How to store actix_web Json to mongodb? - mongodb

Question

Trying to store incomming data into mongo using r2d2-mongodb and actix_web.
#[derive(Serialize, Deserialize, Debug)]
struct Weight {
desc: String,
grams: u32,
}
fn store_weights(weights: web::Json<Vec<Weight>>, db: web::Data<Pool<MongodbConnectionManager>>) -> Result<String> {
let conn = db.get().unwrap();
let coll = conn.collection("weights");
for weight in weights.iter() {
coll.insert_one(weight.into(), None).unwrap();
}
Ok(String::from("ok"))
}
I can't seem to understand what/how I need to convert weight into to use with insert_one.
The above code errors into error[E0277]: the trait bound 'bson::ordered::OrderedDocument: std::convert::From<&api::weight::Weight>' is not satisfied

Answer 1

The signature for insert_one is:
pub fn insert_one(
&self,
doc: Document,
options: impl Into<Option<InsertOneOptions>>
) -> Result<InsertOneResult>
Document is bson::Document, an alias for bson::ordered::OrderedDocument.
Your type Weight does not implement the trait Into<Document>, which is required for weight::into(). You could implement it, but a more idiomatic way would be using the Serialize trait with bson::to_bson:
fn store_weights(weights: Vec<Weight>) -> Result<&'static str, Box<dyn std::error::Error>> {
let conn = db.get()?;
let coll = conn.collection("weights");
for weight in weights.iter() {
let document = match bson::to_bson(weight)? {
Document(doc) => doc,
_ => unreachable!(), // Weight should always serialize to a document
};
coll.insert_one(document, None)?;
}
Ok("ok")
}
Notes:
to_bson returns an enum, Bson, which can be Array, Boolean, Document, etc. We use match to make sure it is Document.
I've used ? instead of unwrap, to make use of the Result return type. Make sure the errors are Into<Error> for your Result type.
Returning &'static str instead of allocating a new String for each request.