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extern crate csv;
extern crate serde;
#[macro_use]
extern crate serde_derive;
extern crate serde_qs as qs;
use serde::de::DeserializeOwned;
use std::default::Default;
#[derive(Debug, PartialEq, Deserialize, Serialize)]
struct Query {
#[serde(deserialize_with = "from_csv")]
r: Vec<u8>,
s: u8,
}
fn main() {
let q = "s=12&r=1,2,3";
let q: Query = qs::from_str(q).unwrap();
println!("{:?}", q);
}
#[test]
fn deserialize_sequence() {
let q = "s=12&r=1,2,3";
let q: Query = qs::from_str(q).unwrap();
let expected = Query {
r: vec![1, 2, 3],
s: 12,
};
assert_eq!(q, expected);
}
fn from_csv<'de, D, T>(deserializer: D) -> Result<Vec<T>, D::Error>
where
D: serde::Deserializer<'de>,
T: DeserializeOwned + std::str::FromStr,
<T as std::str::FromStr>::Err: std::fmt::Debug,
{
deserializer.deserialize_str(CSVVecVisitor::<T>::default())
}
/// Visits a string value of the form "v1,v2,v3" into a vector of bytes Vec<u8>
struct CSVVecVisitor<T: DeserializeOwned + std::str::FromStr>(std::marker::PhantomData<T>);
impl<T: DeserializeOwned + std::str::FromStr> Default for CSVVecVisitor<T> {
fn default() -> Self {
CSVVecVisitor(std::marker::PhantomData)
}
}
impl<T: DeserializeOwned + std::str::FromStr> serde::de::Visitor<'_> for CSVVecVisitor<T>
where
<T as std::str::FromStr>::Err: std::fmt::Debug, // handle the parse error in a generic way
{
type Value = Vec<T>;
fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(formatter, "a str")
}
fn visit_str<E>(self, s: &str) -> std::result::Result<Self::Value, E>
where
E: serde::de::Error,
{
// Treat the comma-separated string as a single record in a CSV.
let mut rdr = csv::ReaderBuilder::new()
.has_headers(false)
.from_reader(s.as_bytes());
// Try to get the record and collect its values into a vector.
let mut output = Vec::new();
for result in rdr.records() {
match result {
Ok(record) => {
for field in record.iter() {
output.push(
field
.parse::<T>()
.map_err(|_| E::custom("Failed to parse field"))?,
);
}
}
Err(e) => {
return Err(E::custom(format!(
"could not deserialize sequence value: {:?}",
e
)));
}
}
}
Ok(output)
}
}
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