Re: Dynamically adding a derived attribute
Re: Dynamically adding a derived attribute
- Subject: Re: Dynamically adding a derived attribute
- From: Kieran Kelleher <email@hidden>
- Date: Thu, 26 Apr 2007 06:06:53 -0400
it might be worthwhile to look at the Wonder source code in EOAccess/
EOControl *Utilities.java for hints. IIRC they do this on the fly for
the count* convenience methods.
On Apr 26, 2007, at 12:23 AM, Lachlan Deck wrote:
Hi there,
I'm getting tired of manually adding to each entity a
'derivedCount' attribute defined as:
{
columnName = "";
definition = "count(*)";
externalType = BIGINT;
name = derivedCount;
valueClassName = NSNumber;
valueType = l;
},
So I'm attempting to add it when the application launches
(unsuccessfully so far) whilst the entity is loading.
I think the piece of the puzzle I'm missing is how to set this
attribute as a non-class property. Any ideas?
EOEntity anEntity; // assume exists
if ( anEntity.attributeNamed( "derivedCount" ) == null ) {
EOAttribute derivedCount;
derivedCount = new EOAttribute();
derivedCount.setValueType( "l" );
derivedCount.setExternalType( "BIGINT" );
derivedCount.setName( "derivedCount" );
derivedCount.setClassName( "java.lang.Long" );
derivedCount.setColumnName( "__temp__" );
anEntity.addAttribute( derivedCount );
derivedCount.setDefinition( "count(*)" );
derivedCount.setReadOnly( true );
}
No exceptions get thrown here, however when I attempt to do a fetch
it complains about the non-existing attribute in the schema.
Thanks.
with regards,
--
Lachlan Deck
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