Thanks for this! The boost::multiIndex container looks like exactly what my application needs. Your sample program is very through, enough so I think is should be part of the library's examples. Joaquín Mª López Muñoz wrote:
Hello Jeffrey,
Jeffrey Holle ha escrito:
I'm using boost version 1.33.1 and am contemplating using a multiIndex container in my application.
The held object will be something like:
class element { int x; int y; Object *pObject; };
I need 2 ordered_non_unique indices using x and y and one ordered_unique index on pObject.
The problem is that the values of x and y will need to be modified during the life of this container. Since the documentation says these indices are implemented using red-black trees, I think I'm heading for trouble.
No, B.MI is designed to handle these situations :)
However, the multiIndex container seems to have a "modify_key" method. I can guarantee that the pObject value will not change, so if I obtain an iterator to an element based on this index, will I be able to modify either x or y and expect their related indices to still work?
B.MI provides updating mechanisms that take care of all the necessary index internal rearrangement resulting from modifications on the keys:
modify() modify_key() replace()
In your particular case, if the iterator belongs to the pObject-index, modify_key is of no use, since the key here is precisely pObject, which you do not wish to update. You can use then modify(), with accept a modifying functor to be passed a reference to the whole element, or also replace(), wich is passed a new element object to substitute for the old one. In any case, the indices are internally kept in sync.
Please find attached a small snippet showing the various ways you can use the updating facilities of B.MI, both with user-defined modifying functors and by means of the Boost Lambda library. If you have further doubts, don't hesitate to ask.
HTH,
Joaquín M López Muñoz Telefónica, Investigación y Desarrollo
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