is std::map what I need in this case ?
Author
Hi,
I've got a resource manager. Each resource has an ID (an unsigned int which keeps incrementing) and is stored in a std::vector.
The rest of the program always uses ID. So when something need access to a given resource, I have to iterate through the vector and test each ID to return a pointer to the resource.
I would like to speed that up by having a sort of system in which I pass the ID, and it returns me the index in the std::vector in the fastest way.
I think std::map is what I need, but as I don't know the stl really well, I would know if there is something better for this job before using std::map.
Thx for any help.
Yes, you could certainly use a std::map. Just search for C++ map tutorial, or something similar on google, and you'll find many useful sites that explain how to use maps. You'd probably want to do something like
map<int, Resource> resources;
Where Resource is your resource class. There's no need to use a separate vector, as it would just be an unnecessary level of indirection.
Have fun using maps!
map<int, Resource> resources;
Where Resource is your resource class. There's no need to use a separate vector, as it would just be an unnecessary level of indirection.
Have fun using maps!
I would agree that a std::map would suit you quite perfectly in this case. But as Deniz has said, you do not need to do all of that vector stuff. Here's a little example:
So definitly take a look at maps, those methods are the simplest, but highly advised against! You will be using Iterators instead to handle that stuff. If you need a 'real example' one can be done, it's late now [wink]
class Resource{// ... stuff ...};// Resourcesmap<int, Resource*> resourceMap;Resource* r1 = new Resource;Resource* r2 = new Resource;Resource* r3 = new Resource;// ... fill in data ...// Old hackish, dangerous way to do an insert into a mapresourceMap[r1->id] = r1;resourceMap[r2->id] = r2;resourceMap[r3->id] = r3;// Then when you need to get a resourcesint id = 1;// Once again, Old hackish, dangerous way to do an insert into a mapResource* cur = resourceMap[id]So definitly take a look at maps, those methods are the simplest, but highly advised against! You will be using Iterators instead to handle that stuff. If you need a 'real example' one can be done, it's late now [wink]
Yes, once you have familiarized yourself with std::map's functionality, you can look into using its insert and find functions etc. Also, look at how Drew_Benton has suggested to declare the map, he's using a pointer to a Resource object, which you will probably want to do. In fact you will have to if you're going to use polymorphism (i.e. using subclasses of Resource).
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