Writer

Writer is used to write content into Response:

#[async_trait]
pub trait Writer {
    async fn write(mut self, req: &mut Request, depot: &mut Depot, res: &mut Response);
}

Compared to Handler:

#[async_trait]
pub trait Handler: Send + Sync + 'static {
    async fn handle(&self, req: &mut Request, depot: &mut Depot, res: &mut Response, ctrl: &mut FlowCtrl);
}

The main differences between them are:

Different purposes: Writer represents writing specific content into Response, implemented by concrete content such as strings, error messages, etc. In contrast, Handler is used to process the entire request.
Writer is created within a Handler and consumes itself when the write function is called, making it a one-time call. On the other hand, Handler is shared across all requests.
Writer can be returned as the content in the Result of a Handler.
Writer does not include a FlowCtrl parameter, so it cannot control the execution flow of the entire request.

Scribe implements Writer but offers fewer capabilities compared to Writer:

pub trait Scribe {
    fn render(self, res: &mut Response);
}

The rendering function of Scribe only writes data into Response and cannot retrieve information from Request or Depot during this process.

#Writer

Writer