[#SER_PARAMS]
= SER_PARAMS
:mrdocs:

Formatter methods can retrieve parameters attached to a stream using the SER_PARAMS(type) macro as long as the stream is created directly or indirectly with a parameter of that type. This permits making serialization depend on run‐time context in a type‐safe way.

== Synopsis

Declared in `<serialize.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define SER_PARAMS(type)

----

== Description

Example use: struct BarParameter { bool fancy; ... }; struct Bar { ... }; struct FooFormatter { FORMATTER_METHODS(Bar, obj) { auto& param = SER_PARAMS(BarParameter); if (param.fancy) { READWRITE(VARINT(obj.value)); } else { READWRITE(obj.value); } } }; which would then be invoked as READWRITE(BarParameter{...}(Using<FooFormatter>(obj.foo)))

parameter(obj) can be invoked anywhere in the call stack; it is passed down recursively into all serialization code, until another serialization parameter overrides it.

Parameters will be implicitly converted where appropriate. This means that "parent" serialization code can use a parameter that derives from, or is convertible to, a "child" formatter's parameter type.

Compilation will fail in any context where serialization is invoked but no parameter of a type convertible to BarParameter is provided.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *type*
| The parameter type to retrieve from the stream.
|===


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