Parsing JSON with multiple representation in the same attribute

问题

I'm relatively new to Rust, and even more so to Serde, so I'm having trouble finding out if this is even doable. I have a JSON file which has two different representations for the same key:

"coordinates": [
  [
    [
      121.423364,
      24.9913596
    ],
    [
      121.4233327,
      24.9912977
    ],
  ]
]

and this:

"coordinates": [
  [
    121.4472492,
    25.0052053
  ],
  [
    121.4466457,
    25.0028547
  ]
]

There is a two dimensional array and a three dimensional array representing ways in the same attribute. This makes the file hard to serialize.

Here is the code that I implemented:

#[derive(Serialize, Deserialize, Debug)]
struct Geometry {
    #[serde(deserialize_with = "string_or_number", rename = "type")]
    geometry_type: Value,
    #[serde(default, skip_serializing_if = "Vec::is_empty", rename = "coordinates")]
    geometry_coor: Vec<Coordinates>,
    #[serde(default, skip_serializing_if = "Vec::is_empty", rename = "coordinates")]
    geometry_coor2: Vec<Vec<Coordinates>>,
}

#[derive(Serialize, Deserialize, Debug)]
struct Coordinates {
    #[serde(deserialize_with = "string_or_number")]
    longitude: Value,
    #[serde(deserialize_with = "string_or_number")]
    latitude: Value,
}

fn string_or_number<'de, D>(de: D) -> Result<Value, D::Error>
where
    D: serde::Deserializer<'de>,
{
    let helper: Value = Deserialize::deserialize(de)?;

    match helper {
        Value::Number(n) => {
            println!("{:#?}", n.as_f64().unwrap().to_string());
            Ok(Value::Number(n))
        }
        Value::String(s) => Ok(json!(s)),
        _ => Ok(json!(null)),
    }
}

I have trouble in struct Geometry which serializes the file of coordinates.

Are there any ways that I can deal with this kind of form?

回答1:

I got help from the serde-rs developer:

I would recommend using an untagged enum to represent a coordinate array that can be 2d or 3d. Playground link

Here is the code after modification:

#[derive(Serialize, Deserialize, Debug)]
struct Geometry {
    #[serde(deserialize_with = "string_or_number", rename = "type")]
    geometry_type: Value,
    #[serde(default, skip_serializing_if = "Vec::is_empty", rename = "coordinates")]
    geometry_coor: Vec<Coordinates_form>,
}

#[derive(Serialize, Deserialize, Debug)]
#[serde(untagged)]
enum Coordinates_form {
    #[serde(skip_serializing)]
    OneD(Coordinates),
    #[serde(skip_serializing)]
    TwoD(Vec<Coordinates>),
    #[serde(skip_serializing)]
    ThreeD(Vec<Vec<Coordinates>>),
}

#[derive(Deserialize, Debug)]
struct Coordinates {
    #[serde(deserialize_with = "string_or_number")]
    longitude: Value, 
    #[serde(deserialize_with = "string_or_number")]
    latitude: Value,
}

fn string_or_number<'de, D>(de: D) -> Result<Value, D::Error>
where
    D: serde::Deserializer<'de>,
{
    let helper: Value = Deserialize::deserialize(de)?;

    match helper {
        Value::Number(n) => {
            println!("{:#?}", n.as_f64().unwrap().to_string());
            Ok(Value::Number(n))
        }
        Value::String(s) => Ok(json!(s)),
        _ => Ok(json!(null)),
    }
}

来源：https://stackoverflow.com/questions/51890312/parsing-json-with-multiple-representation-in-the-same-attribute

标签

json

rust

serde