In my app's chat feature, I use a UITableView to present chat history.
Cells are subclasses of UITableViewCell. The class receives a Chat object that contains all the info it needs to build the cell.
I have a Firebase listener that fires when the "last message" is changed. It changes a UILabel text to "new Message!" and then a protocol/delegate reloads the table view. Now I need to change the label back to "".
When the user clicks the cell, I use didSelectRowAt to segue to JSQMessagesViewController after preparing for segue. My idea is to use prepare for segue or even didSelectRowAt itself to change a Boolean variable in the UITableViewCell that corresponds to that chat Object. Navigating back to the tableViewController will trigger reloadData.
Each ChatObject has a unique ID that I can access. After firing the listener, I will set this Boolean to one value. After clicking the cell, I will set it to another. the state of the variable will tell the IBOutlet what text to show. In the UITableViewCell class, I use:
var chat: Chat! {
didSet {
self.updateUI()
}
}
}
So in self.updateUI() I make necessary changes, but can I make properties in the UITableViewCell mutable/visible from the UITableViewController?
How can I make properties in the UITableViewCell that are mutable from the UITableViewController
You don't. You make changes in your model and tell the table view to reload its data.
So in self.updateUI() I make necessary changes, but can I make properties in the UITableViewCell mutable from the UITableViewController?
I don't think you're trying to do what you say you are. In the case that you are trying to access the properties of your custom UITableViewCell subclass, you might want to use cellForRowAtIndexPath(). Then cast the result to whatever class name you have for your UITableViewCell subclass.
Example:
If I want to change the 5th row outside of our table view dataSource, I could do something like this.
let fifthIndexPath = IndexPath(row: 5, section: 0)
let thisCell = myTableView.cellForRowAtIndexPath(at indexPath: fifthIndexPath) as! MyCustomTableViewCell
thisCell.property = value
See:
https://developer.apple.com/documentation/uikit/uitableviewdatasource/1614861-tableview
Related
I've got a collection view with multiple cells created programically. I want to update a variable to a different value when the user taps a specific cell. So eg: Cell 1 is tapped -> var test = "cell1" , cell2 is tapped var test = "cell2". Usually I'd just create an IBAction by dragging from the storyboard but I'm not sure how to do it in this case.
I'm using Swift 3.1
To add interactivity to UITableViews, UICollectionViews, and other kinds of views which display collections of data, you can't use Storyboard actions, as the content is generated dynamically during runtime, and the Storyboard can only work for static content.
Instead, what you need to do is set your UICollectionView's delegate property to an object that implements the UICollectionViewDelegate protocol. One of the methods defined as part of the protocol is the collectionView(_:didSelectItemAt:) method. This method will get called whenever the user selects (taps) a collection view cell with the IndexPath to that cell as an argument. You can update your variable in that method. Just remember to deselect the cell after handling the tap by using the deselectItem(at:) method on your UICollectionView.
There are UICollectionView delegate that you need to implement. It goes like this
did select item at index path will give index path of the cell that was selected. Using indexpath or any other property of the data source array you are using, you can modify the variable value.
override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
if let cell = collectionView.cellForItemAtIndexPath(indexPath) {
//check your condition and modify the variable value depending on index path or any other property you are referring to.
}
}
I am trying to implement a table view design where a user can click a button outside of a table view cell and the display mode of all the buttons should change. However this is not the 'selected' mode for a given cell (that will be yet a third state that becomes accessible via switching to this second state). What's the proper way to accomplish this?
I am using dequeueReusableCellWith so I don't want to simply cycle through every cell because some that are out of sight probably shouldn't be modified. I simply want any cell that is visible, or becomes visible, while the table view cell is in this second display mode to follow a second design rather than the first design.
The second design, for now, is being modified via a method I added to a subclass of UITableViewCell like so:
- (void) p_refreshDisplay {
if (self.editing) {
self.buttonToClearWidth.constant = 20;
self.buttonToClearLeadingWidth.constant = 20;
} else {
self.buttonToClearWidth.constant = 0;
self.buttonToClearLeadingWidth.constant = 0;
}
}
However, I'm not sure how to trigger this p_refreshDisplay for every visible (and to become visible) cell. It seems unwise to call this many times and refresh the table view. What would be the proper way to accomplish what I want to do?
You do what should be done for any table view change:
Update your data model or some flag as needed.
Either call reloadData on the table view or call reloadRowsAtIndexPaths:withRowAnimation: passing in indexPathsForVisibleRows as the list of rows to reload.
Implement cellForRowAtIndexPath to provide appropriate cells for the given data/flags.
It sounds like you should have a custom cell class that has one or more properties that can be set on the cell in cellForRowAtIndexPath so the cell can render itself properly based on the specified state.
You can achieve this by doing three things:
Establish some property that indicates the "mode" of the table, either a boolean or perhaps an enum if there are more than three states
Ensure that cellForRowAtIndexPath configures the cell appropriately based on the value of this property. This will ensure that newly displayed cells are configured correctly.
When the "mode" changes you can use the tableview's visibleCells property to update any currently visible cells:
for cell in tableview.visibleCells {
if let myCell = cell as? MyCustomCellClass {
myCell.setButtonStyle()
}
}
I need an event, that changes a variable based on which TableViewCell I click. But unlike an action connected to a button, there is no action indicator for table view cells at all. So my question is:
I want to make a TableView that contains items of an array. Based on which item I click, I want to change my variable so that the result on the next ViewController depends on which button you click.
So to make things easier, here is an example what I want the app to look like:
On the first TableViewController I have a list based on an array and on the second ViewController I have a label that shows text based on the variable.
I have a nameArray = ["Mum", "Brother", "Me"] and a weightArray = [140, 160, 120] and a variable weight = 0. The label on the second ViewController tells the var weight. So when you click on "Mum" in the TableView I want the next ViewController to say 140, when I click on "Brother" then 160 and so on...
Until here everything works just fine and I have no problems with anything but changing the var based on what I click.
Long story, short sense:
I want an Action for the TableViewCell that changes the var like in an Action connected to a Button, but there is no Action outlet for Cells at all.
Use this method. Use indexPath.row to find what row number you selected
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var cell : UITableViewCell = tableView.cellForRowAtIndexPath(indexPath)!
switch cell.labelSubView.text as! String {
case "Mum":
self.weight = weightArray[0]
case "Brother"
self.weight = weightArray[1]
and so on..
..
default:
statements
}
}
Note A better alternative
I also considered a case where you have too many entries in nameArray and switch statement might not be good. In that case you can get the text inside the selected row by cell.labelSubView.text as! String
next you can check if the nameArray contains the cell text and get the index of the name that matches the cell text. Next you can get the required weight at the same index in weightArray. And then do self.weight = weightArray[requiredIndex]
Hope this helps.
Update : My experienced friend #Duncan mentioned down below that switch statement in this case is a bad coding practice . I am not going to delete it because it is a lesson for me and also my fellow programmers who are relatively new to programming. So i have put it in a yellow box, stating that it is not a good code
A better option for this would be :
As Duncan mentions, creating an array of dictionary is a good option
Second option is the option in my answer after my Note
You need to maintain array of dictionaries , those dictionaries have keys like "person", and "weight", then you can easily get weight value after selecting the cell by using table view delegate method UITableViewDelegate's tableView:didSelectRowAtIndexPath:
Create an instance variable in your view controller (a var at the top level after the class definition) for the selected cell.
class MyTableViewController: UIViewController
var selectedRow: Int
override func tableView(tableView: UITableView,
didSelectRowAtIndexPath indexPath: NSIndexPath)
{
selectedRow = indexPath.row
//invoke a segue if desired
performSegueWithIdentifier("someSegue");
}
override func prepareForSegue(segue: UIStoryboardSegue,
sender: AnyObject?)
{
if segue.identifier == "someSegue"
{
//Cast the destination view controller to the appropriate class
let destVC = DestVCClass(segue.destinationViewController)
destVC.selectedRow = selectedRow
}
}
As Andey says in his answer, it's probably better to create a single array of data objects (dictionaries, structs, or custom data objects). Then when the user taps a cell, instead of passing the index of the selected row to the next view controller, you could pass the whole data object to the destination view controller. Then the destination view controller could extract whatever data it needed. (Weight, in your example.)
Please don't mark this as a duplicate question because I have found no suitable answer for my query.
I have a table view with cells that contain text fields. I have a button at the bottom of the screen. The number of rows is greater than the screen can display, so some cells are not in view. I want that at any point when the button is pressed, all textfields be read and the text input be processed. I am unable to do so because apparently because of the reusability of cells, cells out of view do not exist at all and cellForRowAtIndexPath for those indexPaths gives a runtime error. I have read answers that say that this simply can't be done. But I find it hard to believe that there is no workaround to this. Please help. Thanks in advance!
This definitely can't shouldn't be done (accessing cells that are off screen, or implementing workarounds to allow it), for reasons of (at least) performance and memory usage.
Having said that there is, as you put it, a workaround. What you will need to do it change how you are storing the values in those text fields. Rather than iterating through cells and retrieving the text directly from the text fields you should store the text for each field in an collection.
Define a dictionary property on your table view controller / data source to hold the text for each row.
Act as the delegate of UITextField and assign as such in tableView:cellForRowAtIndexPath:
Implement textField:didEndEditing: (or whatever is appropriate for your use case) and store the text in the dictionary keyed against the index path relating to the cell that contains that text field.
Update the button action method to use this dictionary instead of iterating through cells.
Create a UITableViewCell subclass, add your tableViewCells a index property and introduce a delegate like:
protocol CustomCellDelegate {
func didEditTextField(test : String, atIndex : Int)
}
Create a delegate variable on your UITableViewCell subclass.
var delegate : CustomCellDelegate?
Implement the UITextViewDelegate in your tableViewCell and set the cell to be the delegate of your textfield.
Implement these two methods:
func textFieldShouldReturn(textField: UITextField) -> Bool {
textField.resignFirstResponder()
return true
}
func textFieldDidEndEditing(textField : UITextField) {
// call back with the delegate here
// delegate?.didEditTextField(textfield.text, atIndex: self.index)
}
So when the user ends editing the textField, your cell will call out with a delegate, sending the text and the index.
On your viewController, when you init your tableViewCell, set the delegate of the cell to the viewController, and set the index to indexPath.row .
Set up on your viewController a String array with as many items as many tableViewCells you got. Init the array with empty strings.
So you got the delegate on your viewController, and whenever it is called, you just insert the returned text to right index in the string array on your viewcontroller.
What do think, will this work?
If we can assume that cells that have NEVER been created has no text inputs, then create an Array or Set ourselves and clone the content/input texts there whenever user inputs to a cell's textfield.
Whenever, that button is clicked, you can iterate the array instead of cells to get all the inputs.
This is a bit hacky though..
I'm trying to do the opposite of what most people on this topic are asking to do. Most people want a button within a table view cell to call a method in their VC / VC table. I already have a protocol doing that.
Problem / Question
What I am trying to add now is the opposite: I need a button press on my main ViewController (which houses my table) to call a method within my CusomTableViewCell class (note: the button pressed on the main VC is not in the table). I have the protocol class created and the function written, but I don't know how to set the CustomCellViewClass as the delegate. When I did the opposite, I inserted "cell.delegate = self" into the cellForRowAtIndexPath method. I've also used prepareForSegue to assign a delegate. But with no segue and now cell-creation-method, I'm lost!
Example of Desired Function
My end goal is that pressing a button that is in the main VC will change the title of a button within the cells. A simple example would be that I have one view with a single table, on button press the table contents switch between two arrays, cars and motorcycles. When the table is showing cars, the cell button titles should all read "Look inside" but when showing the motorcycle button it should read "Look closer".
Code
I've already written the function that I want the cell to execute:
func cellButton_Title_Switch (currentList: String) {
if vcState == "cars" {
cellButton.setTitle("Look inside", forState: UIControlState.Normal)
}
else {
cellButton.setTitle("Look closer", forState: UIControlState.Normal)
}
}
I created the protocol:
protocol delegateToChangeCellBut {
func cellButton_Title_Switch (currentList: String)
}
I have the self.delegate.cellButton_Title_Switch(currentList) within my VC button and the protocol added to my custom cell class declaration. But how do I do that last missing piece in the custom cell class, where I assign the class to the delegate?
My original problem was that my UITableView's cell has buttons and labels, some of which change to match the state of things outside the table, things handled by the mainViewController.
The custom cell is defined by a customCellviewController. All the custom cell buttons and labels have their IBOutlets connected to the customCellviewController. I couldn't figure out how to make an action/change outside the table (in the mainViewController) immediately cause the cell labels and buttons to change.
Note: Protocols tend to work they other way around (a cell action triggers a function in the mainVC). I couldn't figure out how to use a protocol to solve this. Luckily, the solution was much simpler than a protocol.
The Solution!
I wrote the "updateCell" method that would change the labels and buttons and that code now sits in the customCellviewController. Then I called/triggered the "updateCell" function from the mainViewController simply by adding the call into my cellForRowAtIndexPath function. So it looks something like this:
var stateOfPage = "Green"
//Creates the individual cells. If the above function returns 3, this runs 3 times
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
//Setup variables
let cellIdentifier = "BasicCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! customCell
cell.updateCell(stateOfPage)
return cell
}
Now the above code/method runs when the table gets built. So to update the cells, have some button tap or other action reload the table data:
tableView.reloadData()
Good luck.