How to send a value to a Nickel Middleware function

Question

Consdier the following code:

extern crate nickel;
use nickel::{Nickel, HttpRouter, Request, Response, MiddlewareResult};

fn main() {
    let data = "wanted";
    let mut server = Nickel::new();
    server.get("/", landing);
    server.listen("localhost:6767");
}

fn landing<'a>(_: &mut Request, response: Response<'a>) -> MiddlewareResult<'a> {
    response.send("not wanted")
}

I want to use data in the function landing.

Answer 1

The Nickel examples show a way to pass a configuration into the server object.

Essentially, you instantiate a Nickel instance using its with_data method:

struct MyConfig {
    greet: String,
}

let my_config = MyConfig { greet: "hello".to_string() };

let mut server = Nickel::with_data(my_config);

And your handler can access it via the server_data method:

let my_config = req.server_data();
res.send(&*my_config.greet);

So, applying that to your specific example.. your code becomes:

extern crate nickel;
use nickel::{Nickel, HttpRouter, Request, Response, MiddlewareResult};

fn main() {
    let data = "wanted";
    let mut server = Nickel::with_data(data);
    server.get("/", landing);
    server.listen("localhost:6767");
}

fn landing<'a, 'mw>(request: &mut Request<&'a str>, response: Response<'mw, &'a str>) -> MiddlewareResult<'mw, &'a str> {
    response.send(*request.server_data())
}

Resulting in: