frankmeza
2/16/2019 - 8:17 AM

A Rust Client using Reqwest and dotenv #rust

A Rust Client using Reqwest and dotenv #rust

rust_client_coinmarketcap.md
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Rust Client using Reqwest

extern crate dotenv;
    extern crate hyper;

    use http::header::{HeaderName, HeaderValue};
    use reqwest::{Client, Method, Url};

    fn get_env_vars() -> (HeaderName, HeaderValue, Url) {
        // use dotenv to pull the values from .env
        let cmc_api_key = dotenv::var("CMC_API_KEY").expect("CMC_API_KEY not found");
        let cmc_api_endpoint = dotenv::var("CMC_API_ENDPOINT").expect("CMC_API_ENDPOINT not found");
        let cmc_header_name = dotenv::var("CMC_HEADER_NAME").expect("CMC_HEADER_NAME not found");

        // parse and unwrap the values
        let header_name = cmc_header_name.parse::<HeaderName>().unwrap();
        let header_value = cmc_api_key.parse::<HeaderValue>().unwrap();
        let url: Url = cmc_api_endpoint.parse().unwrap();

        // return a tuple of the values
        (header_name, header_value, url)
    }

    fn fetch_cmc_data(name: HeaderName, value: HeaderValue, url: Url) -> reqwest::Response {
        let client = Client::new();

        let request = client
            .request(Method::GET, url)
            .header(name, value)
            .build()
            .unwrap();

        client.execute(request).unwrap()
    }

    fn main() {
        let (header_name, header_value, url) = get_env_vars();
        let mut response = fetch_cmc_data(header_name, header_value, url);

        println!("{:?}", response.text());
    }

This is a Rust client using the libraries reqwest and dotenv . It calls an API endpoint at coinmarketcap.com and returns a list of cryptocurrencies, the first 60+ lines are found at the bottom of this post.

  1. starting from fn main(), a tuple of the header_name, header_value, and url are returned from get_env_vars()
  2. get_env_vars() pulls the values from a .env file in the same directory
  3. the contents of the tuple are passed into fn fetch_cmc_data() , which then returns reqwest::Response into mut response .
    • a reqwest::Client is instantiated first
    • a reqwest::RequestBuilder receives the url in request() , and the header name and value are passed into header()
    • .build() and .unwrap() are called immediately to create a reqwest::Request
    • client now executes the request, and calls unwrap() , but you should handle a client error here
  4. text() output from mut response is fed into a printing function. Boom!

Response

This is the first part of the response from the above client request:

{
    "status":  {
        "timestamp":  "2019-02-16T08: 28: 15.822Z",
        "error_code":  0,
        "error_message":  null,
        "elapsed":  14,
        "credit_count":  1    
    },
    "data":  [
        {
            "id":  1,
            "name":  "Bitcoin",
            "symbol":  "BTC",
            "slug":  "bitcoin",
            "circulating_supply":  17540550,
            "total_supply":  17540550,
            "max_supply":  21000000,
            "date_added":  "2013-04-28T00: 00: 00.000Z",
            "num_market_pairs":  6653,
            "tags":  [
                "mineable"            
            ],
            "platform":  null,
                "cmc_rank":  1,
                "last_updated":  "2019-02-16T08: 27: 28.000Z",
                "quote":  {
                    "USD":  {
                            "price":  3635.49176252,
                            "volume_24h":  6060386037.82371,
                            "percent_change_1h":  0.0488409,
                            "percent_change_24h":  0.14031,
                            "percent_change_7d":  -0.810947,
                            "market_cap":  63768525035.07019,
                            "last_updated":  "2019-02-16T08: 27: 28.000Z"                
                    }            
                }        
        },
        {
                "id":  1027,
                "name":  "Ethereum",
                "symbol":  "ETH",
                "slug":  "ethereum",
                "circulating_supply":  104879559.8741,
                "total_supply":  104879559.8741,
                "max_supply":  null,
                "date_added":  "2015-08-07T00: 00: 00.000Z",
                "num_market_pairs":  4759,
                "tags":  [
                    "mineable"            
                ],
                "platform":  null,
                "cmc_rank":  2,
                "last_updated":  "2019-02-16T08: 27: 19.000Z",
                "quote":  {
                    "USD":  {
                            "price":  123.164946188,
                            "volume_24h":  2964473039.45236,
                            "percent_change_1h":  0.0820388,
                            "percent_change_24h":  0.194405,
                            "percent_change_7d":  3.483,
                            "market_cap":  12917485348.11465,
                            "last_updated":  "2019-02-16T08: 27: 19.000Z"                
                    }            
                }        
        },
...