Mastering PowerBuilder

Nested Storages

In the above example, we have stored the sub-storage up to one level. The following example shows saving a sub-storage in a sub-storage.

OLEStorage lOLEStorage1, lOLEStorage2, lOLEStorage3 Integer lResult lOLEStorage1 = Create OLEStorage lOLEStorage2 = Create OLEStorage lOLEStorage3 = Create OLEStorage lResult = ole_control1.Open( "c:\workdir\3.doc" ) If lResult <> 0 Then goto CompleteExecution lResult = lOLEStorage1.Open( "c:\workdir\1.ole" ) If lResult <> 0 Then goto CompleteExecution lResult = lOLEStorage2.Open( "Months", StgReadWrite!, & StgExclusive!, lOLEStorage1 ) If lResult <> 0 Then goto CompleteExecution lResult = lOLEStorage1.Save() If lResult <> 0 Then goto CompleteExecution lResult = lOLEStorage3.Open( "Dates", StgReadWrite!, & StgExclusive!, lOLEStorage2 ) If lResult <> 0 Then goto CompleteExecution lResult = ole_control1.SaveAs( lOLEStorage3, "3.doc" ) If lResult <> 0 Then goto CompleteExecution CompleteExecution: lOLEStorage1.Close() lOLEStorage2.Close() lOLEStorage3.Close() Destroy lOLEStorage1 Destroy lOLEStorage2 Destroy lOLEStorage3

This example does not make use of streams, to make the example more simple. After executing the script, the internal storage looks as shown in the following picture.

Saving the nested storage is like transactions. In a transaction, unless you commit the outer-most transaction, the transaction is not complete. For example,

Begin Tran Tran1

Begin Tran Tran2

…

…

Commit Tran Tran2

This doesn't complete the transaction, However calling "Commit Tran Tran1" instead of "Commit Tran Tran2" will commit all the nested transactions. Saving nested sub-storages also similar to this. You need call Save() for the root storage file, not for the sub-storages.

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