RangeDeserializerBuilder example does not works

[latot]

Hi, I'm following the example to read a columns from a xlsx:

  let mut excel: Xlsx<_> = open_workbook(path)?;

  let sheet_names = excel.sheet_names();

  if sheet_names.len() != 1 {
    todo!()
  }

  let range = excel.worksheet_range(sheet_names[0].as_str())?;
  let iter_records =
    RangeDeserializerBuilder::with_headers(&["column"])
    .from_range(&range)?;

But it fails with:

error[E0283]: type annotations needed for `RangeDeserializer<'_, Data, D>

Please fix the examples :3

Thx!

[tafia]

I suppose you are trying to deserialize into unknown type?

In the example, in the loop, there is some explicit type set :

 if let Some(result) = iter.next() {
        let (label, value): (String, f64) = result?;  // <-- HERE
        assert_eq!(label, "celsius");
        assert_eq!(value, 22.2222);
        Ok(())
    } else {
        Err(From::from("expected at least one record but got none"))
    }

Alternatively you can set it on the builder:

  let iter_records =
    RangeDeserializerBuilder::<_, String>::with_headers(&["column"])
    .from_range(&range)?;

[latot]

Hi yes, it is set after, but the code fails when creating the RangeDeserializerBuilder, actually the only way to call it is specifying the types, or the compiler will complains.

[McDonnellJoseph]

Hello, I'm also running into the same issue and I'm not quite sure I understand what's happening.

Following examples from calamine ReadMe:

I have the following code :

    let mut workbook: Xlsx<_> = open_workbook(file_path).unwrap();
    let mut sheet = workbook.worksheet_range("Feuil1").unwrap();
    let mut iter = RangeDeserializerBuilder::new()
            .from_range(&sheet)?;

and this doesn't compile and returns the following error.

error[E0283]: type annotations needed for `RangeDeserializer<'_, calamine::Data, D>`
   --> src/xlsx_reader.rs:13:9
    |
13  |     let mut iter = RangeDeserializerBuilder::new()
    |         ^^^^^^^^
14  |             .from_range(&sheet)?;
    |              ---------- type must be known at this point
    |
    = note: cannot satisfy `_: serde::de::DeserializeOwned`
note: required by a bound in `RangeDeserializerBuilder::<'h, H>::from_range`
   --> /home/joseph/.cargo/registry/src/index.crates.io-6f17d22bba15001f/calamine-0.24.0/src/de.rs:205:12
    |
199 |     pub fn from_range<'cell, T, D>(
    |            ---------- required by a bound in this associated function
...
205 |         D: DeserializeOwned,
    |            ^^^^^^^^^^^^^^^^ required by this bound in `RangeDeserializerBuilder::<'h, H>::from_range`
help: consider giving `iter` an explicit type, where the type for type parameter `D` is specified
    |
13  |     let mut iter: RangeDeserializer<'_, calamine::Data, D> = RangeDeserializerBuilder::new()
    |                 ++++++++++++++++++++++++++++++++++++++++++

I'm new to rust so this may be just a rookie mistake but AFAIK the example code shown for calamine does not compile. Thanks for any help :smile: