Struct slog::PushFnValue [] [src]

pub struct PushFnValue<F>(pub F) where F: 'static + for<'c, 'd> Fn(&'c Record<'d>, PushFnSerializer<'c>) -> Result;

Lazy Value that writes to Serializer

It's more natural for closures used as lazy values to return type implementing Serialize , but sometimes that forces an allocation (eg. Strings)

In some cases it might make sense for another closure form to be used - one taking a serializer as an argument, which avoids lifetimes / allocation issues.

Generally this method should be used if it avoids a big allocation of Serialize-implementing type in performance-critical logging statement.

extern crate slog;
use slog::{PushFnValue, Logger, Discard};

fn main() {
    let _root = Logger::root(Discard, o!( ));
    info!(_root, "foo"; "writer_closure" => PushFnValue(|_ , s| {
                   let generated_string = format!("{}", 1);

Trait Implementations

impl<F> Value for PushFnValue<F> where F: 'static + for<'c, 'd> Fn(&'c Record<'d>, PushFnSerializer<'c>) -> Result

Serialize self into Serializer Read more