Rust mistyping for csv reading - rust

Question

use walkdir::WalkDir;
use std::ffi::OsStr;
use rusqlite::{params, Connection, Result};
use std::error::Error;
use std::io;
use std::process;
use std::path::Path;
use serde::{Serialize, Deserialize};
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Trade {
id: usize,
price: f64,
quantity: f64,
quoted_quantity: f64,
time: i64,
is_buyer_maker: bool,
is_best_match: bool,
}
fn process_csv(file: &Path, db: &Connection) -> Result<(), Box<dyn Error>> {
let mut rdr = csv::Reader::from_path(file)?;
for result in rdr.records() {
match result.deserialize::<Trade>() {
Ok(s) => {
db.execute("INSERT INTO trades (id, price, quantity, quoted_quantity, time, is_buyer_maker, is_best_match) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)",
params![s.id, s.price, s.quantity, s.quoted_quantity, s.time, s.is_buyer_maker, s.is_best_match])?;
},
Err(e) => println!("Failed to deserialize: {}", e),
}
}
}
fn main () -> Result<(), Box<dyn Error>> {
let conn = Connection::open("bot.db")?;
conn.execute(
"CREATE TABLE trades (
id INTEGER PRIMARY KEY,
price REAL NOT NULL,
quanity REAL NOT NULL,
quoted_quatity REAL NOT NULL,
time INTEGER NOT NULL,
is_buyer_maker INTEGER NOT NULL,
is_best_match INTEGER NOT NULL,
)",
[],
)?;
for entry in WalkDir::new("E:/binance-public-data/python/data/spot/monthly/trades/").into_iter().filter_map(|e| e.ok()) {
println!("Processing: {}", entry.path().display());
if let Err(e) = process_csv(entry.path(), &conn) {
println!("Processing failed: {}", e);
}
}
Ok(())
}
error[E0599]: no method named `deserialize` found for enum `Result` in the current scope
--> src/lib.rs:24:22
|
24 | match result.deserialize::<Trade>() {
| ^^^^^^^^^^^ this is an associated function, not a method
|
= note: found the following associated functions; to be used as methods, functions must have a `self` parameter
note: the candidate is defined in the trait `_::_serde::Deserialize`
--> /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.127/src/de/mod.rs:537:5
|
537 | / fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
538 | | where
539 | | D: Deserializer<'de>;
| |_____________________________^
help: use associated function syntax instead
|
24 | match Result::<StringRecord, csv::Error>::deserialize::<Trade>() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: disambiguate the associated function for the candidate
|
24 | match _::_serde::Deserialize::deserialize(result) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0308]: mismatched types
--> src/lib.rs:23:5
|
21 | fn process_csv(file: &Path, db: &Connection) -> Result<(), Box<dyn Error>> {
| -------------------------- expected `Result<(), Box<(dyn StdError + 'static)>>` because of return type
22 | let mut rdr = csv::Reader::from_path(file)?;
23 | / for result in rdr.records() {
24 | | match result.deserialize::<Trade>() {
25 | | Ok(s) => {
26 | |
... |
31 | | }
32 | | }
| |_____^ expected enum `Result`, found `()`
|
= note: expected enum `Result<(), Box<(dyn StdError + 'static)>>`
found unit type `()`
help: try using a variant of the expected enum
|
23 | Ok(for result in rdr.records() {
24 | match result.deserialize::<Trade>() {
25 | Ok(s) => {
26 |
27 | db.execute("INSERT INTO trades (id, price, quantity, quoted_quantity, time, is_buyer_maker, is_best_match) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)",
28 | params![s.id, s.price, s.quantity, s.quoted_quantity, s.time, s.is_buyer_maker, s.is_best_match])?;
...
I want to put my data into a sqlite database. I have a bunch of csvs I need to go through and read their data. I do not know how to work around these errors. I've tried reading on the csv documentation but I still get errors with the return types. Also not sure how to deal deserialize.

Answer 1

Your first error is because you're calling csv's .deserialize() on the wrong variable, it should be called on the reader. Change:
for result in rdr.records() {
match result.deserialize::<Trade>() {
to:
for result in rdr.deserialize::<Trade>() {
match result {
Your second error is from simply not returning a success at the end of your process_csv function:
fn process_csv(file: &Path, db: &Connection) -> Result<(), Box<dyn Error>> {
// ...snip...
Ok(()) // <--------
}
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