2003-10-12 13:00:45 -05:00
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Business Design & Implenmentation Notes
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2003-10-12 13:01:36 -05:00
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Derek Atkins <warlord@mit.edu>
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2003-10-12 13:00:45 -05:00
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Version of October 2003
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The gncTaxTable and gncBillTerm business objects have parent, child,
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refcount, invisible field in thier structures that deserve some
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explanation:
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- a child is a 'frozen' instance of a parent. For example, the tax
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percentage in a particular tax table may change over time, but you
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dont want that change to affect already-posted invoices... So you
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make sure there is an immutable 'copy' (read: child) of the tax
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table when you post the invoice and repoint at the child.
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- a parent can have many children, but it will only have a 'child'
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pointer if the parent has not been modified. Think of this as a
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copy-on-write mechanism. posted invoices will continue to use the
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_same_ child until the parent is modified, at which point a new
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child will be created.
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- invisible means "dont show this in the list". It's so you dont
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get all the children in the tax table list -- you only see parents.
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I suppose this flag could also be called "is-child" as I believe that
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only children can be invisible, and ALL children are invisible.
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- refcount is a listing of how many objects are referencing it.
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Basically, it's letting you know how many customer, vendor, entries,
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etc are referencing e.g. a particular tax table object. mostly this
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was done to make sure you cannot delete an in-use taxtable.
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- children don't use refcounts, only parents do.
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------------------------- end of file ------------------------------
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