Struct slog::PushFnValue [−][src]
pub struct PushFnValue<F>(pub F)
where
F: 'static + for<'c, 'd> Fn(&'c Record<'d>, PushFnValueSerializer<'c>) -> Result;
Lazy Value
that writes to Serializer
It's more ergonomic for closures used as lazy values to return type
implementing Serialize
, but sometimes that forces an allocation (eg.
String
s)
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.
#[macro_use] extern crate slog; use slog::{PushFnValue, Logger, Discard}; fn main() { // Create a logger with a key-value printing // `file:line` string value for every logging statement. // `Discard` `Drain` used for brevity. let root = Logger::root(Discard, o!( "source_location" => PushFnValue(|record , s| { s.serialize( format_args!( "{}:{}", record.file(), record.line(), ) ) }) )); }
Trait Implementations
impl<F> Value for PushFnValue<F> where
F: 'static + for<'c, 'd> Fn(&'c Record<'d>, PushFnValueSerializer<'c>) -> Result,
[src]
impl<F> Value for PushFnValue<F> where
F: 'static + for<'c, 'd> Fn(&'c Record<'d>, PushFnValueSerializer<'c>) -> Result,
Auto Trait Implementations
impl<F> Send for PushFnValue<F> where
F: Send,
impl<F> Send for PushFnValue<F> where
F: Send,
impl<F> Sync for PushFnValue<F> where
F: Sync,
impl<F> Sync for PushFnValue<F> where
F: Sync,