Trait ScalarValue

pub trait ScalarValue: Sized {
    // Required method
    fn from_row(row: &Row, col: usize) -> Option<Self>;
}

Expand description

Trait for types that can be extracted from a scalar query result.

This trait enables the generic Connection::execute_scalar_query method, similar to C++’s executeScalarQuery<T>() template.

§Implementing Custom Types

You can implement this trait for custom types to use them with execute_scalar_query:

impl ScalarValue for MyType {
    fn from_row(row: &Row, col: usize) -> Option<Self> {
        row.get_string(col).map(|s| MyType::parse(&s))
    }
}

Extracts a value of this type from a row at the given column.

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.