I'm new to Core Data and I can't find the answer into the docs (but I'm sure it's somewhere):
I defined the properties for my entities and test my third version of an application (ASOC, ObjC, ObjC+CoreData): I write, read, create and remove objects, undo/redo actions, autosave, and everything is working like a charm for the moment (Stefan, my old dictionaries are gone and replaced by… well… managed objects I suppose )
I'm saving my file in binary format. The images, icons, rtfd texts are"Transformed"-type properties, because binding images by data is a deprecated manner which issues a warning (once).
Now: what if I decide to ADD a property to an entity? The previous files become unreadable! The app issues an alert:
The document “xxx” could not be opened. The file isn’t in the correct
format
I suppose Apple has implemented a sort of "backward compatibility", as the file is archived with keys/properties: when I archived some dictionaries, I could add or remove keys without problems…
Any link welcome!
If i understood you right, you changed your Core Data Model and want to use it with the binary store you used before. If it's the issue, you need to make a Core Data Migration, the whole process of which is described here.
http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/CoreDataVersioning/Articles/Introduction.html
Related
I have a second .nib file that is a localized version of the main one in my Cocoa project.
I want to be able to perform some kind of 'update', as in, if I want to add new elements to the original, I want to be able to update it to the localized one. A solution can be deleting and re creating the localization, however the problem that I am facing is that if I have elements which I have changed from the second nib file (e.g. increase size of a label), this is then lost.
How can I do this 'update'?
Thanks
I use the free Localization Suite for managing localizations of my app. It can synchronize changes in your main localization into the other localized NIBs/XIBs, without breaking layout/sizing adjustments you've made in the localized version. It handles the whole localization process pretty well. There are other tools and approaches to this problem, but this is the one I like.
For a completely different approach, see Wil Shipley's blog post on the subject. The flaw in his approach is that it doesn't adjust sizing for localized versions. He addresses this by always making UI elements wide enough to fit the longest localization.
I'd like to store some additional information along with a document, but I can't use bundles or packages, and I cannot store it inside the document itself.
The application is a text editor, and I'd like it to store code folding and bookmark locations with the document, but obviously this cannot be embedded into the code directly, and I don't want to alter the code with ugly comments.
Can I use NSDocument to store information in the resource fork of a document? If so, how can I do this? Should I directly write to <filename>/..namedfork/rsrc or is there an API available?
First, don't use the resource fork. It's virtually deprecated. Instead, use extended attributes. They can be set programmatically at the BSD level via setxattr and getxattr. Extended attributes are used in many places... for example, in the latest OS X, the resource fork itself is implemented as a special type of extended attributes.
For example, the Cocoa text system automatically adds an extended attribute to a file to specify the encoding.
I thought NSFileManager and NSFileWrapper supported extended attributes since Snow Leopard, but I can't find any documentation :p You can always use the BSD level functions, though.
Does the state need to move with the file if it's copied to another computer? If not, you could do a lot worse than emulating the way Bare Bones handles document state with BBEdit. They store state for all documents in ~/Library/Preferences/com.barebones.bbedit.PreferenceData/Document State.plist.
The resource fork documentation is here. But it contains plenty of suggestions to not use the resource fork.
I have a class on my web site for reading and writing resource forks, which I have never got around to moving to my GitHub repository because, as Yuji points out, they are not really used any more.
I was going to say alias files and web Internet location file are the only places they are used, but I used and tested it on Mac OS X v10.7 (Lion), and they are not even used there any more; they may still be used for custom icons. I didn't test for that exclusively. I will have to see how that affect my NDAlias class on 10.7.
ndresourcefork
I resort to your expertly advice because I am sort of "new" to Objective-C, I have read a couple of books and docs (namely Aaron Hillegass & Stephen G. Kochan's books), but some things are still unclear to me, for lack of practise.
To put you in context, I have a NSDocument project that uses Core Data for storage.
I struggle with 2 things right now: reading/writing to files, and table views ^^
So my first question is about Core Data : is it only able to save in SQL, XML or Binary format ?
Or can I use core data to read/write in any format, according to what I declared in the plist file ?
I am trying to work with .po files, and I want to display the translations in a table view containing 2 columns (1 for the msgid and the other for the msgstr).
To read and write files in the po format and display lines in my table view, I most likely need to parse the files using line endings and characters such as "#"as delimiters.
I haven't gotten around to doing that yet (I have no idea how to do that yet!), but I would like to know if it is possible or if I need to restart my project that doesn't use Core Data...
Please DO NOT just throw links to the apple documentation at me, it's the most confusing thing ever, and feels like it's made for experts only! I need me some human-readable explanations :)
Thanks a bunch for any help and advice you can give me!
It is possible to write a different storage format for Core Data, but it is not easy and it sounds like you are not at a level where that is a possibility (no shame there, I'm not either).
If you are only displaying data from the .po files then there is no need to use CoreData. CoreData is meant to provide a file storage solution. You create/edit data and save it using coredata. If you have no intention to create and edit data then get rid of coredata, it will only get in the way.
I noticed that Apple started using zip archives to replace document packages (folders appearing as a single file in Finder) in the iWork applications. I'm considering doing the same as I keep getting support emails related to my document packages getting corrupted when copying them to a windows fileserver.
My questions is what would be the best way to do this in a NSDocument-based application?
I guess the easiest way would be to create a directory file wrapper, create an archive of it and return it in NSDocument's
- (NSFileWrapper *)fileWrapperOfType:(NSString *)typeName error:(NSError **)outError
But I fail to understand how to create a zip archive of the NSFileWrapper.
If you just want to make a zip file your format (ie, "mydoc.myextension" is actually a zip file), there's no convenient, built-in Cocoa mechanism for creating zip archives with code. Take a look at this Google Code project: ziparchive I don't believe a file wrapper will help in that case, though.
Since you cited iWork, I don't own iWork 09, but previous versions use a package format (ie, NSFileWrapper would be ideal) but zip the XML that describes the document's structure, while keeping attachments (like embedded media, images, etc.) in a resource folder, all within the package. I assume they do this because XML can be quite large for large, complicated documents, but compresses very well because it's text. This results in an overall smaller document.
If indeed Apple has moved to making the entire document one big zip archive (which I would find odd), they'd either be extracting necessary resources to a temp folder somewhere or loading the whole thing into memory (a step backward from their package-based approach, IMO). These are considerations you'll need to take into account as well.
You’ll want to take the data from the file wrapper and feed it into something like ziparchive.
Pierre-Olivier Latour has written an extension to NSData that deals with zip compression. You can get it here: http://code.google.com/p/polkit/
I know this is a little late to the party but I thought I'd offer up another link that could help anyone that comes across this post.
Looks like the ZipBrowser sample from Apple would be a good start http://developer.apple.com/library/mac/#samplecode/ZipBrowser/Introduction/Intro.html
HTH
I've been tasked with maintaining an application originally written in VB6. It has since been imported into VB .Net and to say the least the code is anything but Object Oriented. The code is riddled with classes which contain nothing more than Public Shared attributes(variables) and methods(functions), the result of which restricts the application from opening more than one project at a time.
A project consists of a XML file which contains general project settings, as well as the location to an Access database which contains other project related data. Over the years the format of the XML file has been modified, and an update and versioning strategy has been adopted. The chosen strategy performs an update upon open whenever an old version is encountered. Thus far, updates have only consisted of rearranging data within the XML file or making database schema changes and moving data from the XML file to the database.
Having quite a bit of background in OOP it's easy for me to see that a project should be a self contained object which other objects interact with. However, I fail to see how to apply the chosen update strategy in OOP.
The problem of implementing the chosen update strategy in OOP has kept me from using OOP as of yet. If anyone has experience with such a task, or recommendations on how to proceeded I'd appreciate any assistance you can provide.
Build a class which reads the XML file in, and provides properties/methods/etc based upon the data in that file. When the class writes the XML file back out, have it format in the manner needed for the new version.
So, basically, the class will be able to read in the current version, plus all the older versions, but it will always write out the new version.
Data would be held in internal variables of the class, rather than having to scan the XML file every time you need something.
Adding a VERSION node to your XML file will also help in this case.
You might have answered your own question when you used the word strategy (i.e. the Strategy Design Pattern).
Possibly you could:
Create a project class that knows nothing about conversions but accepts a strategy object.
Create a hierarchy of classes to model each possible conversion strategy.
Use a factory method to build your project object with the right strategy
I don't understand why this is a troubling problem. It could be solved in any number of ways.
If you want to do a full object oriented enterprisey type thing, you could take any subset of the following solution:
Create an interface IProject which
describes how other objects interact
with a project.
Create the current implementation of
Project which implements IProject
and can read and write to the
current version.
Extend Project for each past
version, overriding the xml and
database read methods and having the
constructor call write when these
classes are instanced
For extra enterpriseyness, create a
ProjectFactory, which detects the
version of the file and instanciates
the correct version.
If further versions are needed,
rewrite the current Project to do
the same thing as past projects,
accessing the new version of Project
with all the reads and then calling
write.
The advantage of this solution is that you can continue meandering about with different versions and each new version only requires the ability to be updated to from the previous version, with all previous versions cascading up to the second to last version.