I have a property on my document class called passDescription, of type NSMutableDictionary. When I call setPassDescription:, the current value of the property is archived into an NSData instance using NSJSONSerialization. The property’s backing ivar, passDescription, is updated, and then an undo action is registered. The selector invoked by the action reconstitutes the NSData given to it and calls setPassDescription:.
Now, here’s the joker: passDescription is being observed using Key-Value Observing. Considerable experimentation and examination in Xcode’s debugger reveals that the old value and the new value are identical. (I know that this isn’t a pointer-aliasing issue, as that’s why I’m using an NSData instance. The NSData is created before I record the new value, making it independent of what it was created from.) Thus, when I press Command-Z to undo, nothing happens as the value that has just been restored is no different from the value that has been overwritten by the undo.
The only thing I can think of that may be causing this is that KVO is setting the passDescription ivar for me, before setPassDescription: gets called. Why would this be, and how could I prevent KVO from doing that? (I have confirmed that the setter isn’t being called twice. If it was, I would see double output in the debugger console.)
Here is the source for setPassDescription:.
- (void)setPassDescription:(NSDictionary *)param
{
NSLog(#"passDescription (before) = \n%#", passDescription);
NSError *error;
NSData *archivedOldValue = [NSJSONSerialization dataWithJSONObject:passDescription options:0 error:&error];
NSAssert(archivedOldValue != nil, #"Could not archive old pass description: %#", error);
NSData *blob = [NSJSONSerialization dataWithJSONObject:param options:NSJSONWritingPrettyPrinted error:&error];
if (blob == nil) #throw [NSException exceptionWithName:#"PBJSONException" reason:#"Could not serialize pass.json" userInfo:#{ #"error": error }];
[self.fileBrowserRoot fileWrapperWithName:#"pass.json"].fileContents = blob;
[passDescriptionLock lock];
[[self.undoManager prepareWithInvocationTarget:self] setPassDescriptionFromData:archivedOldValue];
passDescription = param;
[passDescriptionLock unlock];
NSLog(#"passDescription (after) = \n%#", passDescription);
// After the pass description has been set, refresh the list of build issues.
[self recheckForIssues];
}
Related
I added Book object in bookController (NSCreeController). Now i want to get stored Book object when i select the row.
- (IBAction)addClicked:(id)sender {
NSTimeInterval timeStamp = [[NSDate date] timeIntervalSince1970];
// NSTimeInterval is defined as double
NSUInteger indexArr[] = {0,0};
Book *obj = [[Book alloc] init];
NSString *dateString = [NSDateFormatter localizedStringFromDate:[NSDate date] dateStyle:NSDateFormatterNoStyle timeStyle:NSDateFormatterLongStyle];
obj.title = [NSString stringWithFormat:#"New %#",dateString];
obj.filename = [NSString stringWithFormat:#"%d",arc4random()%100000];
[self.booksController insertObject:obj atArrangedObjectIndexPath:[NSIndexPath indexPathWithIndexes:indexArr length:2]];
}
I concede there perhaps could be a better solution--
I am unfamiliar with how NSTreeController works, but I looked a the class reference and noticed that it has a content property, similar to an NSArrayController (Which I am familiar with grabbing specific objects from).
I believe that if the content property is actually of type of some kind of tree data structure, my answer here probably won't work. The class reference says this about content:
The value of this property can be an array of objects, or a
single root object. The default value is nil. This property is
observable using key-value observing.
So this is what I historically have done with the expected results:
NSString *predicateString = [NSString stringWithFormat:NEVER_TRANSLATE(#"(filename == %#) AND (title == %#)"), #"FILENAME_ARGUMENT_HERE", #"TITLE_ARGUMENT_HERE"];
NSArray *matchingObjects = [[self content] filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:predicateString]];
Then simply calling -objectAtIndex: will grab you your object. Note that the NSArray will be empty if the object doesn't exist, and if you have duplicate objects, there will be multiple objects in the array.
I also searched for an answer to your question, and found this SO thread:
Given model object, how to find index path in NSTreeController?
It looks pretty promising if my solution doesn't work, the author just steps through the tree and does an isEqual comparison.
If you could (if it's not too much trouble), leave a comment here to let me know what works for you, I'm actually curious :)
I have a basic NSTextView with rich text and graphics enabled (in IB). What I'd like to get is the path and filename of any images dragged in so I can pass those to another class.
I'm new to NSAttributedString but I've got a loop using enumerateAttributesInRange:options:usingBlock: looking for NSAttachmentAttributeName and that's all working fine. But going deeper, I get to the fileWrapper class and it's apparent inability to give me the path of the item.
How would I go about getting the name and path of the NSTextAttachment?
Related: Is there an easier way to get them all then stepping through the attributes?
Thanks much!
While I personally hold the design of NSFileWrapper in contempt, if you just need the data of each attachment you can access it as an NSData instance via NSFileWrapper's regularFileContents method. However, I needed a valid and explicit pathname to the attachment for my application. To get it is much more work than it should be:
You can subclass your NSTextView and override the NSDraggingDestination Protocol method draggingEntered: and you can traverse the NSPasteboardItem objects passed to your application during the dragging operation. I chose to keep the pathname and its inode number in an NSMutableDictionary, as NSFileWrapper can provide you with the inode of the referenced file. Later, when I access the NSTextView contents via an NSAttributedString, I can fetch the pathname of an attachment using the inode as an index.
- (NSDragOperation)draggingEntered:(id < NSDraggingInfo >)sender {
// get pasteboard from dragging operation
NSPasteboard *pasteboard = [sender draggingPasteboard];
NSArray *pasteboardItems = [pasteboard pasteboardItems];
for ( NSPasteboardItem *pasteboardItem in pasteboardItems ) {
// look for a file url type from the pasteboard item
NSString *draggedURLString = [pasteboardItem stringForType:#"public.file-url"];
if (draggedURLString != nil) {
NSURL *draggedURL = [NSURL URLWithString:draggedURLString];
NSString *draggedPath = [draggedURL path];
NSLog(#"pathname: %#", draggedPath);
// do something with the path
// get file attributes
NSDictionary *draggedAttributes = [[NSFileManager defaultManager] attributesOfItemAtPath:draggedPath error:nil];
if ( draggedAttributes == nil)
continue;
// the NSFileWrapper allows access to the absolute file via NSFileSystemFileNumber
// put the path and the inode (returned as an NSNumber) into a NSMutableDictionary
NSNumber *draggedInode = [draggedAttributes objectForKey:NSFileSystemFileNumber];
[draggedFiles setObject:draggedPath forKey:draggedInode];
}
}
return [super draggingEntered:sender];
}
One issue with my solution, that doesn't effect my application, is that multiple files dragged into the view (either singly or together) which are hard links to the same file, will only be indexed as the last pathname added to the dictionary which shares the inode. Depending on how the pathnames are utilized by your application this could be an issue.
i think i don't finish to understand all about memory and that stuff but this is my problem:
I have a variable defined idActual on a view that will be pushed (var defined in its header), i can read (NSLog(idActual)) and set it to nil without problems. BUT when i change its value i get an CFString error, that its supposed to be due to bad memory management, i've tried this:
i can do this: nextView.idActual = nil;
i cant do this:
a) nextView.idActual = #"1";
b) NSString *str = [NSString stringWithFormat:#"1"];
nextView.idActual = str;
c) NSString *str = [[NSString alloc] initWithFormat:#"1"];
nextView.idActual = str;
[str release];
a, b and c always give me the CFString error:
*** -[CFString isEqualToString:]: message sent to deallocated instance
It appears that the CFString (NSString) that is contained in nextView.idActual has already been released when you go to change the value. If you can post more of the related code, that would help.
I'm guessing that idActual is declared as #property(nonatomic,retain). When you try to set a new value into idActual, the setter method for that property is called (It's possible that the setter was automatically generated). The first thing that the setter method is doing is trying to compare the old value and the new value - and then it crashes.
When that setter method attempts to compare the new value to the old value, it runs into trouble because the old value is already deallocated.
Are you calling [nextView.idActual release] before you assign these new values ? If you are, comment out that line, and see if that fixes your problem. The auto-generated setter method will release the old value for you.
I have an NSMutableArray i am trying to convert into a string.
Declaring my NSMutableArray...
NSMutableArray *listData;
And later inside a method...
NSString *foo = [listData componentsJoinedByString:#"|"];
NSLog(#"%#",foo);
It seems no matter what i try i keep getting EXC_BAD_ACCESS.
To make sure each element in my array was an NSString i also tried this...
NSMutableArray *mArray = [[NSMutableArray alloc] init];
for (id ln in listData) {
NSString *boo = [NSString stringWithFormat: #"%#",ln];
[mArray addObject:boo];
}
NSString *foo = [mArray componentsJoinedByString:#"|"];
NSLog(#"%#",foo);
I can manipulate my NSMutableArray by adding/deleting objects in the same method or other methods inside my class. But when i try "componentsJoinedByString" the error pops up. Does anyone have any advice or another way i can combine this array into a single NSString?
In the code you've given, there will never be an NSMutableArray for listData. At some point in your code, you'll need to create one, and presumably populate it.
Edit
Okay, so you may get into memory management problems here, so let's be a bit clearer:
You're synthesizing getters and setters for the instance variable, so it's good practice to use those to access it, they'll take care of retain and releasing appropriately.
To set listData you can simply use
self.listData = [listManage getList:[[NSUserDefaults standardUserDefaults] stringForKey:#"list_name"] list:#"LIST"];
or
[self setListData:[listManage getList:[[NSUserDefaults standardUserDefaults] stringForKey:#"list_name"] list:#"LIST"]];
if you prefer.
I have a situation where I need to use some strings temporarily but I've read so many conflicting things that I'm a bit confused as to what the best way to proceed is.
I need to assign some strings inside an if structure but use them outside the if structure so they need to be created outside the if, I was thinking something like:
NSString *arbString = [[NSString alloc] init];
if(whatever)
{
arbString = #"Whatever"
}
else
{
arbString = #"SomethingElse"
}
myLabel.text = arbString;
[arbString release];
I have seen examples where people just used:
NSString *arbString;
to create the string variable
Google's Objective C guide says it's preferred to autorelease at creation time:
"When creating new temporary objects, autorelease them on the same line as you create them rather than a separate release later in the same method":
// AVOID (unless you have a compelling performance reason)
MyController* controller = [[MyController alloc] init];
// ... code here that might return ...
[controller release];
// BETTER
MyController* controller = [[[MyController alloc] init] autorelease];
So I have no idea, which is the best practice?
In the example you posted, you actually lose the reference to the NSString you created when you assign it in arbString = #"Whatever". You then release the string constant (which is unreleasable, by the way).
So there's a memory leak, since you never release the NSString you created.
Remember that all these types are pointers, so = only reassigns them.
As for the question, in this example, you don't need the [[NSString alloc] init]. You don't need to copy the string into a local variable anyway, you can just set myLabel.text to the string constant #"Whatever".
(edit: that's not to say that you can't use your pointer arbString, arbString = #"Whatever"; myLabel.text = arbString is fine. But this is just pointer assignment, not copying)
If you needed to manipulate the string before you returned it, you would create an NSMutableString, and either release or auto-release it. Personally, create autoreleased objects using class methods, so in this example, I'd use [NSString string], or [NSString stringWithString:], which return autoreleased objects.