I thought I understand it

[piter76]

Hi, I'm creating file explorer, something like mc, and I have an fn:

fn fill_table_with_items(a_table: &mut tableViewType, a_dir: &PathBuf) 

Then, later in code I try to call it which gives me error saying that a_table needs to be mutable:

 table.set_on_submit(move |siv: &mut Cursive, row: usize, index: usize| {
        let value = siv
            .call_on_name(a_name, move |a_table: &mut tableViewType| {//HERE I'm getting the error
/*But if I change it to (note the extra mut in front of  a_tabe) then it works:
mut a_table: &mut tableViewType
*/
                let path: String = a_table.borrow_item(index).unwrap().name.clone();
                fill_table_with_items(&mut a_table, &std::path::PathBuf::from(path));
            })
            .unwrap();

So my question is:
Why do I have to write:

mut a_table: &mut tableViewType

My fn fill_table_with_items(a_table: &mut tableViewType, a_dir: &PathBuf)
takes a_table by &mut so I thought that passing it by &mut would be the correct way to do it which is not. Could somebody please explain that to me?

Thanks

[17cupsofcoffee]

Does it work without the extra mut if you do this?

let value = siv
    .call_on_name(a_name, move |a_table: &mut tableViewType| {
        let path: String = a_table.borrow_item(index).unwrap().name.clone();
        // Remove the &mut here:
        fill_table_with_items(a_table, &std::path::PathBuf::from(path));
})

a_table is already a mutable reference, so adding &mut in front is creating a &mut &mut tableViewType (i.e. a mutable reference to the a_table binding, which is itself a mutable reference to data that lives elsewhere).

[piter76]

Ah yes! Thanks!