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View Code? Open in Web Editor NEWDerive `FromRow` trait to automaticly convert postgres rows to structs.
Home Page: https://docs.rs/postgres-from-row
License: MIT License
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Trait bounds not met
Unrelated to #10, while I can now get the derive on a struct with a lifetime parameter to compile, I can't get the usage of it in a function to compile.
Minimal example:
// The derive compiles fine now
#[derive(FromRow)]
struct User<'b> {
id: i32,
username: &'b str
}
// However, there's a lifetime issue when trying to use the derived function:
fn get_user_by_id<'c>(db: &mut impl postgres::GenericClient, id: i32) -> Result<User<'c>, postgres::Error> {
let row = db.query_one("SELECT * FROM User WHERE id = $1", &[&id])?;
User::try_from_row(&row)
}
Error:
error[E0599]: the function or associated item `try_from_row` exists for struct `User<'_>`, but its trait bounds were not satisfied
--> tests/integration.rs:14:11
|
6 | struct User<'b> {
| ---------------
| |
| function or associated item `try_from_row` not found for this struct
| doesn't satisfy `User<'_>: FromRow`
...
14 | User::try_from_row(&row)
| ^^^^^^^^^^^^ function or associated item cannot be called on `User<'_>` due to unsatisfied trait bounds
|
= note: trait bound `&str: FromSql<'__from_row_lifetime>` was not satisfied
(Note that this error at the usage site appears both with and without #11, just with the lifetime name in the error changed)
Select specific fields
Support if I don't want to select or return all columns of a table.
Support deserialization of Bigint
Hi there, can you consider adding support to Bigint parsing support? :)
Fails to compile when 'a lifetime parameter used
Reproduction:
use postgres_from_row::FromRow;
#[derive(FromRow)]
struct User<'a> {
username: &'a str,
email: &'a str,
}
Error:
error[E0496]: lifetime name `'a` shadows a lifetime name that is already in scope
--> example-project\src\main.rs:4:10
|
4 | #[derive(FromRow)]
| ^^^^^^^ lifetime `'a` already in scope
5 | struct User<'a> {
| -- first declared here
|
= note: this error originates in the derive macro `FromRow` (in Nightly builds, run with -Z macro-backtrace for more info)
Macro expansion when using 'a (does not compile):
#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
use postgres_from_row::FromRow;
struct User<'a> {
username: &'a str,
email: &'a str,
}
impl<'a> postgres_from_row::FromRow for User<'a>
where
&'a str: for<'a> postgres_from_row::tokio_postgres::types::FromSql<'a>,
&'a str: for<'a> postgres_from_row::tokio_postgres::types::FromSql<'a>,
{
fn from_row(row: &postgres_from_row::tokio_postgres::Row) -> Self {
Self {
username: postgres_from_row::tokio_postgres::Row::get::<
&str,
&'a str,
>(row, "username"),
email: postgres_from_row::tokio_postgres::Row::get::<
&str,
&'a str,
>(row, "email"),
}
}
fn try_from_row(
row: &postgres_from_row::tokio_postgres::Row,
) -> std::result::Result<Self, postgres_from_row::tokio_postgres::Error> {
Ok(Self {
username: postgres_from_row::tokio_postgres::Row::try_get::<
&str,
&'a str,
>(row, "username")?,
email: postgres_from_row::tokio_postgres::Row::try_get::<
&str,
&'a str,
>(row, "email")?,
})
}
}
Surprisingly, it compiles when you use 'b instead of 'a in the struct:
use postgres_from_row::FromRow;
#[derive(FromRow)]
struct User<'b> {
username: &'b str,
email: &'b str,
}
Macro expansion when using 'b (compiles):
#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
use postgres_from_row::FromRow;
struct User<'b> {
username: &'b str,
email: &'b str,
}
impl<'b> postgres_from_row::FromRow for User<'b>
where
&'b str: for<'a> postgres_from_row::tokio_postgres::types::FromSql<'a>,
&'b str: for<'a> postgres_from_row::tokio_postgres::types::FromSql<'a>,
{
fn from_row(row: &postgres_from_row::tokio_postgres::Row) -> Self {
Self {
username: postgres_from_row::tokio_postgres::Row::get::<
&str,
&'b str,
>(row, "username"),
email: postgres_from_row::tokio_postgres::Row::get::<
&str,
&'b str,
>(row, "email"),
}
}
fn try_from_row(
row: &postgres_from_row::tokio_postgres::Row,
) -> std::result::Result<Self, postgres_from_row::tokio_postgres::Error> {
Ok(Self {
username: postgres_from_row::tokio_postgres::Row::try_get::<
&str,
&'b str,
>(row, "username")?,
email: postgres_from_row::tokio_postgres::Row::try_get::<
&str,
&'b str,
>(row, "email")?,
})
}
}
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