Re: Help with some logic, best way to update a container.

"Simon" <>
Sun, 8 Feb 2009 06:56:09 +0200
"Joseph M. Newcomer" <> wrote in message

But you said explicitly, if a value is in the old container but not in the
new container,
you want to delete it from the old container. Suppose you had

old: {A=1 B=2 C=3}
new{A=4 B=5 C=6}
result: {A=4 B=5 C=6}

old {A=1 B=2 C=3}
new {C=7 D=8}
result: {C=7 D=8}

As I said, both containers are not similar, the 'new' container contians
some information, but not all.
This would be true if the map was that straight forward 1-1 mapping of
values, but assuming I have something like

struct _MYSTRUCT
int some_value;
int some_othervalue;
void* some_pointer;
std::map<int, _MYSTRUCT*> _data;

and the new data was something diferent

int some_value;
int some_othervalue;

void Update( const std::map<int, _MYSTRUCTB>& newData )

In the example above
I would update 'some_value' and 'some_othervalue' where the ID is found in
_data (spec-1)
I would create/new _MYSTRUCT* using the values given by newData, and make
some_pointer NULL. (spec-2)
I would delete items id that are not present in newData (spec-3).


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