Overriding WODisplayGroup methods
Overriding WODisplayGroup methods
- Subject: Overriding WODisplayGroup methods
- From: email@hidden
- Date: Wed, 14 Dec 2005 12:05:25 -0500
Hi,
I would like to override a few WODisplayGroup methods, namely
displayNextBatch and displayPreviousBatch. Currently my WOComponent
has a WODisplayGroup containing a WOBatchNavigationBar used to change
the displayed objects on my page. I would like to perform some
additional logic before calling the "super" displayNextBatch method.
For example, I want to see if the user currently has a boolean flag
set to indicate they are editing the one of the current objects
before actually displaying the next batch of objects in the display
group.
It seems as if I could simply extend the WODisplayGroup to a custom
class, then override the specific methods, and call super when
appropriate. However, after doing this, I cannot get the page to
even load from the start.
Here is the snippet of modified code
public class LocalizationCodePage extends SecuredPageComponent {
public MyDisplayGroup localizationCodesDG;
public LocalizationCode localization;
public boolean isEditingLocalization;
public class MyDisplayGroup extends WODisplayGroup {
public Object displayNextBatch() {
System.out.println("I am about to display the next batch of
objects in MyDisplayGroup");
if (isEditingLocalization) {
System.out.println("Warning: you are currently editing an
existing object in the display group");
// TO DO : Eventually put some additional logic here
}
return(super.displayNextBatch());
}
}
.
.
.
When I attempt to load the page, I now get :
Error: com.webobjects.foundation.NSForwardException
[java.lang.IllegalArgumentException] While trying to set the field
"localizationCodesDG" on an object of type LocalizationCodePage we
expected a LocalizationCodePage$MyDisplayGroup but received a
com.webobjects.appserver.WODisplayGroup with a value of sortOrdering=
() qualifier=null localKeys=() insertedObjectDefaultValues={}
numberOfObjectsPerBatch=2>. This often happens if you forget to use a
formatter.
From researching on the list, I seemed as if I may need to manually
change the cooresponding .woo file as well (e.g. change line
class=WODisplayGroup to class=MyDisplayGroup).
I edited the .woo file to:
{
"WebObjects Release" = "WebObjects 5.0";
encoding = NSMacOSRomanStringEncoding;
variables = {
localizationCodesDG = {
class = MyDisplayGroup;
dataSource = {
class = EODatabaseDataSource;
editingContext = "session.defaultEditingContext";
fetchSpecification = {
class = EOFetchSpecification;
entityName = LocalizationCode;
fetchLimit = 0;
isDeep = YES;
};
};
fetchesOnLoad = YES;
formatForLikeQualifier = "%@*";
localKeys = ();
numberOfObjectsPerBatch = 2;
selectsFirstObjectAfterFetch = YES;
sortOrdering = ({class = EOSortOrdering; key = code;
selectorName = "compareAscending:"; });
};
};
}
After rebuilding and launching my app, I got another error:
Error: com.webobjects.foundation.NSForwardException
[java.lang.IllegalArgumentException] Attempt to insert null object
into an com.webobjects.foundation.NSMutableDictionary.
Any suggestions? Sorry again for another newbie question.
Thanks,
Kev
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