Ruby CoreData Tutorial

December 31, 2005 § 1 Comment

As part of my DARC strategy, I’m working on creating a Rails Adaptor for CoreData. The first step is simply getting
CoreData to talk to Ruby. Fortunately, RubyCocoa 0.4.2 adds CoreData support, so this should be
doable.

I have created a file — cdcli.rb — which implements Apple’s “Low-Level Core Data Tutorial” in Ruby, resulting
in a command-line utility which programmatically creates and uses a Core Data
model.

Update:
With important help from Chris Thomas of RubyCocoa — it works! In addition, he
pointed me to the Xcodes templates, which allowed me to do the same example
(much more simply!) as a Ruby Core Data
Document-based
Application
.

[Read More] for
notes on what I am learning along the way.

RELEASE NOTES
for cdcli.rb:

(with
updates
from Chris Thomas)
1. Must use RubyCocoa 0.4.2, as that is the first
version with Core Data support
2. require ‘osx/coredata’
as well as ‘osx/cocoa’
3. Remember to prefix everything with
“OSX::”
(or use include
OSX)
4. Trailing ‘()’ not needed, but helps me
remember what’s a function
5. p.14: Do
not
use AutoRelease or create a pool
(Ruby
takes care of all that)
6. p. 19:
OSX::NSFileManager#fileExistsAtPath:isDirectory:
requires a pointer
7. -> pass normally, trust RubyCocoa to “do
the right thing”
8. -> pass in Boolean as string “NO”; seems to
work…
(should probably pass ‘nil’ or
maybe ‘^c’)
9. p. 22: External constants implemented as
methods:
STORE_TYPE =
OSX::NSXMLStoreType()
10. p. 22: Same issue with
error
in
OSX::NSPersistentStoreCoordinator.addPersistentStoreWithType
11. ->
error =
OSX::NSError.alloc.init
# to ensure right type
(may not be needed)
12. p. 23: Have
managedObjectContext
take ‘mom’ as a parameter, passed in by main
13. -> will be needed there for entity lookup,
though it is designed to be called twice
14. p. 25: Define Run class in same file, for
simplicity (gotta love Ruby’s dynamism 🙂
15. p. 26: Define “processID” as a primitive; no
real scalars in Ruby, and @ processID causes problems
16. p. 27:
awakeFromInsert
requires explicit:
ns_overrides
‘awakeFromInsert’
17. By jove, I think it works! (as Tue Jan 3rd @
3 PM PST)
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§ One Response to Ruby CoreData Tutorial

  • acaro says:

    Hi Ernest, I have reimplemented the Low-level Core Data Tutorial starting from your implementation so that it works under current RubyCocoa releases. It was really useful to have a head start into the matter, and your sample code was of great help, but I found that it does not run under RubyCocoa 0.10. For reference, my implementation can be found at this link. Any comments or suggestions are welcome!

    sergio

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