OK, so I'm implementing a classic scenario :
A NSPopupButton with some items in it
When the selected value changes, my itemsArray is updated
The itemsArray is linked to an NSArrayController
Each item in the itemsArray is an NSMutableDictionary (with keys : title,content)
An NSTableView displays the titles of the arrangedObjects (binding)
An NSTextView displays the content of the selected item.
Now, what I want is to automatically save any changes to the itemsArray (or itemsArray's item title/content), but without using Core Data (which I suspect might have been the best way to go about it).
I imagine it's quite a basic question this one, but honestly I've never really like Cocoa's auto-magical way of doing things... so, I need your help...
How should I go about that?
You can write an array to a file very easily:
[yourArray writeToURL:someFileURL atomically:YES];
This will work if all the contents of the array are property list objects (i.e. they are NSNumber, NSString, NSDictionary, NSArray or NSData objects). This is the case in your example.
You can then recreate the array using either the arrayWithContentsOfURL: or initWithContentsOfURL: methods when you load from disk.
If your model object is more complex than just an array, then you should make your model object conform to the NSCoding protocol. This means you need to implement the initWithCoder: and encodeWithCoder: methods. You can then use the NSKeyedArchiver and NSKeyedUnarchiver classes to convert your object to and from an NSData representation that you can write to disk.
You should read the Archives and Serialization Programming Guide for more detailed information.
Another solution might be to add a Shared User Defaults Controller and bind the Controller Content Array from the Array Controller to the Shared User Defaults Controller
Related
I have a controller class that store a list of contact and I need to share this list to objects that will implement KVO on such array.
The most obvious solution is to use a NSArray instead of NSMutableArray, in order that everyone can use the same instance variable of the controller and it's not possible modify the content of the array.
Now, let's image that this list can change every 3 minutes and only the controller can update the content of the array.
If I dealloc and re-init the contact list array, all my KVO objects will lost the reference to my array.
Finally:
NSArray PRO: No one can alter the content of the array
NSArray CON: The controller can not modify the array without a dealloc, so other objects lost the reference.
NSMutableArray PRO: Controller can modify array content, all the object can easily share the same reference of the array
NSMutableArray CON: Everyone can modify the array.
Any suggestion?
NSArray in my opinion, given that it isn't being updated very often.
The object that owns and modifies the array exposes it through a property of type NSArray*. The observers observe this property. Whenever the object that owns the array recreates it, it sets the property to the new NSArray which then triggers KVO on all of the observers.
Alternatively, you can implement the indexed accessor patterns for the property.
I'm going through a simple Objective-C/Cocoa program to try and learn the language and am getting a little confused about how some things are linked from the code I write to the interface builder.
For example, I have a simple NSString:
#property (assign) NSString *letters;
And in my interface builder, I have a text field and I use the text field's bindings to connect it to letters.
However, the example also has this:
#property (assign) IBOutlet NSArrayController *wordsController;
In the view I have a table that continuously changes and shows different words and those words are stored in an NSMutableArray. I suppose I can understand that I just can't bind the array to the the table because there are some more complexities. So in the Interface Builder I create an Array Controller and bind it to the table. In the Array Controller's bindings, I bind the Array Controller to the array of words.
I understand that the last thing I have to do is also bind the Array Controller to my NSArrayController object as well. I don't understand why I do this through the main controller object by making a connection between this outlet and the wordsController. In the Array Controller's bindings section there's a greyed out option, Content Object, which says "An NSArrayController that the NSArrayController treats as its content." Why wouldn't I set the binding here? What is the significance of it being an outlet and why is it different than my NSString letters?
Thanks
You are confusing bindings and IBOutlets. This is not unreasonable -- it's a lot of Control-dragging of connections and it can be hard to keep clear what's going on. Let me try to explain:
Bindings are a way to let Cocoa handle the mechanics of keeping a model (some collection of data, even something as simple as a single NSString) and a view (an object which displays on the screen) in sync. When you "bind" your NSString to a text field's value, you are asking the framework to communicate changes to the string or the text field "behind the scenes"; your object which owns the string gets notified to change the string's value when the text field changes, and vice versa.*
A similar situation applies to your mutable array, array controller, and table view. You're essentially right about the complications: the mutable array and the table view don't know how to talk to each other; the array controller stands in between and facilitates: ("Okay, tableView wants to know what to put in row i. Array, give me your object at index i." :) In the past, you would've had to write that code manually, and it looked very similar every time you did so.
That's what the bindings do. They are a way to reduce boilerplate code. The IBOutlet to the array controller gives your object a way to send messages to the array controller, if necessary. One simple example of why you might need to do this is to allow a menu item to trigger a method in the array controller; a document object or another controller might handle the action from the menu item and call the appropriate message on the array controller. You can also ask the array controller for its arrangedObjects to get, for example, the sorted and filtered version of its content array.
* One side note here is that your NSString property should almost certainly use retain, not assign. The object that contains this variable should be responsible for its memory.
I tried to bind my NSArraycontroller to an NSMutableArray; the array holds objects of type "iData" (it's a custom class). The class further contains some NSMutableString variables which are set as keys for KVC. Then I bound the my NSTableColumn to the NSArrayController and set key model paths of every column respectively.
When I try to populate the array, the GUI does not show anything. What did I forget?
So it's likely that you solved this long ago, but in case someone else stumbles across this question...
I am populating the array via NSMutableArray, but I am not sure how can I populate the array via NSArrayController, since I don't have the instance in my Controller.m class. Please tell me how can I resolve this issue.
It is possible that you were doing something like
[myData addObject:someObject];
However, your NSArrayController will not learn of this change to the NSMutableArray instance because addObject is not KVC compliant. You need to inform any object that is observing that your NSMutableArray instance has changed. There are at least two ways to do this. Assuming that your NSMutableArray instance property is named "myData", then you can do something like the following:
[self.willChangeValueForKey:#"myData"];
[myData addObject:someObject];
[self.didChangeValueForKey:#"myData"];
or
NSMutableArray *bindingsCompliantArray = [self mutableArrayValueForKey:#"myData"];
[bindingsCompliantArray addObject:someObject];
Another SO answer (linked) has a good explanation on what mutableArrayValueForKey actually does, but I recommend reading the Apple developer docs on key-value coding and key-value observation to help understand it.
I have dragged the NSController instance in my mainmenu.nib tray. Do i need to declare an IBOutLet NSArrayController in my Controller.h file and then connect it with the NSArrayController instance in the tray ?
You need a NSArrayController instance in your nib file, but you do not need an IBOutlet in your interface for the situation that you've described here. The NSArrayController should be bound to the key of your NSMutableArray (myData in my example) and it sounds like you already have your table columns bound correctly.
Although Stephen's answer is probably "the way to go", I think the OP's original question "How do I insert/delete/manage my NSMutableArray using the NSArrayController, deserves a simpler and more direct answer:
NSArrayController provides a full and rich set of methods and even IBActions to fulfill almost anything you want on the managed NSMutableArray, with all the niceties of handling things "through filters", through selection, and "keeping sorting rules"
e.g. insert a new item so that it is inserted according to the current sort-descriptions.
Here's an excerpt from these methods (open NSArrayController.h for the full set) and remember that the 'content' is your NSMutableArray, while 'arrangedObjects' is an array provided by the NSArrayController that applies filtering and sorting to the content, "on its way" to the display in the NSTableView.
- (BOOL)addSelectedObjects:(NSArray *)objects;
- (BOOL)removeSelectedObjects:(NSArray *)objects;
- (IBAction)add:(nullable id)sender; // overridden to add a new object to the content objects and to the arranged objects
- (IBAction)remove:(nullable id)sender; // overridden to remove the selected objects
- (IBAction)insert:(nullable id)sender;
- (void)addObject:(id)object; // overridden to add to the content objects and to the arranged objects if all filters currently applied are matched
- (void)addObjects:(NSArray *)objects;
- (void)insertObject:(id)object atArrangedObjectIndex:(NSUInteger)index; // inserts into the content objects and the arranged objects (as specified by index in the arranged objects) - will raise an exception if the object does not match all filters currently applied
- (void)insertObjects:(NSArray *)objects atArrangedObjectIndexes:(NSIndexSet *)indexes;
- (void)removeObjectAtArrangedObjectIndex:(NSUInteger)index; // removes from the content objects and the arranged objects (as specified by index in the arranged objects)
- (void)removeObjectsAtArrangedObjectIndexes:(NSIndexSet *)indexes;
- (void)removeObject:(id)object; // removes from the content objects and the arranged objects (if currently contained)
- (void)removeObjects:(NSArray *)objects;
All this, of course, is for direct programmatic control over the content, and not "automagically" via Cocoa-Bindings.
I was able to save an NSMutableArray of custom objects to NSUserDefaults by implementing NSCoding in the custom class. However, now I want to save an NSMutableArray of these arrays. The compiler complains when I try to do this. How can this be done?
I found out how to do it. Basically, your transform the array into a data object using NSKeyedArchiver, and that is what you save with NSUserDefaults. Then when you get the data object back, you use NSKeyedUnarchiver to turn it back into an array.
I have a pretty standard setup where I have an array in my controller that I'm binding to an NSTableView. When I add an object to this array with the UI, I add elements by copying the array to a mutable array, adding the contents, then copying it back. I saw this idiom somewhere, but I'm not really sure where, or whether this is actually a sane thing to do. I t works fine on Snow Leopard, but it crashes really badly on Leopard. GDB tells me it happens right at the marked line, where I copy the new array back.
#interface MyAppDelegate : NSObject {
NSArray * urls;
//other declarations
}
#property (nonatomic, retain) NSArray *urls;
#implementation MyAppDelegate
#synthesize urls;
- (void)addThing:(id)sender {
NSMutableArray *newUrls = [NSMutableArray arrayWithArray: [self urls]];
[newUrls addObject: newurlimadding];
[self setUrls: [NSArray arrayWithArray: newUrl]];
}
I'm pretty sure I must be doing something boneheaded here. Is there a better way to do this? Why am I crashing?
NSMutableArray *newUrls = [NSMutableArray arrayWithArray: [self urls]];
[newUrls addObject: newurlimadding];
[self setUrls: [NSArray arrayWithArray: newUrl]];
What did you create newUrls for if not to set it as the new value of urls?
Besides that, there are a couple of things you're doing wrong:
No model objects. Bindings hates this. Unless your table view exists solely to display the different parts of the URL (scheme, host, path, etc.), each in one column, you're not giving Bindings what it wants.
Pay attention to the fields in the Bindings Inspector. Note that there are two: Controller Key and Model Key Path. They're exactly what they say on their tins: The Controller Key is the key for a property of the controller, which should provide model objects. The Model Key Path is the key path for one or more properties in the model, which usually should provide value objects, such as strings and numbers.
You probably need to create a model class and make the URL a property of that class. I'd guess that you have other objects, perhaps in parallel arrays, that you can move to properties of the model class. Do that, so that you're working with Bindings instead of against it.
Not using array accessors. You're just setting the whole array at once, which is inefficient and may cause display problems (such as selection highlights disappearing). Implement and use array accessors for this array property. Accessorizer can help you here.
I actually have no idea whether this will fix your crash because you haven't told us anything about it. You should edit your question to include any exception messages or other crash-describing output, which you'll find in the Run Log/Debugger Console.
Also, since the type of urls can be mutable, you should set it to copy, not retain.
NSArray * things; - since this can be modified you better represent using NSMutableArray instead NSArray.
When ever you need to add some new element to the list just use 'addObject' and insert element to the list.
Your binding will make sure that UI is updated using KVO and KVC.
It looks like the problem was that I had NSURLs as my object type. Once I changed the object in my array to a custom-made KVC compliant object, I wasn't getting any more crashes.
Maybe NSURL isn't KVC-compliant on 10.5, but it is on 10.6?