[#boost-urls-param_view-2constructor]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/param_view.adoc[param_view]::param_view
:relfileprefix: ../../../
:mrdocs:


Constructor

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/param.hpp#L459[boost/url/param.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
xref:boost/urls/param_view/2constructor-07a.adoc[param_view]() = default;
----

[.small]#xref:boost/urls/param_view/2constructor-07a.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class OptionalString>
xref:boost/urls/param_view/2constructor-01.adoc[param_view](
    core::string_view key,
    OptionalString const& value) noexcept;
----

[.small]#xref:boost/urls/param_view/2constructor-01.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/param_view/2constructor-07e.adoc[param_view](xref:boost/urls/param.adoc[param] const& other) noexcept;
----

[.small]#xref:boost/urls/param_view/2constructor-07e.adoc[_» more..._]#

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/param_view/2constructor-03.adoc[param_view](
    core::string_view key_,
    core::string_view value_,
    bool has_value_) noexcept;
----

[.small]#xref:boost/urls/param_view/2constructor-03.adoc[_» more..._]#

== Description


Default constructed query parameters        have an empty key and no value.


=== Example

[,cpp]
----
param_view qp;
----

=== Postconditions

[,cpp]
----
this->key == "" && this->value == "" && this->has_value == false
----

=== Complexity

Constant.


=== Exception Safety

Throws nothing.



== Template Parameters


|===
| Name | Description

| *OptionalString*
| An optional string        type, such as `core::string_view`,        `std::nullptr`, xref:boost/urls/no_value_t.adoc[no_value_t], or        `optional<core::string_view>`.


|===

== Parameters


|===
| Name | Description

| *key,*
| value The key and value to set.


| *other*
| The param to reference


|===



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