Question 116296 in Mongodb Question posted in
The official documentation can be found here.

How to collect mongodb::Cursor into a Vec in rust

I’m trying to use the .find() method in mongodb. The output yeilds a mongodb::Cursor. I’m unable to convert the cursor into a vector so that I can wrap them in a json and send it to my front-end. This is the following idea I’ve tried

enter image description here

The following error message is:

the trait bound `Vec<user_model::User>: Extend<Result<user_model::User, mongodb::error::Error>>` is not satisfiednthe following other types implement trait `Extend<A>`

I’ve already included and use futures::StreamExt; and use futures::TryFutureExt; and tried out .try_next() and .map() instead of .collect(), still cant parse it

Tags:

2

Answers


  1. 0

    Here is how I managed this in one of my projects.
    I simply iterate over the cursor calling next and push each item in a vector. I used the Document type to collect the results.
    Using a match for each result allows to handle the errors properly, because extraction may fail.

    let mut results: Vec<Document> = Vec::new();

while let Some(result) = cursor.next().await {
    match result {
        Ok(document) => {
            results.push(document);
        }
        _ => {
            return HttpResponse::InternalServerError().finish();
        }
    }
}
    Login or Signup to reply.
  2. 0

    Converting an element in the cursor to a User might fail. You may only collect into a Vec of Result with .collect().

    let serial: Vec<Result<User, _>> = users.collect().await;

    The easy way to get to Vec<User> here would be to use .try_collect(). Just make sure to handle the Err correctly and not just use unwrap as I’ve done here.

    let serial: Vec<User> = users.try_collect().await.unwrap();
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search