# Multipart - Crow
Introduced in: v0.2

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# Multipart

Introduced in: `v0.2`

Multipart is a way of forming HTTP requests or responses to contain multiple distinct parts.

Such an approach allows a request to contain multiple different pieces of data with potentially conflicting data types in a single response payload.
It is typically used either in HTML forms, or when uploading multiple files.

## How multipart messages work

The structure of a multipart request is typically consistent of:

- A Header: Typically `multipart/form-data;boundary=<boundary>`, This defines the HTTP message as being multipart, as well as defining the separator used to distinguish the different parts.
- 1 or more parts:
  - `--<boundary>`
  - Part header: typically `content-disposition: mime/type; name="<fieldname>"` (`mime/type` should be replaced with the actual mime-type), can also contain a `filename` property (separated from the rest by a `;` and structured similarly to the `name` property)
  - Value
- `--<boundary>--`

## Multipart messages in Crow

Crow supports multipart requests and responses though `crow::multipart::message`.
A message can be created either by defining the headers, boundary, and individual parts and using them to create the message. or simply by reading a `crow::request`.

Once a multipart message has been made, the individual parts can be accessed throughout `msg.parts`, `parts` is an `std::vector`.

Introduced in: `v1.0`

Part headers are organized in a similar way to request and response headers, and can be retrieved via `crow::multipart::get_header_object("header-key")`. This function returns a `crow::multipart::header` object.

The message's individual body parts can be accessed by name using `msg.get_part_by_name("part-name")`.

For more info on Multipart messages, go here