This isn't a "please help me debug my code" message. I actually have it working, but want a deeper understanding of how it works!
I have a view-based xCode application. On my main view, I have a UITableView and I've set the delegate and dataSource to File's Owner.
In my .h file for the Main ViewController, in the #interface section, I declare an NSMutableArray which will contain a list of custom objects.
In the #interface declaration, I include the protocols UITableViewDelegate and UITableViewDataSource.
Later, after a few button taps, my code parses an XML file from a server and inserts objects into the NSMutableArray. I added code to the cellForRowAtIndexPath function, which gets called as it should, and when I call the reloadData method for my UITableView, the table gets populated with the results parsed from my XML!
Pretty cool, but I'd like to understand how this happens; a better understanding will be useful to me in the future.
I never explicitly tie my NSMutableArray to that UITableView. Why does cellForRowAtIndexPath get invoked when an object is added to the array? How is it connected? Is it because the NSMutableArray is declared in the #interface block which has the protocols that I mentioned above? If I had two UITableViews on my .XIB how would the code know which NSMutableArray should be mapped to which UITableView? (Or is that something I should strive to avoid?) Even if I only have on UITableView on the XIB, if I have two NSMutableArrays, will I have to be concerned with them somehow tangling up my UITableView?
Thank you!
NSMutableArray --- in your case it is the data to be displayed in table view. When display has to happen Table view ask for the data using data source.
How they are connected -- Data source ask for the data there is not other explicit connection.
How to handle 2 table view -- Ideal approach is have different data source object for each table view, each object will have its own NSMutableArray of data.
1 table view and 2 NSMutableArray -- It is left to the data source implementation, depending on your need you can display data of any NSMutableArray objects.
Why does cellForRowAtIndexPath get invoked when an object is added to the array? -- you might be calling view reloadData
Whenever you call [tableView reloadData]; your cellForRowAtIndexPath method and numberOfRowsInSection are called.
Its because of the UITableViewDataSource protocol. There's no connection between NSMutableArray and UITableView.
When a new object is added to the array, after that [tableView reloadData]; will be called. Hence, now the cellForRowAtIndexPath method will be called for the array which will be having a count increased by 1.
Hope this wud help. :)
Related
I'm fairly new to obj-c and cocoa so please bear with me:
I have a NSTableView set up with cocoa bindings which works as expected with the simple -add -remove, etc methods provided by an instance of NSArrayController in my nib. I would like to programmatically add objects to the array that provides content for this controller (and hence for the table view) and then update the view accordingly.
I current have a working method for adding a new object to the array (verified by NSLog) but I can't figure out how to update the table view.
So: How do I update the bound tableview? (ie, after I have programmatically added objects to my array). I'm essentially after some view refreshing code like [view reloadData] in glue code, but I want it to work with the bindings I have in place.
Or is there a KVC/KVO related solution to this problem?
Code Details:
AppController.h
#interface AppController : NSObject
#property NSMutableArray *clientsArray;
-(IBAction)addClientFooFooey:(id)sender;
#end
AppController.m (note, I also have the appropriate init method not shown here)
#implementation AppController
...
-(IBAction)addClientFooFooey:(id)sender{
[self.clientsArray addObject:[[Client alloc] initWithFirstName: #"Foo" andLastName:#"Fooey"]];
//Need some code to update NSTableView here
}
#end
Client.h just simply defines two properties: firstName and lastName. The 2 columns of an NSTableView in my mainmenu.nib file are appropriately bound to these properties via an array controller bound to my AppController instance.
On a side note/as an alternative. How could I add functionality to the existing NSArrayController method -add, ie, something like: -addWithFirstName:andLastName and still have this compatible with bindings?
You have two main options for doing this provided your array controller is bound to clientsArray.
The first way is to just use the array controller's addObject: method instead of adding objects directly to clientsArray.
The other way is to keep your current addClientFooFooey: method but wrap your existing code with these two lines:
[self willChangeValueForKey:#"clientsArray"];
[self didChangeValueForKey#"clientsArray"];
This tells the KVO system that you are making a change to the array so it will go and look at it again.
The first option is the most straightforward, but if for some reason you need to update the array directly just let KVO know you are doing it.
I'm not sure if I am doing things right but this is my problem:
I have a view-based NSTableView using bindings to an arraycontroller.
I need to do some custom drawing on each row, depending the represented object as well as capture click in certain areas so for this I would need to have a controller for each row and set outlets for the sub-views in my custom cell view, but I don't understand how I can achieve this.
If I just add an object to the nib and make the connections to it, then I cannot tell which of the views is being drawn (or has been clicked).
You have to implement the delegate methods :
- (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
It's used by the table view to get a view for a give cell (column, row).
Then by using "makeViewWithIdentifier:owner:", you can get the a reusable cell with a given identifier and a given owner (view controller).
The simplest way is to design your cells in Interface Builder, and set a different identifier for each one. Then the method "makeViewWithIdentifier:owner" will automatically create a view for you for the given identifier.
I just found someone asked a similar question and the answer to it also satisfies my needs, so for anyone ending up here, this is what I did:
I set my NSTableCellView controller as the delegate of the NSTableView.
In my NSTableCellView subclass I implement the needed methods (drawRect:, mouseUp: and so forth) and call the respective methods in the controller.
To access the controller I get the NSTableView and then its delegate like this:
NSTableView *tableView = (NSTableView*)myView.superview.superview.superview;
MyControllerClass *controller = (MyControllerClass*)tableView.delegate;
[controller view:myView drawRect:dirtyRect]
On the controller, to tell which view is sending an event, I use their identifiers.
I have a UITableView that stores the selected row in User Defaults. The tableView is part of a menu structure that may be reloaded during the lifetime of the application, hence I want the persistence between loads. In viewDidLoad, this UserDefault is checked for existence, and I call
NSIndexPath *path = [NSIndexPath indexPathForRow:row inSection:0];
[self.tableView selectRowAtIndexPath:path animated:NO scrollPosition:(UITableViewScrollPositionMiddle)];
This works fine, as expected. However, it doesn't actually select the row, it just highlight's it. If I subsequently call
[self tableView:self.tableView didSelectRowAtIndexPath:path];
I get a crash - "unrecognised selector sent to instance". Why?
[self tableView:self.tableView didDeselectRowAtIndexPath:path] will call YOUR implementation of the deselection method (which is defined in UITableViewDelegate).
You get a crash since you didn't implement it in your delegate.
You should call:
[self.tableView deselectRowAtIndexPath:path animated:NO];
The UITableView works via two delegate protocols, UITableViewDelegate and UITableViewDataSource. The class that defines your UITableView should implement these protocols and you should set the delegate and datasource of the UITableView to "self". You should not call the protocol methods directly which is most likely the reason for your crash.
In order to select a particular row based on your data model (User Default), you will need to set the UITableViewCell selected property to "YES" in the tableView:cellForRowAtIndexPath: for the row that is being rendered.
I recommend going through this tutorial to help you understand UITableView's better.
http://www.iosdevnotes.com/2011/10/uitableview-tutorial/
My document based application has a window with a tableview. The tableview has a datasource which points to a class of type NSObject (called HopBill) which includes a NSMutableArray (aHopBill) and the needed tableview methods. So far so good.
For adding rows to the tableview I've added a sheet which is controlled from a NSWindowController (called HopBillSheetController). When pressing the OK button in the sheet. I actually need to do two IBActions (which is not possible): Add the row to the array of the tableview and close the sheet. I can connect the OK button in the sheet to the NSWindowController (to close the sheet) or connect it to the NSObject (to add the row to the array). But I want both :-)
Is it possible to call the IBAction in the NSWindowController from the NSObject? Or is there another way to do this?
I'm quite a beginner to Cocao and Objective-C, so please be gentle :-)
If your sheet is a nib/xib with an NSPanel, the call to close it is simply [panel close]; Assuming your window controller has a property for the panel, you can put the close code at the end of its row-adding IBAction. Or you could have the IBAction itself call another method if you prefer.
If your panel is running modal, you might need to stopModal too. (That's what's needed if everything stays frozen after the panel closes; otherwise never mind.)
Assuming hopBill, your data source, is a property of the window controller, any IBAction you write in the window controller also has access to hopBill; it can do everything you need.
So add a single IBAction to the window controller and connect the panel's OK button to it. That ought to work.
As for calling an IBAction from somewhere other than a control in a nib, yes, you can do that. Use a reference to the control as the sender arg, or nil if the IBAction doesn't use the sender arg.
You could also create your panel programmatically, or use NSAlert. But it sounds like your current setup is simpler -- and therefore better.
Take a look at this h file for an app controller: Apple's ClockControl example
The NSMutableArray *appointments property is the actual data source that will be used by the NSTableViewDataSource protocol methods. The IBAction "addAppointment" can access "appointments" directly: [self.appointments addObject:whatever atIndex:whatever];
The ClockControl example could be modified to use HopBill. You would import its declarations up top: #import "HopBill.h" And then instead of the "appointments" property, it would declare HopBill *hopBill; And "addApointment" would access HopBill's mutable array (aHopBill) like this: [self.hopBill.aHopBill addObject:whatever atIndex:whatever];
Why you can’t send messages to hopBill:
First, because although you declare it, you never initialize it. You have:
HopBill *hopBill;
[self.hopBill.aHopBill addObject: bHopAdditionAtInit];
It should be:
HopBill *hopBill = [[HopBill alloc] init];
[hopBill.aHopBill addObject: bHopAdditionAtInit]; // “self” won’t work here
Second, you’re declaring it inside an IBAction method, (doneHopBillSheet:), so it’s a local variable, accessible only within that method. If HopBill is holding your table’s data source cache, it should be a property of the controller which implements the NSTableViewDataSourceProtocol methods.
In your HopBill interface, you declare the aHopBill array to be a property, and you initialize it in HopBill’s init method (you should also release it in HopBill’s dealloc method). You need to do the same thing for the controller — it should have an instance of HopBill as a property, and that instance should be initialized in the controller’s init method.
If you want HopBillController to manage the tableview, its interface declaration should look like this:
#interface HopBillSheetController : NSWindowController <NSTableViewDelegate, NSTableViewDataSource> {
…
}
And, then, of course, you have to implement the relevant NSTableViewDelegate and NSTableViewDataSource methods.
Also, the controller must have an IBOutlet property for the tableview itself, and in the controller’s awakeFromNib method, it has to assign itself as delegate and datasource:
[self.tableview setDelegate:self];
[self.tableview setDataSource:self];
(The self-dot syntax assumes you’ve set up #property and #synthesize code for tableview.)
The IBAction method that adds items to your table must be in that controller class, or in a class that has a property which is an instance of the controller class. Then the IBAction method will have access to the aHopBill array and can add the new object to the array, after which it will call [tableView reloadData], which will in turn trigger the tableview protocol methods and update the table.
Now, that means that the xib containing the tableview has to have the controller as its file’s owner. Since you’re using NSDocument, I suspect that, instead, you would put the tableview outlet in the NSDocument subclass. And you would give that doc subclass a property which is an instance of the controller. The IBAction methods would also be in the doc subclass, and so they would have access to the controller and its HopBill property. Or maybe you would simply make the doc subclass the controller, rather than using the separate HopBillSheetController class. I’m not sure about the NSDocument stuff. But, remember, the IBAction method can itself call other methods, as long as it has access to instances of the classes in which those methods are declared.
Apple has an example using both the tableview delegate and datasource protocol methods. Go to this link and download the sample code: tableview example
It looks like a nice app. Good luck.
I'm just learning and playing with the apple Seismic XML example
http://developer.apple.com/library/ios/#samplecode/SeismicXML/Introduction/Intro.html
I've got most of it figured out, but the one area I can't get past is, if I want to remove the tableview controller and create a view controller populated with a tableview. I can get the tableview to appear fine, but no matter what I try I can never get it to populate.
In the viewdidload area I can setup the tableview, color the background, do whatever I want to do, but I seem to 'lose' control of it somehow.
In short, would someone please be able to give me the steps involved in correctly changing the tableviewcontroller to a viewcontroller with a tableview in the apple example?
Thank you.
Lian, you need to read the documentation on UITableViewController. http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/TableView_iPhone/AboutTableViewsiPhone/AboutTableViewsiPhone.html
I'm not sure what you mean by "remove the tableview controller and create a view controller populated with a tableview" or why you would want this configuration. If you're having trouble with populating the tableViewController, you just pass in the data, usually from an NSArray or NSDictionary in the cellForRowAtIndexPath method. You either need to select the UITableViewController template when you create the class file or include the UITableViewDataSource and UITableViewDelegate if you're adding a tableView to a ViewController.
If you mean you want to change the view controller on screen, then you're looking to pop to another view using the navigation controller.