Oh... I just tried this with a Foo.java class:
public static class Util extends ERXGenericRecordClazz<Foo> { }
public static final Util util = new Util();
Then I can do stuff like this:
Foo aFoo = Foo.util.objectWithPrimaryKeyValue(anEditingContext, 5);
EOEntity entity = Foo.util.entity();
String entityName = Foo.util.entityName();
int count = Foo.util.objectCountWithQualifier(anEditingContext,
aQualifier);
NSArray<Foo> allFoos = Foo.util.allObjects(anEditingContext);
...
I think I get it now. :-) And the utility methods are overridable because I
can put my own implementation in the definition of my Util static inner class.
I like util better than clazz.
Thanks
On Dec 15, 2010, at 5:51 PM, Ricardo J. Parada wrote:
>
>
> I see that the root EOEnterpriseObjectClazz has a bunch of utility methods.
> For example, createAndInsertObject(), allObjects(), objectFromRawRow(),
> objectWithPrimaryKeyValue(), entityName(), entity(),
> createFetchSpecification(), objectCountWithQualifier(), etc.
>
> And they are only defined once instead of each and every _Foo.java.
>
>
>
>
>
> On Dec 15, 2010, at 5:31 PM, David Holt wrote:
>
>>
>> On 2010-12-15, at 1:43 PM, Ricardo J. Parada wrote:
>>
>>> Thanks David.
>>>
>>> I noticed those __Clazz classes are then declared in the EOs as "public
>>> static class". I read the article below to figure what that meant. I'm
>>> still learning java I guess :-)
>>>
>>> http://www.javaworld.com/javaworld/javaqa/2001-08/01-qa-0817-static.html?page=1
>>>
>>> So I'm trying to put it together. My Foo.java would have a clazz static
>>> variable referencing an instance of FooClazz. I can add methods to
>>> FooClazz in my Foo.java.
>>> So then FooClazz extends _FooClazz which could have some static methods.
>>>
>>> Are we saying that when I define my FooClazz methods I implement them by
>>> calling _FooClazz static methods or I can rewrite (i.e. override) if needed?
>>>
>>> I think I'm getting there... I ought to try it I guess. :-)
>>
>> I think the key to the use of Clazz in EOs is this line from the article
>> above:
>>
>> "Instead, instances of Justification act as constants that work with any
>> instance of Text. That's why we can get away with declaring Justification
>> static; it is independent of any specific Text instances."
>>
>> The methods inside whatever class (Clazz) you declare as static inside an EO
>> should be independent of any specific instance. You can call something like
>> People.clazz.currentUser located inside the Person class because it isn't
>> dependent on an instance of the Person class. The "currentUser" should
>> return the same result regardless of where you're calling the accessor from,
>> whereas something like a fullName() method can't be in the static member
>> class because it relies on a specific Person instance to be able to give you
>> a result.
>>
>> If you look at Bug.java, you'll see the static BugClazz contains things like
>> qualifiers, fetchSpecification and arrays of objects that shouldn't be
>> dependent on a specific instance of Bug.
>>
>> That's my understanding from reading the above article and watching the
>> errors that Eclipse gives me when I try to access a static method or
>> variable incorrectly.
>>
>> HTH,
>>
>> David
>>
>>
>>>
>>>
>>>
>>> On Dec 14, 2010, at 5:57 PM, David Holt wrote:
>>>
>>>>
>>>> On 2010-12-14, at 2:20 PM, Ricardo J. Parada wrote:
>>>>
>>>>>
>>>>> I've always wondered what that clazz thingy is. I'm still not sure. I
>>>>> read the javadoc on EOEnterpriseObjectClazz but still I don't quite get
>>>>> it.
>>>>> What is it? Maybe a little example will go a long way in understanding.
>>>>> :-)
>>>>
>>>> Hi Ricardo,
>>>>
>>>> You're not alone :-)
>>>>
>>>> To date I've been following BugTracker as an example to let me integrate
>>>> the pattern into my D2W applications to give me really fine control of
>>>> what objects I'm displaying in lists.
>>>>
>>>> I'm probably not understanding all that the Clazz pattern adds to the mix,
>>>> but using it has allowed me to start understanding Anjo's example
>>>> BusinessLogic in BugTracker and use the patterns I've found in my own
>>>> code, and I know that it has improved my D2W applications considerably.
>>>>
>>>> Here is an example I use inside DocumentClazz
>>>>
>>>> // Class methods go here
>>>> public static class DocumentClazz extends _Document._DocumentClazz {
>>>>
>>>> public EOFetchSpecification
>>>> fetchSpecificationForWorkingGroupDocumentsForDeletion(WorkingGroup wg) {
>>>> // selected working group, marked for Deletion
>>>> EOFetchSpecification fs =
>>>> Document.fetchSpec().qualify(Document.WORKING_GROUP.eq(wg).and(Document.IS_FOR_DELETION.eq(true)));
>>>> return fs;
>>>> }
>>>> }
>>>>
>>>> Now when I need to get a list of documents from an action triggered from a
>>>> navigation tab in my application I can use a method such as:
>>>>
>>>> // DELETION TAB
>>>> public WOComponent listDocumentsForDeletion() {
>>>> EOEditingContext ec = ERXEC.newEditingContext();
>>>> ec.lock();
>>>> WorkingGroup selectedWG = (WorkingGroup) WorkingGroup.wg(ec);
>>>> try {
>>>> EODatabaseDataSource ds = Document.clazz.newDatabaseDataSource(ec);
>>>> EOFetchSpecification fs =
>>>> Document.clazz.fetchSpecificationForWorkingGroupDocumentsForDeletion(selectedWG);
>>>> ds.setFetchSpecification(fs);
>>>> return (WOComponent) listPageNamed("ListDocumentsForDeletion", ds);
>>>> }
>>>> finally {
>>>> ec.unlock();
>>>> }
>>>>
>>>> }
>>>>
>>>> David
>>>>
>>>>
>>>>>
>>>>>
>>>>> On Dec 14, 2010, at 5:15 PM, David Holt wrote:
>>>>>
>>>>>> Hi Anjo,
>>>>>>
>>>>>> On 2010-12-14, at 1:34 PM, Anjo Krank wrote:
>>>>>>
>>>>>>> There is a reason why stuff in BT is done as it is.
>>>>>>>
>>>>>>> I.e. there is a People.class.setCurrentUser(People user) and
>>>>>>> People.class.currentUser(EOEditingContext ec). Basically it puts all
>>>>>>> the thread storage code (including the key) in People, which is, like,
>>>>>>> good style?
>>>>>>
>>>>>> Absolutely agree. But it was difficult for me to wrap my head around
>>>>>> ERXThreadStorage AND Clazz pattern AND ERCoreBusinessLogic at the same
>>>>>> time. I was just trying to simplify it a little for Jesse. There is no
>>>>>> question that all three together are much more powerful and useful.
>>>>>>
>>>>>>>
>>>>>>> Also, ERXThreadStorage already handles EOs and faulting.
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> David
>>>>>>
>>>>>>>
>>>>>>> Cheers, Anjo
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Am 14.12.2010 um 21:57 schrieb David Holt:
>>>>>>>
>>>>>>>> public static Person currentUser(EOEditingContext ec) {
>>>>>>>> Person currentUser = currentUser();
>>>>>>>> if (currentUser != null && currentUser.editingContext()
>>>>>>>> != ec) {
>>>>>>>> EOEditingContext currentUserEc =
>>>>>>>> currentUser.editingContext();
>>>>>>>> currentUserEc.lock();
>>>>>>>> try {
>>>>>>>> Person localUser = (Person)
>>>>>>>> ERXEOControlUtilities
>>>>>>>>
>>>>>>>> .localInstanceOfObject(ec, currentUser);
>>>>>>>> currentUser = localUser;
>>>>>>>> } finally {
>>>>>>>> currentUserEc.unlock();
>>>>>>>> }
>>>>>>>> }
>>>>>>>> return currentUser;
>>>>>>>> }
>>>>>>>>
>>>>>>>
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>>>>
>>>
>>
>
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