How to initialize std::fs:File without opening a file?

[dauspamfilter]

Hi there,

I am trying around with Actix and would like to store a std::fs::File in a struct, that might be used, or actually might not be used opening a file. Problem is, I need to initialize that variable with something.... but with what? As this is also in a potential multi threaded environment, i am trying to put a Mutex arround it.

struct AppState {
    data_file: Mutex<std::fs::File>
}
...
let my_var = AppState{data_file: Mutex::new(<WHAT TO PUT HERE?>)};

As the file is not always used, I would like to start with an 'empty' file var. as the file will be read quite often I do want to keep it open to not always seek a position in the file...

Any idea?

[asymmetrikon]

Why not Mutex<Option<File>>? None when it's unloaded, Some when it's open.

I suppose it depends on how the code should behave when the File is "empty".

[dauspamfilter]

Looks like an idea.... at least the initialization compiles, will need to put more code around it.. will let you know! Thanks!

[kornel]

You could also wrap the Mutex in once_cell — Rust library // Lib.rs

[dauspamfilter]

The solution with the Option did the trick for me! Thanks!