly, that this is not a great way to store the data in Parse. One should not tie the data to how it will be displayed, which is the case here tying an identifier to the index path, forcing item with ID 0 to magically be the article details appropriate for the first cell in the table. You may wish to revisit the database design. For example, perhaps your other class that is used to generate a list of events could have a pointer to the event detail class, which would allow you to obtain the event details before you select an event and not have to query again for details.
Original Answer:
I understand you would like to show the data in this Parse class in your app in a table view, where the first table view cell displays the data for ID 0, the second cell displays the data for ID 1, etc.
To accomplish this, you'll want to query this class and apply an ascending order on the "ID" column. You will get back an array of PFObjects that are sorted as desired - lowest to highest ID, which you can use for your table view's data source to map them one-to-one.
Your query may look something like this:
let query = PFQuery(className: "Article")
query.orderByAscending("ID")
query.findObjectsInBackgroundWithBlock { (articles: [PFObject]?, error: NSError?) -> Void in
//use articles array as the data source, update the interface
self.articles = articles
self.tableView.reloadData()
}
Now in your table view data source methods, use this array to populate the table:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.articles.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let article = self.articles[indexPath.row]
//... configure cell, show article title, etc, return cell
}
I am in the process of creating a new tableviewcontroller however, I need this to be dynamic in a way that the layouts for each cell could change.
What I mean is that I am parsing news from JSON. Each news item could be of 3 types: Post, achievement, announcement. Each of these types contains different pieces of information. Post would have title, date, image and tags. Announcement would have the same but include an importance label. Achievement will have username, image, date, profile image, social sharing.
The news listing page will display all of the items but ordered by date but the layout for each of the types are completely different.
I have started and successfully got the below working:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if(indexPath.row == 0)
{
let cell: NewsPostTableViewCell = tableView.dequeueReusableCellWithIdentifier("newsPostTableCell") as! NewsPostTableViewCell
return cell
}
else
{
let cell: AchievementCardTableViewCell = tableView.dequeueReusableCellWithIdentifier("achievementCardTableCell") as! AchievementCardTableViewCell
return cell
}
}
to display 2 of the different layouts but I then started thinking, how will I be able to determine in the cellForRowAtIndexPath what layout to apply? Basically in the JSON response there will be a template identifier to notify the app which template to apply but just don't know how to apply this...if possible.
Would it be best to create 3 different view controllers 1 for each of the layouts and embed them?
Depending on how you are parsing the JSON you could store the type of cell into an Array. Then as you look into the array with indexPath.row based on the type it finds there you have it execute a Switch.
I'm a beginner, clearly out of my league and I haven't been able to find an answer online.
I have a UITableViewController with a UITableViewshowing custom objects stored in one array. I don't show all the object of the array in one single section of said TableView: the TableView has multiple sections, each containing a filtered portion of my objects array (I filter the custom objects array checking that the object category property is equal to a category that I specified in a categories array).
This filtering and showing the single array in different sections is working fine (I understand that maybe it's not elegant, as I said I'm a beginner in coding and I absolutely needed to work with one single array, without creating other arrays corresponding to the filtered results), but to better understand my issue I think it's better that I show what I did, so here's the TableView part of my code:
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return myCategoriesArray.count
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
for (var i = 0; i <= section; i++){
if section == i {
for eachCategory in myCategoriesArray {
return myObjectsArray!.filter() { $0.objectCategoryProperty == myCategoriesArray[i] }.count
}
}
}
// ...
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCellWithIdentifier("objectCell", forIndexPath: indexPath) as UITableViewCell
for (var i = 0; i <= indexPath.section; i++){
if indexPath.section == i {
for eachCategory in myCategoriesArray {
cell.textLabel?.text = myObjectsArray!.filter() { $0.objectCategoryProperty == myCategoriesArray[i] }[indexPath.row].nameProperty
return cell
}
}
}
// ...
}
This works in the sense that I have the UITableViewController showing all my objects, but filtered in separated sections by category.
My issue is with the segue when I select a cell and show a detail view.
Here's my prepareForSegue method:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
var nextVC = segue.destinationViewController as MyNextViewController
if let indexPath = tableView.indexPathForSelectedRow() {
let selected = myObjectsArray![indexPath.row]
nextVC.passedObject = selected
}
}
}
I'm sure that many of you already see my issue: the object that I pass to the next ViewController is selected in the custom objects array using as index [indexPath.row], but indexPath.row starts at 0 for each section, so when I select an object its index in the TableView is not equal to the index in the custom objects array, meaning that I pass the wrong object.
Now, I'm stuck because I don't see a way to pass the right (meaning, selected) object to the next View Controller while preserving the fact that I'm working with only a single array.
I was toying with the idea of adding an objectIDString property to every object and a single var currentlySelectedObjectIDString that is set every time a cell is selected and try to pass to the next View Controller the object with the objectIDString property matching the currentlySelectedObjectIDString, but it looks like a bad idea to my inexperienced eyes and I'm actually not sure how I could accomplish that even if I wanted to (maybe implementing didSelectRowAtIndexPath:, but I have not been able to make it work).
Any help would be really appreciated, I've been stuck on this for so long I begin to question a) my sanity b)every decision I made so far in the project (meaning, the single array for all objects that is filtered in sections), but I'm already so invested in it that I really would like not to have to start over.
Thank you,
Cesare
P.S. I hope my question is clear, english isn't my main language... sorry for any mistake!
I suggest you, to use a NSFetchedResultsController. This class have a property sectionNameKeyPath. In this property you could set your category and you won't need more iterate with a repetition in each numberOfSection and numberOfRows.
like this:
let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: moc, sectionNameKeyPath: "event.startDate", cacheName: nil)
In my case i need filter data by event.startDate.
I don't know if you are using core data, but if you are using, this is the better way to do this.
I'll expose them for you!
In the first moment NSFetchedResultsController like complicated, but its very very useful. Don't be afraid.
I don't know exactly your model and data. In this case i'll show you my owner sample.
Please see my question in the following link:
Sectioning TableView and rows with Core Data Swift
In this link, see my question, and in the bottom i'll explain the complete solution with the others answer.
If this is not clear for you, please, talk with me :.)
I spent all day trying to figure out a way to solve my own question above and I think I've finally found a working-workaround.
My premise and disclaimer is that this is a pile of hacks, I post this only in case this might help someone in my situation in the future, but clearly the way to deal with this kind of situation is Core Data, as suggested by Weles' answer, not what I did.
Here's briefly what I've done to get my multi-component UITableView, in which all the data come from a single array of custom objects that is filtered by a different value in every component, to pass the selected object to the detail view when a cell is selected.
1) I added to all my customObjects an objectID : String computed property (current date + random number).
2) I added a var currentlySelectedObjectID : String? in my TableViewController.
3) I subclassed UITableViewCell, creating a CustomTableViewCell class that only adds to the normal class a var selectedCellID : String?, then I changed my cellForRowAtIndexPath to return a CustomTableViewCell instead of a UITableViewCell. Inside this method, before returning the cell, I also set the property selectedCellID of the cell equal to objectID of the current object. I also had to change the class of the cell in the Storyboard from UITableViewCell to CustomTableViewCell.
4) In the Storyboard I removed the segue from the cell to the detailViewController that was automatically created by Xcode and I set a custom StoryboardID to the detailViewController ("detailVC"),
5) Inside didSelectRowAtIndexPath of TableViewController I did all the work that before I was trying to do in prepareForSegue, but in a different way (not a segue, a self.navigationController?.pushViewController). Here's the code:
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let indexPath = tableView.indexPathForSelectedRow();
let currentCell = tableView.cellForRowAtIndexPath(indexPath!) as CustomTableViewCell!;
self.currentlySelectedObjectID = currentCell.selectedCellID
// detailViewController instance
var detailVC = self.storyboard?.instantiateViewControllerWithIdentifier("detailVC") as MyDetailViewController
// I filter my objects array to "extract" the object with the objectID property equal to the currentlySelectedObjectID property (which is equal to the currentCell.selectedCellID, as set above). This array must have only 1 value. If so, I set the property passedCustomObject that I have in my detailViewController to the same object selected.
if (myObjectsArray!.filter() { $0.objectID == self.currentlySelectedObjectID }).count == 1 {
detailVC.passedCustomObject = (myObjectsArray!.filter() { $0.objectID == self.currentlySelectedObjectID })[0]
} else {
println("Error passing the object selected in the TableView to the DetailView")
}
// I push the detailViewController on top of the stack
self.navigationController?.pushViewController(detailVC, animated: true)
}
I think there are very good chance that a decent programmer (I am not one, but I hope to become one some day), seeing what I did, could faint.
Again, I don't think anyone should do this, if you're in my same situation go straight to Core Data: I spent a day on this, there's good chance that in three or four I could have had Core Data working.
But still, as hacked and inefficient as this is, it works... I tested multiple times. So, having spent so much time and having found no useful similar previous answers online, I thought to post mine.
Don't do this, I'm really afraid this is easily breakable! :)
I still look forward to other answers, to learn from my numerous mistakes!