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

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    use header::{EntityTag, IF_MATCH};

    header! {
        /// `If-Match` header, defined in
        /// [RFC7232](https://tools.ietf.org/html/rfc7232#section-3.1)
        ///
        /// The `If-Match` header field makes the request method conditional on
        /// the recipient origin server either having at least one current
        /// representation of the target resource, when the field-value is "*",
        /// or having a current representation of the target resource that has an
        /// entity-tag matching a member of the list of entity-tags provided in
        /// the field-value.
        ///
        /// An origin server MUST use the strong comparison function when
        /// comparing entity-tags for `If-Match`, since the client
        /// intends this precondition to prevent the method from being applied if
        /// there have been any changes to the representation data.
        ///
        /// # ABNF
        ///
        /// ```text
        /// If-Match = "*" / 1#entity-tag
        /// ```
        ///
        /// # Example values
        ///
        /// * `"xyzzy"`
        /// * "xyzzy", "r2d2xxxx", "c3piozzzz"
        ///
        /// # Examples
        ///
        /// ```rust
        /// use actix_web::HttpResponse;
        /// use actix_web::http::header::IfMatch;
        ///
        /// let mut builder = HttpResponse::Ok();
        /// builder.set(IfMatch::Any);
        /// ```
        ///
        /// ```rust
        /// use actix_web::HttpResponse;
        /// use actix_web::http::header::{IfMatch, EntityTag};
        ///
        /// let mut builder = HttpResponse::Ok();
        /// builder.set(
        ///     IfMatch::Items(vec![
        ///         EntityTag::new(false, "xyzzy".to_owned()),
        ///         EntityTag::new(false, "foobar".to_owned()),
        ///         EntityTag::new(false, "bazquux".to_owned()),
        ///     ])
        /// );
        /// ```
        (IfMatch, IF_MATCH) => {Any / (EntityTag)+}

        test_if_match {
            test_header!(
                test1,
                vec![b"\"xyzzy\""],
                Some(HeaderField::Items(
                    vec![EntityTag::new(false, "xyzzy".to_owned())])));
            test_header!(
                test2,
                vec![b"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""],
                Some(HeaderField::Items(
                    vec![EntityTag::new(false, "xyzzy".to_owned()),
                         EntityTag::new(false, "r2d2xxxx".to_owned()),
                         EntityTag::new(false, "c3piozzzz".to_owned())])));
            test_header!(test3, vec![b"*"], Some(IfMatch::Any));
        }
    }

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