NSIncrementalStore has a required method "obtainPermanentIDsForObjects".
To get the ID's I have to create new row's in the database. Then to save the data in
executeRequest:withContext:error:, I have to hit the DB again.
Is there a reason why I shouldn't get new rowID's and save the data at the same time in obtainPermanentIDsForObjects?
The answer is probably not, if your entities have relationships.
To save a relationship, you need to uniquely identify the corresponding objects. Identifying an object requires your internal identifier which can be obtain via the permanent objectID (NSManagedObjectID).
But (some of) your objects won't have a permanent and internal ID yet because they haven't been handled yet in "obtainPermanentIDsForObjects"
In other words first you need to assign permanentID's (and thus also internalID's) before you can save references to them.
Related
I am facing an issue with extended attributes on a document (trying to extend a document table). I created the original table’s PK (FDOC_NBR) in the extended table and linked the two via a foreignKey of the customized original table’s ojb entry (as an “extension” reference-descriptor). I created the bo and dd for the extension and customized the original document’s dd to add the new attributes. On the extended BO itself I also added members (with setters and getters) for the 2 new columns + for the PK column of documentNumber. I also added the new attributes to the documet’s jsp. The pertinent module definition was already extended to include custom dd, ojb, etc. files.
Indeed, when opening the document the new fields are shown- however, when trying to submit the document (regardless of doing anything with the new fields) I get an error-
Error Details: OJB operation; SQL []; ORA-01400: cannot insert NULL
into ("KFSTEM"."TEM_TRVL_ARRANGER_DOC_EXT_T"."FDOC_NBR") ; nested
exception is java.sql.SQLIntegrityConstraintViolationException:
ORA-01400: cannot insert NULL into
("KFSTEM"."TEM_TRVL_ARRANGER_DOC_EXT_T"."FDOC_NBR")
Seems like somehow the system tries to insert a value of NULL into the extension’s PK field, instead of the actual document number. Trying to debug this, in the action’s route method and all the way down to DocumentDaoOjb.save (which is as far down as I can go) I see the document with the real doc number is passed on, so the problem seems to be purely with ojb trying to set this number to the extension table.
Does anyone have any experience with extended attributes on documents that could help shed some light on this?
KFS is using the KNS, and in the Kuali Nervous System, the primary key on the extended attributes object must be set through manual intervention.
In this case, it looks as if you're adding an extended attribute to a transactional document, the Travel Arranger document (TAA), which simplifies things. Basically, you'll need to extend org.kuali.kfs.module.tem.document.TravelArrangerDocument and override prepareForSave to set the document number there (it may be set already since prepareForSave should be called several times during the routing process, but there's no real harm from overwriting that information as the base document's number will remain the same).
Hope this helps!
I've come to really love the couchdb style of organizing and updating data, but there are a few situations where I really need to be able to create an entry and determine if an equivalent entry is already in existence before returning to the user. The only situation that this is absolutely necessary for my application is user registration. I'm fine with having all user registration writes go to a particular, designated couchdb instance known as the "registration-instance".
I want to hash the user_id into some _id to use. Then execute a put with this _id, but fail if the _id is already inserted. I need to return to the user that the user name is already reserved, and I cannot detect the conflict later and resolve it at that point, because the user would be under the impression that they had reserved the user name.
I don't see why couchdb couldn't provide some way to do this, under the assumption that you designate that inserts for a particular "type" of document always are routed to a particular instance.
If you send a single CouchDB server a PUT request for a new user document you should get the behavior you want already.
If the document does not exist then it will create the new document.
If the document does exist then it is guaranteed to return a 409 conflict error. This is due to the fact that you did not supply a _rev property because you aren't trying to update the pre-existing document.
Only when the _id and _rev properties match will CouchDB update the existing document.
You might also want to read up on document update handlers:
http://wiki.apache.org/couchdb/Document_Update_Handlers
You might use an update handler to hash the user_id and dynamically assign the appropriate _id. You can also customize what kind of error response couch sends with an update handler.
Good luck!
I'm designing my first project using Core Data (for iPhone) and Im having some issues that might be related with my design approach.
I'm doing an application that allows the user to create an Order (let's say for a restaurant).
I'm using the graphic designer to model my persistence object (i.e. OrdeMO). I add MO to the ead of each name to indicate its a Managed Object.
I use XCode to create the Managed Object Class automatically.
I have created some "DAO" classes that allows you to search or create a new object in the Managed Context.
Now to my problem.
I want to create an OrderMO object to store the order the user is creating, BUT I don't want it to be part of the context until the user actually places it.
I tried creating the object with [OrderMO alloc] but the object I get is "incomplete" and when I try to set any of its attribute I get an error.
I'm assuming the problem is that I need to create the order IN the context in order to use it. Is that so?
I have considered various options:
Create the object in the context and the user rollback if the user discards the order. The problem is that the user might save other context object during the process (like his prefs) so this doesn't work. Is there a way to create the object "inside a separate transaction" of sorts?
Create a wrapper object that will hold the same data as the MO, and then only create the MO when the user place the order. The downside of this is that I have to maintain a new class.
Create an attribute in the MO, such as "placed", and use to filter my searches in the context. The problem with this one is that I will end up with "trash" objects in the domain (i.e. unplaced orders) and I will have to do some cleanup from time to time...
Do I have any other choice?
Any suggestion is appreciated.
Thanks (for reading this long post!)
Gonso
You should create the OrderMO object in the managed object context and then delete it if the user decides not to place the order.
If the context is saved before the object is deleted, the "trash" object will be deleted from the persistent store on the next save (if the context wasn't saved, the "trash" object will never be saved to the persistent store).
The flag to determine if the order was placed or not does not have to live in the OrderMO object as you suggest in option 3. It could be in the view controller that is tracking the order(s) that are being edited. And, again, you won't have "trash" objects because they will have been deleted.
I want to follow the DDD philosophy and not access entity objects of an aggregate directly. So, i have to call the root object to get the associated entity. But In other cases I dont always want every associated entity to load when the root is called. Is that the purpose of lazy loading?
How do I access entity objects through the root without loading all the associated objects everytime if i disable lazyloading feature of linq?
EDIT:
For example, If I have a Person as the Root Entity, and the Person has Name, Addresses and OwnedProperties. If I want to get a list of People so that I could display their names, I dont necvessarily want to load up Owned Properties every time on the call to the Repository. Conversely, on another page I may want to show a list of OwnedProperties, but do not want the other information to load with the call. what is the simple way of just calling the Person without the owned property entity other than creating a new person object without that owned properties?
I don't thinks that's possible without lazy loading.
Getting all data at once: Eager Loading
Getting data when accessed: Lazy Loading
According to your edit:
What I do in these situations, is create a 'View' class or a 'DTO' class which just contains the properties that I'm interested in.
For instance, I could have a 'PersonView' class which just has a Name property for instance.
Then, using my OR/M mapper (I use NHibernate), I create a HQL query (or Criteria query) which works on my 'Person' entity. Before I execute the query, I tell NHibernate that I want 'PersonView' objects as a result (I specify a projection). Then, NHibernate is smart enough to execute a query that only retrieves the columns that are necessary to populate the PersonView instances.
One way to avoid lazy loading is just using the object 'id'
Is there a way to use form fields that does not correspond to database field for temporary processings?
I.e. I want to add:
temp fields item1, item2
database field sum
button with record hook that sets sum = item1 + item2
As far as I know it's simply not possible with ClearQuest.
I've tried to do something similar and was told by our IBM consultant that the only way is to create a DB field for all variables.
You can't attach data to form fields really - those are representations of the underlying data, not something scripts interact with directly.
Adding temporary data to the underlying record (entity) itself sounds unlikely as well. Perhaps it's possible to abuse the perl API and dynamically attach data to entity objects but I personally wouldn't try it, you're liable to lose your data at the whim of CQ then ;-)
That does not however mean it's impossible to have temporary data.
The best way seems to me to be using the session object, which is explicitly intended for that purpose.
From the helpfile:
IBM Rational ClearQuest supports the
use of sessionwide variables for
storing information. After you create
sessionwide variables, you can access
them through the current Session
object using functions or subroutines,
including hooks, that have access to
the Session object. When the current
session ends, all of the variables
associated with that Session object
are deleted. The session ends when the
user logs out or the final reference
to the Session object ceases to exist.
There's some helpful documentation on this subject in file:///C:/Program%20Files/Rational/ClearQuest/doc/help/cq_api/c_session_vars.htm (Presuming a default installation on a windows machine, of course.)
Translating the code example in there into what you seem to be wanting, first you store the data you have calculated inside the session object:
$session->SetNameValue("item1", $value1);
$session->SetNameValue("item2", $value2);
Then in your calculation hook you retrieve the stored values and set the value of that totals field like this:
my $item1 = GetNameValue("item1");
my $item2 = GetNameValue("item2");
my $sum = $item1 + $item2;
$entity->SetFieldValue("some_totals_record", $sum);
Adjust to taste of course ;-)
ClearQuest schema designers often include 'temporary' fields in their record types. They do this so they perform operations on hooks to generate another value.
For example, for the Notes fields, there is a 'temporary' Notes_entry field that the user types the most recent note into, and when the record is saved, the value is added to the Notes_Log field. The next time the record is edited the Notes_entry field is cleared so the user can type a new Notes_entry.