# if_none_match.rs.html -- source
Source to the Rust file `src/header/common/if_none_match.rs`.
Keywords: rust, rustlang, rust-lang

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    use header::{EntityTag, IF_NONE_MATCH};

    header! {
        /// `If-None-Match` header, defined in
        /// [RFC7232](https://tools.ietf.org/html/rfc7232#section-3.2)
        ///
        /// The `If-None-Match` header field makes the request method conditional
        /// on a recipient cache or origin server either not having any current
        /// representation of the target resource, when the field-value is "*",
        /// or having a selected representation with an entity-tag that does not
        /// match any of those listed in the field-value.
        ///
        /// A recipient MUST use the weak comparison function when comparing
        /// entity-tags for If-None-Match (Section 2.3.2), since weak entity-tags
        /// can be used for cache validation even if there have been changes to
        /// the representation data.
        ///
        /// # ABNF
        ///
        /// ```text
        /// If-None-Match = "*" / 1#entity-tag
        /// ```
        ///
        /// # Example values
        ///
        /// * `"xyzzy"`
        /// * `W/"xyzzy"`
        /// * `"xyzzy", "r2d2xxxx", "c3piozzzz"`
        /// * `W/"xyzzy", W/"r2d2xxxx", W/"c3piozzzz"`
        /// * `*`
        ///
        /// # Examples
        ///
        /// ```rust
        /// use actix_web::HttpResponse;
        /// use actix_web::http::header::IfNoneMatch;
        ///
        /// let mut builder = HttpResponse::Ok();
        /// builder.set(IfNoneMatch::Any);
        /// ```
        ///
        /// ```rust
        /// use actix_web::HttpResponse;
        /// use actix_web::http::header::{IfNoneMatch, EntityTag};
        ///
        /// let mut builder = HttpResponse::Ok();
        /// builder.set(
        ///     IfNoneMatch::Items(vec![
        ///         EntityTag::new(false, "xyzzy".to_owned()),
        ///         EntityTag::new(false, "foobar".to_owned()),
        ///         EntityTag::new(false, "bazquux".to_owned()),
        ///     ])
        /// );
        /// ```
        (IfNoneMatch, IF_NONE_MATCH) => {Any / (EntityTag)+}

        test_if_none_match {
            test_header!(test1, vec![b"\"xyzzy\""]);
            test_header!(test2, vec![b"W/\"xyzzy\""]);
            test_header!(test3, vec![b"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""]);
            test_header!(test4, vec![b"W/\"xyzzy\", W/\"r2d2xxxx\", W/\"c3piozzzz\""]);
            test_header!(test5, vec![b"*"]);
        }
    }

    #[cfg(test)]
    mod tests {
        use super::IfNoneMatch;
        use header::{EntityTag, Header, IF_NONE_MATCH};
        use test::TestRequest;

        #[test]
        fn test_if_none_match() {
            let mut if_none_match: Result<IfNoneMatch, _>;

            let req = TestRequest::with_header(IF_NONE_MATCH, "*").finish();
            if_none_match = Header::parse(&req);
            assert_eq!(if_none_match.ok(), Some(IfNoneMatch::Any));

            let req =
                TestRequest::with_header(IF_NONE_MATCH, &b"\"foobar\", W/\"weak-etag\""[..])
                    .finish();

            if_none_match = Header::parse(&req);
            let mut entities: Vec<EntityTag> = Vec::new();
            let foobar_etag = EntityTag::new(false, "foobar".to_owned());
            let weak_etag = EntityTag::new(true, "weak-etag".to_owned());
            entities.push(foobar_etag);
            entities.push(weak_etag);
            assert_eq!(if_none_match.ok(), Some(IfNoneMatch::Items(entities)));
        }
    }

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