Using //export in a file places a restriction on the preamble:
since it is copied into two different C output files, it must not
contain any definitions, only declarations. If a file contains both
definitions and declarations, then the two output files will produce
duplicate symbols and the linker will fail. To avoid this, definitions
must be placed in preambles in other files, or in C source files.

If you don't know, check the [Async: *"In a hurry?"*](../../async.md#in-a-hurry) section about `async` and `await` in the docs.

///

## Integrated with OpenAPI { #integrated-with-openapi }

All the request declarations, validations and requirements of your dependencies (and sub-dependencies) will be integrated in the same OpenAPI schema.

So, the interactive docs will have all the information from these dependencies too:

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:solid">main.py</u>
<span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting server
        Searching for package file structure
```

Result (German):

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:solid">main.py</u>

Esto en realidad inspiró la actualización de partes de Pydantic, para soportar el mismo estilo de declaración de validación (toda esta funcionalidad ya está disponible en Pydantic).

///

### [Hug](https://github.com/hugapi/hug) { #hug }

  /*
   * This class maintains a lazily-initialized table of atomically
   * updated variables, plus an extra "base" field. The table size
   * is a power of two. Indexing uses masked per-thread hash codes.
   * Nearly all declarations in this class are package-private,
   * accessed directly by subclasses.
   *
   * Table entries are of class Cell; a variant of AtomicLong padded
   * to reduce cache contention on most processors. Padding is

contents of the Program, including, for purposes of clarity any new file
in Source Code form that contains any contents of the Program. Modified
Works shall not include works that contain only declarations,
interfaces, types, classes, structures, or files of the Program solely
in each case in order to link to, bind by name, or subclass the Program
or Modified Works thereof.

```bash
# Eine Begrüßung an das Universum ausgeben
echo "Hello universe"
```

... und ein Konsolen-Codebeispiel ...

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:solid">main.py</u>
<span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting server
        Searching for package file structure
```

... und noch ein Konsolen-Codebeispiel ...

**FastAPI** takes advantage of these type hints to do several things.

With **FastAPI** you declare parameters with type hints and you get:

* **Editor support**.
* **Type checks**.

...and **FastAPI** uses the same declarations to:

* **Define requirements**: from request path parameters, query parameters, headers, bodies, dependencies, etc.
* **Convert data**: from the request to the required type.
* **Validate data**: coming from each request:

    @SuppressWarnings("nullness")
    Object[] result = ObjectArrays.toArrayImpl(this);
    return result;
  }

  @Override
  @SuppressWarnings("nullness") // b/192354773 in our checker affects toArray declarations
  public <T extends @Nullable Object> T[] toArray(T[] other) {
    return ObjectArrays.toArrayImpl(this, other);
  }

  @Override
  public boolean contains(@Nullable Object object) {
    try {

Bir Bash code örneği...

```bash
# Evrene bir selam yazdır
echo "Hello universe"
```

...ve bir console code örneği...

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:solid">main.py</u>
<span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting server
        Searching for package file structure
```

...ve bir başka console code örneği...