CODEWITHSUNDEEP
rust
ahmelsayed
ahmelsayed

Reputation: 7402

Error 'cannot move out of dereference' when trying to match strings from vector

I am very new to rust and trying to write a command line utility as a way to learn.

I am getting the list of args and trying to match on them

let args = os::args()
//some more code
match args[1].into_ascii_lower().as_slice() {
    "?" | "help" => { //show help },
    "add" => { //do other stuff },
    _ => { //do default stuff }
}

this causes this error 

cannot move out of dereference (dereference is implicit, due to indexing)
match args[1].into_ascii_lower().as_slice() {
      ^~~~~~~

I have no idea what that means, but searching yield this which I didn't completely get, but changing the args[1] to args.get(1) gives me another error

error: cannot move out of dereference of `&`-pointer
match args.get(1).into_ascii_lower().as_slice() {
      ^~~~~~~~~~~

what's going on?

Upvotes: 3

Views: 511

Answers (1)

Levans
Levans

Reputation: 15002

As you can see in the documentation, the type of into_ascii_lower() is (see here) :

fn into_ascii_upper(self) -> Self;

It takes self directly, not as a reference. Meaning it actually consumes the String and return an other one.

So, when you do args[1].into_ascii_lower(), you try to directly consume one of the elements of args, which is forbidden. You probably want to make a copy of this string, and call into_ascii_lower() on this copy, like this : 

match args[1].clone().into_ascii_lower().as_slice() {
    /* ... */
}

Upvotes: 3

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