diesel/
row.rs

1//! Contains the `Row` trait
2
3use backend::Backend;
4use deserialize::{self, FromSql};
5
6/// Represents a single database row.
7/// Apps should not need to concern themselves with this trait.
8///
9/// This trait is only used as an argument to [`FromSqlRow`].
10///
11/// [`FromSqlRow`]: ../deserialize/trait.FromSqlRow.html
12pub trait Row<DB: Backend> {
13    /// Returns the value of the next column in the row.
14    fn take(&mut self) -> Option<&DB::RawValue>;
15
16    /// Returns whether the next `count` columns are all `NULL`.
17    ///
18    /// If this method returns `true`, then the next `count` calls to `take`
19    /// would all return `None`.
20    fn next_is_null(&self, count: usize) -> bool;
21
22    /// Skips the next `count` columns. This method must be called if you are
23    /// choosing not to call `take` as a result of `next_is_null` returning
24    /// `true`.
25    fn advance(&mut self, count: usize) {
26        for _ in 0..count {
27            self.take();
28        }
29    }
30}
31
32/// Represents a row of a SQL query, where the values are accessed by name
33/// rather than by index.
34///
35/// This trait is used by implementations of
36/// [`QueryableByName`](../deserialize/trait.QueryableByName.html)
37pub trait NamedRow<DB: Backend> {
38    /// Retrieve and deserialize a single value from the query
39    ///
40    /// Note that `ST` *must* be the exact type of the value with that name in
41    /// the query. The compiler will not be able to verify that you have
42    /// provided the correct type. If there is a mismatch, you may receive an
43    /// incorrect value, or a runtime error.
44    ///
45    /// If two or more fields in the query have the given name, the result of
46    /// this function is undefined.
47    fn get<ST, T>(&self, column_name: &str) -> deserialize::Result<T>
48    where
49        T: FromSql<ST, DB>,
50    {
51        let idx = self
52            .index_of(column_name)
53            .ok_or_else(|| format!("Column `{}` was not present in query", column_name).into());
54        let idx = match idx {
55            Ok(x) => x,
56            Err(e) => return Err(e),
57        };
58        let raw_value = self.get_raw_value(idx);
59        T::from_sql(raw_value)
60    }
61
62    #[doc(hidden)]
63    fn index_of(&self, column_name: &str) -> Option<usize>;
64    #[doc(hidden)]
65    fn get_raw_value(&self, index: usize) -> Option<&DB::RawValue>;
66}
diesel/row.rs

diesel/
row.rs
