I need to instantiate some properties with the content of the saved document. Since theses properties are used by my interface, I would like to instantiate them before the NIB is loaded.
At which point of my initialization can I access the data of the loaded document ?
If possible, I would like to access it not from the initFromURL method. Indeed, when I create a document, I also create this data. So, if it is possible, I would like to put the instanciation at only one point, that will work for both the creation and the opening of a document.
So, is there an accessible point after the initFromURL and initWithType methods but before the windowControllerDidLoadNib.
Thanks !
Easy !
-windowControllerWillLoadNib
Related
I have a class that reads from a DB on startup. I'd prefer to be able to store it in the session, but I get the following error when trying to do so:
ERROR TypeError: no marshal_dump is defined for class Mutex
Is what I'm doing possible/reasonable? If so how should I go about doing it? If not, whats a good alternative to storing the class instance in the session? Currently my workaround is just instantiating it whenever I need to use it, but that doesn't strike me as a good solution or one that will be able to scale.
A good alternative is to store the id of the record in the session. Then when you need that data again you'd use a helper to return the data either from memory or from the database. A perfect example is the pattern used in current_user helper methods found in many ruby authentication gems. You could modify this helper to use a cache layer if you find it to be a bottleneck, but I'd leave that as an optimization after the fact.
Issues of having to get the object into a marshaled format that will live happily in a session, there are issues with storage space, stale data and possibly unintentional exposure to confidential data.
Is it possible to manually create WebDataSource objects and then set the created object to be the datasource of a webFrame object? I can't seem to find a method on WebFrame class that allows the setting of datasource. The goal is to asynchronously pre-load webpages without having to render them in a web view all at once.
Just use an offscreen WebView. It'll load the resources for you and not waste time drawing itself.
(I gather this is a follow-up to the question I answered a little while ago?)
As I alluded to in my comment on that question, you use one of the -[WebFrame load...] methods to load content. When you issue the load request the WebView instantiates a -provisionalDataSource which in turn becomes the -dataSource (so much for clear naming!). As the class documentation summarizes:
The provisional data source transitions to a committed data source
once any data is received.
Unless you are extending WebKit, I don't think there is usually a reason to create WebDataSource instances directly. Let WebFrame do it for you.
I have a document based application. I have overridden dataOfType function to save the appliation. However I am unable to retrieve the application name given by user in NSSavePanel while saving. Is there a way I can get the application name. Also which function is invoked after dataOfType is invoked which can be overridden
Why do you want this information? Apples documentation says you shouldn’t try to access the name or file URL in dataOfType: or any of the other saving methods, since this is old information. Also cocoa might request your document object to save itself at some temporary location and not to the real path.
If you really want that information though you’d have to override one of the lower-level save methods. The exact order in which they get called is documented.
My document-based Cocoa application uses a NSOutlineView/NSTreeController combo, bound to the document's Core Data store. My NSTreeController has the fetch predicate isRoot == YES. isRoot is a transient boolean attribute with a default value of NO. My root model's awakeFromInsert calls:
[self setIsRoot:[NSNumber numberWithBool:YES]];
I'm able to add objects to the hierarchy just fine, but when I try to load a document I just saved, I get an exception:
[<NSDictionaryMapNode 0x1001a8190> valueForUndefinedKey:]: this class is not key value coding-compliant for the key isRoot.
I can work around this exception and successfully load a newly-saved document if I change the isRoot attribute to non-transient in the xcdatamodel, but based on my understanding of the transient flag it should not cause a problem, and this really isn't the kind of data that should be persisted.
I have also tried implementing -isRoot in the NSManagedObject subclasses to return the appropriate fixed value, as well as making the same setIsRoot: call within awakeFromFetch, both to no avail.
Is there some other subtlety I'm missing? I can't imagine that fetch predicates don't support transient attributes. I don't know much about the inner workings of Core Data but it seems interesting that it's trying to look up isRoot on the store-specific class and not my NSManagedObject subclass.
I can't imagine that fetch predicates
don't support transient attributes.
After a bit of research, I can tell you that they don't. See this document. Quote:
You cannot fetch using a predicate
based on transient properties
(although you can use transient
properties to filter in memory
yourself).
I've put together a test project and can verify I get exactly the same error as you do.
When I need to filter out the root nodes in a tree, I use a fetch predicate of parent == nil instead of a transient attribute.
I understand your reaction - I too wanted way of having an attribute specifically called isRoot too. My guess is it's possible, but it'd take so much code it's just not worth the hassle.
Oh, and if you're dealing with core data any more than a little, mogenerator will make your life much easier.
Another option is to have a separate class for the top-level nodes, use that class name as "Entity Name" and leave "Fetch Predicate" blank. As long as the child nodes have the same values as the top-level node (I use a common superclass/entity inheritance), everything still works.
Have you made sure that the NSTreeController is set to control an entity rather than a class?
From your error, it looks like it might be set to a class with the default - NSMutableDictionary.
I'd also argue that maybe isRoot could be persisted. It depends on what you're trying to do with your app, of course, but if it's a tree view that gets loaded on app run I'd either make isRoot persist.
Ok, I am creating a document-based application in Cocoa and the document's file type is actually a package. Within that package is an XML settings file, a SQLite database and a zip file which is downloaded at runtime. Now the only thing that changes, really, is the XML settings file as the other ones can be recreated at run-time.
Each one of these packages will have one and only one window, hence my desire to use document-based. These files can also be copied, renamed, moved, etc. just like any other file that is part of such an architecture.
But I am completely lost as how to implement this in the Documentation Framework! It seems everywhere I look in the docs it's always talking about in-memory representations of the files which you then write out using the path presented to you in one of the NSDocument overrides (since Cocoa may move it, etc.) But again, I'm using a SQLite database that sits on disk, not in memory.
I have looked all over for overridable methods that would still give me things like dirty-state checking of the doc, open and save file dialog support and the like, but I can't seem to find anything that just says 'Here's a file URL... Open it as you see fit' althought I did get close at the application's delegate level, at least for the opening.
So let's assume that's working as expected. How do I implement the save/save-as where I want to control everything that is written to disk or not? I don't want to (not can I) mess around with data structures or the like. I just want to be given a psth that the user selects in the 'Save As' dialog (for new) and be able to write what I need to there. Simple. But again, the 50+ page document from developer.apple.com about Document-based architecture tells me where to overload a lot of things, but every one seems to stem from some in-memory representation of the document, which again, is not what my package is. Technically, only the internal XML file is what would be tied to the document. Everything else is just support for it.
So? Anyone? Takers?
Mark
I can't seem to find anything that just says 'Here's a file URL... Open it as you see fit'
Implement the readFromURL:ofType:error: method in your document class. Alternatively, since your document type is a package type, implement the readFromFileWrapper:ofType:error: method.
You don't have to read the data into memory; you can do whatever you want in whichever method you implement, including opening the database.
How do I implement the save/save-as where I want to control everything that is written to disk or not?
Implement the writeToURL:ofType:error: method or the fileWrapperOfType:error: method.
If you had or could easily create data in memory, you would implement the readFromData:ofType:error: and dataOfType:error: methods. The URL-based and file-wrapper-based methods are for cases where data in memory is not an option. And the primary use of file wrappers is for package types like yours.
Actually, I found it. It's not the 'writeTo' methods, but rather the 'saveTo' methods you want to override. When I did that, the saving code worked as I expected, including automatic save panel support. For clarity, this is the one I chose...
saveToURL:ofType:forSaveOperation:error:
and it works like a champ! Not too confusing now, was it! Sheesh!!!
That was of course the very first thing that I tried, but if you read the developer documentation--specifically the Cocoa Document-Based Architecture--here's what it says about those very methods...
During writing, your document may be asked to write its contents to a different location or using a different file type. Again, your overridden method should be able to determine everything it needs to do the writing from the passed-in parameters.
If your override cannot determine all of the information it needs from the passed-in parameters, consider overriding another method. For example, if you see the need to invoke fileURL from within an override of readFromData:ofType:error:, perhaps you should instead override readFromURL:ofType:error:. For another example, if you see the need to invoke fileURL from within an override of writeToURL:ofType:error:, perhaps you should instead override writeToURL:ofType:forSaveOperation:originalContentsURL:error:.
In other words, it seems to say that you can't assume the URL that is passed to you is the actual place on disk where the 'something' is eventually written to, which wreaks havoc when dealing with database files that are opened by URL. Maybe I'm missing something.
But ok... forget I read that and simply even try to just override those methods. I do and return TRUE for each, (I log the URL so I can see what is being passed in), I get this error on 'Save As' after you have chosen a filename...
2009-10-28 14:31:51.548 XPanel[1001:a0f] dataOfType:error: is a subclass responsibility but has not been overridden.
...but when you look at the documentation for that it says the default implementation throws an exception because you must override one of the other implementations above... which I obviously just did! Plus, again, this can't be represented as simple data!
So grasping at straws here, I overrode that one too and just returned nil, since again, you can't represent what I'm doing with a NSData object. Then I get a 'Can't be saved' message.
WTF?! Why is it calling that thing anyway??!!
...and that's when I gave up and posted this here.
Now if YOU can give me a simple example that perhaps doesn't even actually read or write a file but instead just logs the URL, that would be perfect. Not to useful but still, it should work... I just can't seem to implement get it to.