Option type problems

[radiobob]

I've used Option a few times but not sure whats going on with this use.
I have a struct field:

pub struct UDPdata{
    pub opt_udp_writer :  option::Option<udp_writer::UDPWData>,
}

In the impl block its first initialised:

let mut opt_udp_writer: option::Option<udp_writer::UDPWData> = None;

Then if I instantiate the type it gets overwritten:

let i_udp_writer = udp_writer::UDPWData::new(arc2, arc3);
opt_udp_writer = Some(i_udp_writer);

The result is written to the structure.
``
UDPdata {
opt_udp_writer : opt_udp_writer,
}`
So far so good. When I go to use it.

match self.opt_udp_writer {
            Some(mut writer) => writer.prime(),  
            None => println!("Address invalid, hardware will not be primed!"),
        }

error[E0507]: cannot move out of self.opt_udp_writer.0 which is behind a mutable reference
--> src\udp\udp_man.rs:111:15
|
111 | match self.opt_udp_writer {
| ^^^^^^^^^^^^^^^^^^^ help: consider borrowing here: &self.opt_udp_writer
112 | Some(mut writer) => writer.prime(),
| ----------
| |
| data moved here
| move occurs because writer has type UDPWData, which does not implement the Copy trait
Usual error I know but I can't see the problem here.

[Miiao]

Nothing wrong happened with Option. Your writer variable has been moved. Try to borrow it instead of moving.

[H2CO3]

Please post the complete code that produces the error. The snippets you posted don't, in isolation.

[scottmcm]

If you want to modify something in the match body, the usual answer is that you want to pass a mutable reference to the match:

match &mut self.opt_udp_writer {
    Some(writer) => writer.prime(),  
    None => println!("Address invalid, hardware will not be primed!"),
}

[radiobob]

Thanks. The &mut did it and it all runs and works. I'm still at the level of keep trying until it works but I hadn't tried that variation. I'm hoping the penny will drop soon!