[#boost-urls-params_encoded_view]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::params_encoded_view
:relfileprefix: ../../
:mrdocs:

A view representing query parameters in a URL

== Synopsis

Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_encoded_view.hpp#L58[boost/url/params_encoded_view.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class params_encoded_view
    : public xref:boost/urls/params_encoded_base.adoc[params_encoded_base];
----

== Base Classes

[cols=2]
|===
| Name
| Description
| `xref:boost/urls/params_encoded_base.adoc[params_encoded_base]`
| Common functionality for containers
|===

== Types

[cols=2]
|===
| Name
| Description
| xref:boost/urls/params_encoded_base/iterator.adoc[`iterator`] 
| A Bidirectional iterator to a query parameter
| xref:boost/urls/params_encoded_base/const_iterator.adoc[`const_iterator`] 
| A Bidirectional iterator to a query parameter
| xref:boost/urls/params_encoded_base/const_reference.adoc[`const_reference`] 
| The reference type
| xref:boost/urls/params_encoded_base/difference_type.adoc[`difference_type`] 
| A signed integer type used to represent differences.
| xref:boost/urls/params_encoded_base/reference.adoc[`reference`] 
| The reference type
| xref:boost/urls/params_encoded_base/size_type.adoc[`size_type`] 
| An unsigned integer type to represent sizes.
| xref:boost/urls/params_encoded_base/value_type.adoc[`value_type`] 
| The value type
|===

== Member Functions

[cols=2]
|===
| Name
| Description
| xref:boost/urls/params_encoded_view/2constructor-0b.adoc[`params_encoded_view`]         [.small]#[constructor]#
| Constructor
| xref:boost/urls/params_encoded_view/operator_assign.adoc[`operator=`] 
| Assignment
| xref:boost/urls/params_encoded_base/begin.adoc[`begin`] 
| Return an iterator to the beginning
| xref:boost/urls/params_encoded_base/buffer.adoc[`buffer`] 
| Return the query corresponding to these params
| xref:boost/urls/params_encoded_base/contains.adoc[`contains`] 
| Return true if a matching key exists
| xref:boost/urls/params_encoded_base/count.adoc[`count`] 
| Return the number of matching keys
| xref:boost/urls/params_encoded_base/empty.adoc[`empty`] 
| Return true if there are no params
| xref:boost/urls/params_encoded_base/end.adoc[`end`] 
| Return an iterator to the end
| xref:boost/urls/params_encoded_base/find-0c.adoc[`find`] 
| Find a matching key
| xref:boost/urls/params_encoded_base/find_last-0b.adoc[`find_last`] 
| Find a matching key
| xref:boost/urls/params_encoded_base/size.adoc[`size`] 
| Return the number of params
| xref:boost/urls/params_encoded_view/2conversion.adoc[`operator params_view`] 
| Conversion
|===

== Static Member Functions

[cols=2]
|===
| Name
| Description
| xref:boost/urls/params_encoded_base/max_size.adoc[`max_size`] 
| Return the maximum number of characters possible
|===

== Friends

[cols=2]
|===
| Name
| Description
| `xref:boost/urls/parse_query.adoc[parse_query]`
| Parse a string and return an encoded params view
| `query_rule_t`
| 
| `xref:boost/urls/params_encoded_ref.adoc[params_encoded_ref]`
| A view representing query parameters in a URL
| `xref:boost/urls/params_view.adoc[params_view]`
| A view representing query parameters in a URL
| `xref:boost/urls/url_view_base.adoc[url_view_base]`
| Common functionality for containers
| `xref:boost/urls/parse_query.adoc[parse_query]`
| Parse a string and return an encoded params view
| `query_rule_t`
| 
| `xref:boost/urls/params_encoded_ref.adoc[params_encoded_ref]`
| A view representing query parameters in a URL
| `xref:boost/urls/params_view.adoc[params_view]`
| A view representing query parameters in a URL
| `xref:boost/urls/url_view_base.adoc[url_view_base]`
| Common functionality for containers
| `xref:boost/urls/parse_query.adoc[parse_query]`
| Parse a string and return an encoded params view
| `query_rule_t`
| 
| `xref:boost/urls/params_encoded_ref.adoc[params_encoded_ref]`
| A view representing query parameters in a URL
| `xref:boost/urls/params_view.adoc[params_view]`
| A view representing query parameters in a URL
| `xref:boost/urls/url_view_base.adoc[url_view_base]`
| Common functionality for containers
|===

== Description

Objects of this type are used to interpret the query parameters as a bidirectional view of key/value pairs.

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

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

params_encoded_view p = u.encoded_params();
----
Strings produced when elements are returned have type xref:boost/urls/param_pct_view.adoc[`param_pct_view`] and represent encoded strings. Strings passed to member functions may contain percent escapes, and throw exceptions on invalid inputs.

== Iterator Invalidation
Changes to the underlying character buffer can invalidate iterators which reference it.


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