In some environments searches are performed in 'single call' fashion, using a transfer object.
E.g. two queries performed by the data services tier before returning combined results to the UI tier:
i. Query for paged search results
ii. Query for a 'count' value representing total possible results
The contract between DataView and IDataProvider does not support a 'single call' environment as the give/take relationship between these classes is biased towards DataView.
DataView expects IDataProvider to provide it's size before providing IDataProvider with its offset and count.
- DataView may have good reasons for needing size before it can provide offset/count.
- But IDataProvider has equally good reasons for needing offset/count before it can provide size.
The circular dependency:
1. DataView calls IDataProvider.size()
2. IDataProvider cannot return size as it cannot start a query until it receives offset/count from DataView
3. These it does not receive until DataView calls IDataProvider.iterator() later on
Others who experienced this problem (with CODE examples):
The suggested solution of caching the combined search results and count value does not work if the search cannot begin until offset and count are available. And writing a custom DataView is not feasible either time wise as I understand that it cannot be done without needing to write a number of other classes too.