I'm trying to set up a view-based table in Swift using bindings. All of the examples I've seen use a datasource/delegate setup.
I have an array of Flag objects which has two properties - flagName: String and flagImage: NSImage. I have an NSArrayController managing this array.
If I set up a cell-based table, and bind one column to arrangedObjects.flagImage and the other to arrangedObjects.flagName, I get a table displaying images and names, and I can use the array controller's add and remove methods, so there are no problems with my datasource or my array controller.
I have been following the instructions in Apple's TableView Programming Guide to bind my view-based table to my array controller:
tableView Content binding: FlagController.arrangedObjects
textField Value binding: TableCellView.objectValue.flagName
imageView Value binding: TableCellView.objectValue.flagImage
(IBs autocomplete is not happy with the paths for objectValue.flagName respectively flagImage; it doesn't feel that there should be any completion whatsoever and says it can't resolve the path, so it looks as if the problem is with the tableView's content.)
If I do this, my table has a number of rows that corresponds to the number of elements that my array controller is managing at that moment (I have two simple setups, one object vs. 50 objects, so it's clear that something is bound). What I don't get is a display; and selecting a table row does not seem to send back a message to my flagController.
What am I missing? Has anyone been able to make this work? I've had no problems with other bindings in Swift so far, but I'm starting to think that the sudden reappearance of datasource examples is not unrelated to this.
It sounds like you've failed to implement the delegate method -tableView:viewForTableColumn:row:. That's a common cause of blank tables.
You don't actually have to implement that if you make sure the identifier of the table column and the identifier of the table cell view are the same in IB.
Otherwise, the method can just do this:
- (NSView*) tableView:(NSTableView*)tableView viewForTableColumn:(NSTableColumn*)tableColumn row:(NSInteger)row
{
return [tableView makeViewWithIdentifier:#"TheIdentifierOfYourTableCellView" owner:self];
}
(It could also do more, if desired.)
Related
I am drawing a tableview via BehaviorRelay.
Currently, I am using the code below as a way to add data.
viewModel.user.append(Person(name: "king", phoneNumber: "12341234"))
viewModel.personObservable.accept(viewModel.user)
I wonder if this code changes the user itself so that the whole tableView is redrawn.
If so, what method can I use to change only the data I added?
The code presented causes the personObservable (which is actually a BehaviorRelay apparently,) to emit a next event that contains an entire array of Person values, not just the latest Person added. Importantly, it's not emitting the viewModel.user object (at least not conceptually) but an entirely different object that happens to be equal to viewModel.user.
The default dataSource, the one that you get when you call items with anything other than a DataSource object, will call reloadData on the table view. This doesn't cause "the whole tableView" to be redrawn though, but it will cause the table view to query the data source for all of the visible cells, even if they haven't changed.
If you only want the table view to load the new cell, then the data source object needs to be smart enough to compare the new array with the array it's currently displaying so it can figure out which values are different and add/remove/move cells as appropriate, instead of just calling reloadData. As #Sweeper said in the comments, the RxDataSources library contains a set of data source classes that have that logic built in. If you wanted to reinvent the wheel, just write a class that conforms to both RxTableViewDataSourceType & UITableViewDataSource and implement the diffing yourself.
I have three elements in my UICollectionViewCell:
Two labels with name and price, and a quantity button.
I would like to add the name and the quantity with "didSelectItemAtIndexPath" to a specific collection view in the previous view controller and the price in another view controller. I may achieve this by using a segue to pass data to any view controller of my choice.
Also, at the same time, I want to keep track of the selections I make adding them to a table view below the collection view.
My guess is to create empty arrays for each item.. one for name, price and quantity.
I may be wrong.. and I tried to append my current selection and I know I am missing something.
To pass information to a previous viewController use a delegate protocol. Suppose a is your first viewController, and b is your second viewController.
You can create a delegate protocol in b (here you specify a func you want to execute inside of a)
Set a as the delegate for b
write a function yourDelegateFunction in a , which your delegate protocol will call to update the viewController with your first collection.
in didSelectItemAtIndexPath call delegate.yourDelegateFunction
Here's a video with an easy guide for how this works:
https://www.youtube.com/watch?v=3BcBu30thIA
If you provide a sample of your code, and highlight where you experienced issues, I can provide a more precise solution.
I am looking for some pointers on how to implement binding for a single click (similar to what NSTableView already has for Double Click on a row). Initially I thought, it is much simpler to leverage selectionIndexes property and make use of that. However when the table view gets loaded the value of this property corresponds to the zeroth index(first row) and it makes to think that the first row is always selected. Please note that I do not want to use the option of setting delegate/datasource for the tableview and use the available methods there.
I would like for each of the cells in UITableView be an entry field. In other words when the table appears and a user clicks/taps on a specific cell, the keyboard will appear and what ever the user types gets enter into the field. I will later use all these field as data in an array, for other uses.
Add a UITextField to each cell (design a .xib file for the cells and programmatically load the .xib as part of your table-view implementation). Implement UITextFieldDelegate, probably the textFieldShouldEndEditing: method because you might want to validate the input first and not let editing finish until the input is valid. In that method, if input is valid then store it in the array corresponding to what you were talking about. You'll need to do some tricks to find out what row you're currently validating, there's several ways to do it (one of which is shown here).
Edit 2: What I previously planned was probably a bad idea and I now changed my design: My UITableViewController has an array with all the values of my UITextFields and I am using delegation to update the values in the array. (If a value in one UITableViewCell changes, I send a message with the new value and the index of the cell).
Original Question
I would like to create a UITableViewCell subclass. To access my cells, I would like to have an NSMutableArray in my UITableViewController with all the cells. Whenever I create a new cell in - tableView:cellForRowAtIndexPath: I would add it to the array. The cells should however know about this array. I would declare a property like this for the UITableViewCell:
#property (nonatomic, assign) NSMutableArray *cellsArray;
Whenever I create a new cell, I would set its cellsArray to my array.
My (probably simple) question is: Is it correct that cellsArray will hold a pointer to the array in the UITableViewController and when I add stuff to the array of the UITableViewController, the cells will know this too, i.e. can access it?
Edit: The UITableViewCells contain UITextFields. I used to rely on the -cellForRowAtIndexPath: method and the visibleCells array, however when the cells moved out of view, the content of their UITextFields would also be lost. I then decided to store the cells in an array. When the user taps save, I iterate through the array and store the values. Also, I would like to automatically update the enabled property of the save button, depending on whether all cells contain something - for this I need all cells, too.
The cells should know about the other cells so that they can select the next cell when the return/next key on the keyboard is pressed.
If there are better approaches to this, I am glad to hear about them!
Not a direct answer of your question, but this sounds like a very bad design. Why should one cell need to know about its siblings? Any event/change that occurs in one cell and has an effect on the other cells should be handled by the table view controller. The single cells should be separate entities that should have no need to know about the state of each other.
Secondly, there is no need to introduce another array to manage the table cells. The table view already has a property visibleCells that you can access from the table view controller. And should never have to interact with invisible cells anyway because those are managed by the table view and its reuse facility.
I believe the answer is Yes.
My understanding of assign is that you can assign a value to such a variable and the retain count for the original object is not incremented. Similarly you need not release the variable in the object's dealloc method. You may run the risk, however, that the original array goes away and then cellsArray is pointing at something that is no longer there.
I use assign when I want to pass a reference to an object to another object (e.g. a view controller that is going to display or otherwise manipulate the object). And in the latter object, I do not release it's pointer to the object.
You also see assign used with properties that are id's, like
#property (nonatomic, assign) id<SomeProtocol> _myDelegate;
All that being said, with the exception of the id case, often I feel "safer" using retain for the property and being sure to release in dealloc. :-)
Anyway, I think that's the crux of the difference.