How to define complicated lazy_static data without cloning

help
1

I've got some static data tables that are embedded in each other, but are using complex data types (eg. BTreeMap). I'm trying to see if there is a way to avoid cloning data when I'm defining all these tables, but I've had no luck so far. Here is a simplification of what I'm doing:

Playground using clone()

In a nutshell, I have:

struct Table { data: [...] }
struct Catalog { tables: BTreeMap<usize, Table> }
struct Directory { catalogs: BTreeMap<usize, Catalog> }

where there will be a number of Catalogs which are used variously by a large number of Directories. I'm using lazy_static to define the Catalogs and Directories, but when defining each Directory I find I have to clone() the Catalogs which appear in more than one Directory.

Given that the data never changes, and that so much of it is duplicated (in my real use-case), I'm trying to see a way to compile it in, but avoid making multiple copies of the various Catalogs, if at all possible.

I feel as though I should be able to do something by storing static references to the Catalogs in the Directories, but I haven't been able to see a way get those static references from lazy_static refs, while defining another lazy_static ref.

Is there something I'm missing, or an different appoach I should be looking at to solve this sort of situation cleanly? Any advice appreciated.

  • Liam
2

&*THE_CATALOG. When using lazy_static, you actually get a static type that implements Deref to your type (Catalog), and a static of that type. They share the name you give in the macro call.

(Tip: under Tools, you can Expand Macros.)

3 Likes
3

Thank you for that! I figured it would exactly be something pretty straight-forward that I hadn't tried!

4

This is one of the first things in the crate docs.

5

It's been a while since I directly referred to the docs, I admit. I should always go back there first. Thanks for the reminder.

6

This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.