Merge pull request #1462 from gwenn/owning

OwningRows / OwningStatement examples

examples/owning_rows.rs

@@ -0,0 +1,29 @@
+extern crate rusqlite;
+
+use ouroboros::self_referencing;
+use rusqlite::{CachedStatement, Connection, Result, Rows};
+
+#[self_referencing]
+struct OwningRows<'conn> {
+    stmt: CachedStatement<'conn>,
+    #[borrows(mut stmt)]
+    #[covariant]
+    rows: Rows<'this>,
+}
+
+fn main() -> Result<()> {
+    let conn = Connection::open_in_memory()?;
+    let stmt = conn.prepare_cached("SELECT 1")?;
+    let mut or = OwningRowsTryBuilder {
+        stmt,
+        rows_builder: |s| s.query([]),
+    }
+    .try_build()?;
+    or.with_rows_mut(|rows| -> Result<()> {
+        while let Some(row) = rows.next()? {
+            assert_eq!(Ok(1), row.get(0));
+        }
+        Ok(())
+    })?;
+    Ok(())
+}

examples/owning_rows_self_cell.rs

@@ -0,0 +1,27 @@
+extern crate rusqlite;
+
+use rusqlite::{CachedStatement, Connection, Result, Rows};
+use self_cell::{self_cell, MutBorrow};
+
+type RowsRef<'a> = Rows<'a>;
+
+self_cell!(
+    struct OwningRows<'conn> {
+        owner: MutBorrow<CachedStatement<'conn>>,
+        #[covariant]
+        dependent: RowsRef,
+    }
+);
+
+fn main() -> Result<()> {
+    let conn = Connection::open_in_memory()?;
+    let stmt = conn.prepare_cached("SELECT 1")?;
+    let mut or = OwningRows::try_new(MutBorrow::new(stmt), |s| s.borrow_mut().query([]))?;
+    or.with_dependent_mut(|_stmt, rows| -> Result<()> {
+        while let Some(row) = rows.next()? {
+            assert_eq!(Ok(1), row.get(0));
+        }
+        Ok(())
+    })?;
+    Ok(())
+}

examples/owning_statement.rs

@@ -0,0 +1,30 @@
+extern crate rusqlite;
+use ouroboros::self_referencing;
+use rusqlite::{CachedStatement, Connection, Result, Rows};
+
+/// Caveat: single statement at a time for one connection.
+/// But if you need multiple statements, you can still create your own struct
+/// with multiple fields (one for each statement).
+#[self_referencing]
+struct OwningStatement {
+    conn: Connection,
+    #[borrows(conn)]
+    #[covariant]
+    stmt: CachedStatement<'this>,
+}
+
+fn main() -> Result<()> {
+    let conn = Connection::open_in_memory()?;
+
+    let mut os = OwningStatementTryBuilder {
+        conn,
+        stmt_builder: |c| c.prepare_cached("SELECT 1"),
+    }
+    .try_build()?;
+
+    let mut rows = os.with_stmt_mut(|stmt| -> Result<Rows<'_>> { stmt.query([]) })?;
+    while let Some(row) = rows.next()? {
+        assert_eq!(Ok(1), row.get(0));
+    }
+    Ok(())
+}