Class ComputedMetaMixin

source code

object --+    
         |    
 MetaMixin --+
             |
            ComputedMetaMixin

Known Subclasses:

• rscdef.dddef.DataDescriptor
• , registry.nonservice.NonServiceResource
• , svcs.service.Publication
• , rscdesc.RD
• , svcs.service.Service
• , rscdef.tabledef.TableDef

A MetaMixin for classes that want to implement defaults for unresolvable meta items.

If getMeta would return a NoMetaKey, this mixin's getMeta will check the presence of a _meta_<key> method (replacing dots with two underscores) and, if it exists, returns whatever it returns. Otherwise, the exception will be propagated.

The _meta_<key> methods should return MetaItems; if something else is returned, it is wrapped in a MetaValue.

On copying such metadata, the copy will retain the value on the original if it has one. This does not work for computed metadata that would be inherited.