Noob warning!
My app displays data in a standard NSTableView via NSArrayController all via bindings. All cool.
There is a filterPredicate, “completed tasks” which is toggled by a check box which drives a BOOL in the background. This works great when the app is running, filter on, filter off, but if I set the BOOL to NO in either init or awakeFromNib, the NSArrayContoller ignores the filterPredicate, but works later.
I could use the predicate to deliver a filtered array to the AC, but guessed bindings & direct filterPredicate would be better.
The AC is init’d in the NIB file and from looking at the KVO feedback, gets created very early on. The filterPredicate does not exist when the AppController inits, but does by the time we get to awakeFromNIb.
Any ideas what I am missing?
Edit:
This is the method called by the check box action:
- (void)displayClosedJobs {
if (self.showClosedJobs)
{
self.showClosedPredicate=nil;
}
else
{
NSString *predValue=#"Closed";
self.showClosedPredicate=[NSPredicate predicateWithFormat:#"!(DisplayName contains[c] %#)",predValue];
}
[self changeTableSortOrder];}
This is also called on init and awakeFromNib.
Most likely you set the bool variable in your init/awakeFromNib directly like so:
_myBoolVariable = NO;
However, what you have to do to send the correct KVO notifications for bindings to notice the change, is use the setter method explicitly either by
[self setMyBoolVariable:NO];
or by
self.myBoolVariable = NO;
However, it's hard to tell without seeing your initialization code. If this is not the problem you should provide more details about how you initialize the variables and how your bindings are set up.
Related
I'm getting some weird behavior, I Set a Label in Interface Builder, then I connect the label to a file as an Referencing Outlet.
#property (weak) IBOutlet NSTextField *TitleLabel;
When I access that label in the file (cell.TitleLabel.stringValue = title) and run the application, it doesn't recognize it.I get this:
-[NSApplication TitleLabel]: unrecognized selector sent to instance 0x608000101680
The weird thing is that it doesn't always do this, sometimes it works and displays correctly, other times it doesn't.
I've just started messing with IB so I'm probably missing something. Any help?
Is the property really on your NSApplication subclass? or is it on you application delegate class? It's not impossible for it to be on the application object, but it would be a pretty uncommon (and arguably ill-advised) pattern.
In short, I suspect you're probably connecting it to the wrong object.
EDIT: Ah. I see. You're trying to access things via the topLevelObjects array, but in practice, you can't count on the order of topLevelObjects. What you need to rely on the owner's outlets getting populated, but you're passing nil for the owner. topLevelObjects only exists to give the caller "ownership" (in the reference counting sense) of the top level objects in the xib for memory-mangement purposes, it's not really meant to be "used" directly like you're doing here. (In fairness, I can imagine situations where you might need to introspect that array, but this hardly rises to that level.)
The canonical way to do this would be to use an NSViewController subclass as the owner. In Xcode, if you add a subclass of NSViewController to your project, it will give you the option to create a xib file at the same time that will have everything hooked up. Then you just initialize the NSViewController subclass at runtime and the view outlet property of that class will be filled with the root view. You can obviously add more outlets and plug in whatever you like.
This post appears to cover the basics, if your looking for more details. Apple's docs on xib files and how they work are here.
The problem was that the View would sometimes get assigned to NSApplication. I'm not sure if the way that I am initiating the view is the common way of doing it but the problem was within this block of code:
NSArray * views;
[[NSBundle mainBundle] loadNibNamed:#"CollapseClickViewController" owner:nil topLevelObjects:&views];
CollapseClickCell * cell = [[CollapseClickCell alloc] initWithFrame:CGRectMake(0,0,320,50)];
cell = [views objectAtIndex:0];
the problem was that [views objectAtIndex:0] would sometimes return NSApplication. To fix it I just checked the class against itself and returned that object via:
-(CollapseClickCell*)assignCell:(CollapseClickCell*)cell withArray:(NSArray*)array{
for ( int i = 0; i< [array count]; i++) {
if ([[array objectAtIndex:i] class] == [CollapseClickCell class]) {
return [array objectAtIndex:i];
}
}
return nil;
}
I then assign that to the object:
cell = [cell assignCell:cell withArray:views];
It may not be the conventional way of doing it but it works. If there is a better technique or a more common approach please enlighten me! :)
I have a UITableView with a property(strong, nonatomic)NSMutableArray *currentContent, I also have a property(strong, nonatomic)NSMutableArray *cellHeights to keep track of the cell heights cos the user could expand or collapse each cell. The self.currentContent is set by another controller which load data from a web service, so it will change as the data load, I want to keep both of these variables in sync. As soon as currentContent is updated, I want to update cellHeights. How do I do that?
I tried:
- (void)setCurrentContent:(NSMutableArray *)currentContent{
_currentContent = currentContent;
self.cellHeights = [NSMutableArray arrayWithDefaultHeightsForCellCount:[currentContent count]];
}
But it's not working, cos it will only be set at the first time when I set currentContent, when it's empty. So self.cellHeights currently will stay empty. When there is finally value in self.currentContent, self.cellHeights was not updated.
I've done a similar thing before, with variable cell heights depending on the content from your web-service, and I'd advise that keeping an array of cell heights might not be the best idea.
What I did was to create a 'fake' cell in the viewDidLoad: method, that I use just to calculate cell heights.
Then I use the 'heightForRowAtIndexPath' method to specify how tall cell should be by populating the 'fake' cell with the data for the index path, then finding out how tall that cell is. For example:
#interface MyTableViewController()
#property (nonatomic, strong ) MyCustomTableViewCell *cellForTestingHeight;
#end
#implementation MyTableViewController
- (void)viewDidLoad {
[super viewDidLoad]
self.cellForTestingHeight = [[MyCustomTableViewCell alloc] initWithStyle:UITableViewCellStyleDefault];
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
NSDictionary *myData = [self.data objectAtIndex:indexPath.row];
self.cellForTestingHeight.viewData = myData;
return self.cellForTestingHeight.height;
}
#end
This code assumes that you've created a class called MyCustomTableViewCell which has a method to set the viewData property on it, and that after setting that property you'll be able to tell how tall that cell will be by accessing a height property.
What you need to do is observe changes to the mutable array itself, not your property which references the array. This should be straightforward but unfortunately there is a twist...
OK, let's assume there is no twist and rather than an NSMutableArray your property is of type MyObservableClass. Then to setup the observing you would do something like this (all code is pseudo - i.e. typed into the answer):
- (void)setCurrentContent:(MyObservableClass *)currentContent
{
if(_currentContent)
[_currentContent removeObserver:self forKeyPath:#"myObservableProperty"];
_currentContent = currentContent;
[_currentContent addObserver:self forKeyPath:#"myObservableProperty" ...];
}
Now whenever the currentContent is changed your code stops observing the properties of its old value and starts observing properties of its new value.
Easy, but its not quite that simple for arrays...
The twist, though KVO will inform an observer of additions, deletions and changes to a collection the NSMutableArray class doesn't issue those notifications. You need to use a proxy for the array, and such a proxy is provided by the frameworks - see for example NSArrayController and mutableArrayValueForKey:. However the second part of the twist is that the changes to the array must be done through this proxy - you can't have your client call setCurrentContent and pass any NSMutableArray if you are going to observe it, your client needs to pass in the proxy... Whether you can use this easily in your design you'll have to figure out. You'll need to read Automatic Change Notification in this document and other Apple docs to sort this out.
This sounds more complicated that it needs to be, maybe somebody else will provide a more succinct way of doing this.
I am working on a project in which I perform lazy loading of images. When the imagedownloader downloads the images,it sends the message to its delegate to handle the image. But when its delegate,which is a view controller, gets deallocated from memory,I dont want imagedownloader class to send messages to its delegate as its already dead. I need to know when can i set delegate of imagedownloader to nil?? My target is set to iOS4.0 so i cant use weak references. And i have many instances of imagedownloader stored in a dictionary ready to sent their delegate the completion message . I have to set delegte of all those stored instances to nil.For now i am doing
'
-(void)viewWillDisappear:(BOOL)animated
{
for(imagedownloader *imagedownloaderObj in dict)
{
imagedownloaderObj.delegate = nil;
}
[super viewWillDisAppear:animated]
}
but it crashes in the loop. Please help anyone...and sorry about my bad english but i hope you got it whats my problem..
You have a problem in your code - you are enumerating a dictionary which enumerates its keys, not its objects. Instead you want to do:
for(ImageDownloader *imageDownloader in [imageDownloaderDictionary allValues])
{
if (imageDownloader.delegate == self)
imageDownloader.delegate = nil;
} //note - I've adjusted naming to match Objective-C style conventions. It fits in better with the framework code now.
Also, I'd say to do this in dealloc instead. I don't know that you'll always get a viewWillDisappear: method before deallocating, on earlier version of iOS (including iOS4) you certainly couldn't guarantee that. And furthermore you don't want to waste time downloading the images again if you come back to that view.
I currently have a class with 15 properties (and growing), and I'm finding myself having to call an update method every time one of those properties change.
Currently, I'm overriding every setter with a code like this:
-(void)setParameterName:(NSUInteger)newValue {
if (_param == newValue)
return;
_param = newValue;
[self redraw];
}
The method [self redraw]; being the key here.
Is there a better way to do it? Should I be using keyValue observers (the method observeValue:forKeyPath:ofObject:change:context:)?
Notes:
All properties (so far) are assign (mostly enum, NSUInteger, CGFloat and BOOL);
All those properties are set using bindings (method bind:toObject:withKeyPath:options:). Except when loading from the filesystem (which is not important, as I already call the drawing methods on every object after the loading is done);
The value changes are only for the current object. I do not need to be told when changes occur on other objects;
I have other properties that I don't need to watch the changes on it (because it will have no effect on my output and drawing the output is kinda time-consuming).
Thanks!
Since these properties are updated using bindings, which invoke -setValue:forKey:, you can override that method instead of writing custom setters:
+ (NSArray *) keysAffectingDrawing {
static NSArray *singleton;
if (!singleton)
singleton = [NSArray arrayWithObjects:
#"property1",
#"property2",
#"property3",
nil];
return singleton;
}
- (void) setValue:(id) value forKey:(NSString *) key {
[super setValue:value forKey:key];
if ([[CustomClass keysAffectingDrawing] containsObject:key]) [self redraw];
}
(I was first inclined recommend key-value observing but agree it's not the best solution here. I think the reason is in part that there's only one object, and in part because the design doesn't follow MVC. Usually in MVC an object that draws itself isn't the one with all the properties.)
(Added: Ahh, I see. The model is responsible for rendering the properties to a bitmap, and that's what -redraw does. That's fine MVC. To make it clearer, I recommend changing the name of the method from -redraw to something like -updateImage or -renderImage, since it doesn't actually do any drawing.)
You could use the Key-Value Observing to avoid repeating in all properties setter the method call, however i think that calling the method directly in the setter is not the wrong way to do it, and could even be faster ...
I have an NSComboBox in my mainmenunib file.
I have created an outlet of combobox "cb" and made a connection of it with my delegate
I also connected delegate and datasource with my delegate.
-(void)applicationDidFinishLaunching:(NSNotification *)aNotification
{ arr=[NSMutableArray arrayWithObjects:#"a",#"b",#"c",#"d",#"e",#"f", nil];
[cb reloadData];
}
-(NSInteger)numberOfItemsInComboBox:(NSComboBox *)aComboBox{
return arr.count;
}
-(id)comboBox:(NSComboBox *)aComboBox objectValueForItemAtIndex:(NSInteger)loc{
return [arr objectAtIndex:loc];
}
But when I run the application data is not coming in combobox.
Please help me out as i am new to cocoa programming.
Thanks in advance.
Your approach seems reasonable on the face of it, though using a mutable object as an instance variable is often ill-advised (for reasons wholly unrelated to your issue here, and which we needn't get into at this stage).
There are two things that jump out as possible issues:
1) Are you using ARC? If not, arr is going to disappear from under you because -arrayWithObjects returns an autoreleased object and you have nothing retaining it. If you are using ARC (the default for new project on Lion, I believe), this doesn't apply to you. Plus I would expect you would crash, not just get no data.
2) More likely, you forgot to -setUsesDataSource:YES, which is the flag that tells NSComboBox whether to look at its data source or to use the internal contents approach that #JustinBoo supplied. I believe this defaults to NO, which would cause your exact problem. I don't have Interface Builder in front of me at the moment, but IIRC there is a "uses data source" checkbox that you can check to enable this attribute.
You can add objects using -addItemWithObjectValue to Your NSComboBox like this:
arr = [NSMutableArray arrayWithObjects:#"a",#"b",#"c",#"d",#"e",#"f", nil];
for (int i = 0; i < [arr count]; ++i)
{
[cb addItemWithObjectValue:[arr objectAtIndex:i]];
}
You can see NSComboBox Reference for more information.