Instruction Manual

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©Copyright 1996 Rogue Wave Software
Chapter 14: Persistence
Levels of Persistence❍
A Note About Terminology■
About the Examples in this Section■
No Persistence❍
Simple Persistence❍
Two Examples of Simple Persistence■
Isomorphic Persistence❍
Isomorphic versus Simple Persistence■
Isomorphic Persistence of a Tools.h++ Class■
Designing Your Class to Use Isomorphic Persistence■
Writing rwSaveGuts and rwRestoreGuts Functions■
Isomorphic Persistence of a User-designed Class■
Polymorphic Persistence❍
Operators■
Designing your Class to Use Polymorphic Persistence■
Polymorphic Persistence Example■
A Few Friendly Warnings❍
Always Save an Object by Value before Saving the Identical Object by
Pointer
■
Don't Save Distinct Objects with the Same Address■
Don't Use Sorted RWCollections to Store Heterogeneous RWCollectables■
Persistence is the ability to save an object to a file or a stream and then restore that object from
the file or stream. Persistence is a very important feature of objects because it facilitates the
exchange of objects between processes. Using persistence and working through streams, you
can send objects from one program to another, or from one user to another. You can also save a
persistent object to a file on a disk, and restore it from disk at another time, or in another place.