Struct fern::FormatCallback

#[must_use = "format callback must be used for log to process correctly"]
pub struct FormatCallback<'a>(_);

Callback struct for use within a formatter closure

Callbacks are used for formatting in order to allow usage of std::fmt-based formatting without the allocation of the formatted result which would be required to return it.

Example usage:

fern::Dispatch::new()
    .format(|callback: fern::FormatCallback, message, record| {
        callback.finish(format_args!("[{}] {}", record.level(), message))
    })

Methods

impl<'a> FormatCallback<'a>

fn finish(self, formatted_message: Arguments)

Complete the formatting call that this FormatCallback was created for.

This will call the rest of the logging chain using the given formatted message as the new payload message.

Example usage:

callback.finish(format_args!("[{}] {}", record.level(), message))

See format_args!.