CODEWITHSUNDEEP
rust
Hokutosei
Hokutosei

Reputation: 2164

How do I send an interpolated string on a channel?

How do I store a variable in a string? I've read the examples, but they are all just println!().

//javascript
var url_str = "http://api.weather/city" + city_code + "/get";

//go
urlStr := fmt.Sprintf("http://api.weather/%s/get", cityCode)

// Edit: Rust 
let url_str = format!("http://api.openweathermap.org/data/2.5/weather?q={}", city_code);

I am using tx.send() and want to send an interpolated string on the channel like this:

let url_str = "http://api.weather";
c.send(url_str);

but I get an error

src/http_get/http_getter.rs:21:17: 21:24 error: `url_str` does not live long enough
src/http_get/http_getter.rs:21         c.send(&url_str);
                                           ^~~~~~~

Here is the function that I am trying to implement for constructing the URL:

pub fn construct_url(c: &Sender<String>, city_code: &str) {
        let url_str = format!("http://api.openweathermap.org/data/2.5/weather?q={}", city_code);
        println!("{}", url_str);
        c.send(url_str);
}

Upvotes: 2

Views: 756

Answers (1)

Chris Morgan
Chris Morgan

Reputation: 90852

With elided lifetimes and types reinstated, here’s what you have:

pub fn construct_url<'a, 'b, 'c>(c: &'a Sender<&'b str>, city_code: &'c str) {
    let url_str: String = format!("http://api.openweathermap.org/data/2.5/weather?q={}", city_code);
    println!("{}", url_str);
    c.send(&url_str);
}

Bear in mind the distinctions between String and &str: &str is a string slice, a reference to a string that someone else owns; String is the owned variety.

'b is necessarily at least as long as the entire function body—any string you construct inside the function will not live long enough for 'b. Therefore your sender will need to send a String, not a &str.

pub fn construct_url(c: &Sender<String>, city_code: &str) {
    let url_str = format!("http://api.openweathermap.org/data/2.5/weather?q={}", city_code);
    println!("{}", url_str);
    c.send(url_str);
}

Upvotes: 4

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