:relfileprefix: ../../ [#boost-urls-param_view] = xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::param_view A query parameter == Synopsis Declared in header `` [source,cpp,subs="verbatim,macros,-callouts"] ---- struct param_view; ---- == Member Functions [cols=2,separator=¦] |=== ¦Name ¦Description ¦xref:boost/urls/param_view/2conversion.adoc[`operator param`] ¦ Conversion ¦xref:boost/urls/param_view/operator_ptr.adoc[`operator->`] ¦ ¦xref:boost/urls/param_view/2constructor.adoc[`param_view`] [.small]#[constructor]# ¦ Constructor |=== == Data Members [cols=2,separator=¦] |=== ¦Name ¦Description ¦xref:boost/urls/param_view/has_value.adoc[`has_value`] ¦ True if a value is present ¦xref:boost/urls/param_view/key.adoc[`key`] ¦ The key ¦xref:boost/urls/param_view/value.adoc[`value`] ¦ The value |=== == Description Objects of this type represent a single key and value pair in a query string where a key is always present and may be empty, while the presence of a value is indicated by xref:boost/urls/param_view/has_value.adoc[has_value] equal to true. An empty value is distinct from no value. Depending on where the object was obtained, the strings may or may not contain percent escapes. For most usages, key comparisons are case-sensitive and duplicate keys in a query are possible. However, it is the authority that has final control over how the query is interpreted. Keys and values in this object reference external character buffers. Ownership of the buffers is not transferred; the caller is responsible for ensuring that the assigned buffers remain valid until they are no longer referenced. === BNF [,cpp] ---- query-params = query-param *( "&" query-param ) query-param = key [ "=" value ] key = *qpchar value = *( qpchar / "=" ) ---- === Specification * link:https://en.wikipedia.org/wiki/Query_string[Query string (Wikipedia)] == See Also xref:boost/urls/param.adoc[param] , xref:boost/urls/param_pct_view.adoc[param_pct_view] .