[#boost-urls-params_view]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::params&lowbar;view
:relfileprefix: ../../
:mrdocs:


A view representing query parameters in a URL

== Synopsis


Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_view.hpp#L47[boost&sol;url&sol;params&lowbar;view&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class params&lowbar;view
    : public xref:boost/urls/params_base.adoc[params&lowbar;base];
----

== Types

[cols=2]
|===
| Name | Description 

| xref:boost/urls/params_base/const_iterator.adoc[`const&lowbar;iterator`] 
| A Bidirectional iterator to a query parameter

| xref:boost/urls/params_base/const_reference.adoc[`const&lowbar;reference`] 
| The reference type

| xref:boost/urls/params_base/difference_type.adoc[`difference&lowbar;type`] 
| A signed integer type used to represent differences&period;

| xref:boost/urls/params_base/iterator.adoc[`iterator`] 
| A Bidirectional iterator to a query parameter

| xref:boost/urls/params_base/reference.adoc[`reference`] 
| The reference type

| xref:boost/urls/params_base/size_type.adoc[`size&lowbar;type`] 
| An unsigned integer type to represent sizes&period;

| xref:boost/urls/params_base/value_type.adoc[`value&lowbar;type`] 
| The value type

|===
== Member Functions

[cols=2]
|===
| Name | Description 

| xref:boost/urls/params_base/begin.adoc[`begin`] 
| Return an iterator to the beginning

| xref:boost/urls/params_base/buffer.adoc[`buffer`] 
| Return the referenced character buffer&period;

| xref:boost/urls/params_base/contains.adoc[`contains`] 
| Return true if a matching key exists

| xref:boost/urls/params_base/count.adoc[`count`] 
| Return the number of matching keys

| xref:boost/urls/params_base/empty.adoc[`empty`] 
| Return true if there are no params

| xref:boost/urls/params_base/end.adoc[`end`] 
| Return an iterator to the end

| xref:boost/urls/params_base/find.adoc[`find`] 
| Find a matching key


| xref:boost/urls/params_base/find_last.adoc[`find&lowbar;last`] 
| Find a matching key


| xref:boost/urls/params_view/operator_assign.adoc[`operator&equals;`] 
| Assignment

| xref:boost/urls/params_view/2constructor.adoc[`params&lowbar;view`]         [.small]#[constructor]#
| Constructor


| xref:boost/urls/params_base/size.adoc[`size`] 
| Return the number of params

|===
== Static Member Functions

[cols=2]
|===
| Name | Description 

| xref:boost/urls/params_base/max_size.adoc[`max&lowbar;size`] 
| Return the maximum number of characters possible

|===



== Description


Objects of this type are used to interpret    the query parameters as a bidirectional view    of key&sol;value pairs&period;

The view does not retain ownership of the    elements and instead references the original    character buffer&period; The caller is responsible    for ensuring that the lifetime of the buffer    extends until it is no longer referenced&period;


=== Example

[,cpp]
----
url_view u( "?first=John&last=Doe" );

params_view p = u.params();
----
Percent escapes in strings returned when    dereferencing iterators are automatically    decoded&period;


=== Iterator Invalidation

Changes to the underlying character buffer    can invalidate iterators which reference it&period;





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