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

Mutable encoded query parameter proxy

== Synopsis

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

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

== Description

This container exposes the percent‐encoded query parameters of a xref:boost/urls/url_base.adoc[`url_base`] as a bidirectional range while allowing mutation of the underlying URL. It references the URL’s buffer directly, so the url must stay alive for the lifetime of the proxy.

== Example

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

params_encoded_ref 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. Modifications made through the container invalidate some iterators to the underlying character buffer:

* xref:boost/urls/params_encoded_ref/append-09.adoc[`append`] : Only `end()`.
* xref:boost/urls/params_encoded_ref/assign-05.adoc[`assign`], xref:boost/urls/params_encoded_ref/clear.adoc[`clear`], `operator=` : All params.
* xref:boost/urls/params_encoded_ref/erase-03.adoc[`erase`] : Erased params and all params after (including `end()`).
* xref:boost/urls/params_encoded_ref/insert-0e.adoc[`insert`] : All params at or after the insertion point (including `end()`).
* xref:boost/urls/params_encoded_ref/replace-01.adoc[`replace`], xref:boost/urls/params_encoded_ref/set-06.adoc[`set`] : Modified params and all params after (including `end()`).

== Reads vs. writes

Even though this type can be used to mutate the referenced URL, this is still a proxy and every observer function inherited from xref:boost/urls/params_encoded_base.adoc[`params_encoded_base`] (for example xref:boost/urls/params_encoded_base/contains.adoc[`contains`], xref:boost/urls/params_encoded_base/find-0c.adoc[`find`], and xref:boost/urls/params_encoded_base/get_or.adoc[`get_or`]) behaves like the corresponding function on xref:boost/urls/params_encoded_view.adoc[`params_encoded_view`]: it inspects the current encoded query and does not perform any modifications.

== Base Classes

[cols="1,4"]
|===
|Name|Description

| `xref:boost/urls/params_encoded_base.adoc[params_encoded_base]`
| Percent‐encoded query helper base
|===

== Types

[cols="1,4"]
|===
| Name| Description
| xref:boost/urls/params_encoded_ref/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="1,4"]
|===
| Name| Description
| xref:boost/urls/params_encoded_ref/2constructor-01.adoc[`params_encoded_ref`]         [.small]#[constructor]#
| Constructor
| xref:boost/urls/params_encoded_ref/operator_assign-01.adoc[`operator=`] 
| Assignment
| xref:boost/urls/params_encoded_ref/append-09.adoc[`append`] 
| Append params
| xref:boost/urls/params_encoded_ref/assign-05.adoc[`assign`] 
| Assign params
| 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_ref/clear.adoc[`clear`] 
| Clear the contents of the container
| 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_ref/erase-03.adoc[`erase`] 
| Erase params
| 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/get_or.adoc[`get_or`] 
| Return the value for a key or a fallback
| xref:boost/urls/params_encoded_ref/insert-0e.adoc[`insert`] 
| Insert params
| xref:boost/urls/params_encoded_ref/replace-01.adoc[`replace`] 
| Replace params
| xref:boost/urls/params_encoded_ref/set-06.adoc[`set`] 
| Set a value
| xref:boost/urls/params_encoded_base/size.adoc[`size`] 
| Return the number of params
| xref:boost/urls/params_encoded_ref/unset.adoc[`unset`] 
| Remove the value on an element
| xref:boost/urls/params_encoded_ref/url.adoc[`url`] 
| Return the referenced url
| xref:boost/urls/params_encoded_ref/2conversion.adoc[`operator params_encoded_view`] 
| Conversion
|===

== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:boost/urls/params_encoded_base/max_size.adoc[`max_size`] 
| Return the maximum number of characters possible
|===

== Friends

[cols="1,4"]
|===
|Name|Description

| `xref:boost/urls/url_base.adoc[boost::urls::url_base]`
| Common functionality for containers
|===


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