<a href="#Switch_statements">"switch"</a> statements,
they can be used to declare local temporary variables.
</p>

<h3 id="Function_declarations">Function declarations</h3>

<!--
	Given the importance of functions, this section has always
	been woefully underdeveloped. Would be nice to expand this
	a bit.
-->

<p>
A function declaration binds an identifier, the <i>function name</i>,
to a function.

Pero primero, vamos a revisar algunos pequeños conceptos.

## ¿Con prisa? { #in-a-hurry }

Si no te importan ninguno de estos términos y solo necesitas agregar seguridad con autenticación basada en nombre de usuario y contraseña *ahora mismo*, salta a los siguientes capítulos.

## OAuth2 { #oauth2 }

	// Verify if region is valid.
	sRegion := cred.scope.region
	// Region is set to be empty, we use whatever was sent by the
	// request and proceed further. This is a work-around to address
	// an important problem for ListBuckets() getting signed with
	// different regions.
	if region == "" {
		region = sRegion
	}
	// Should validate region, only if region is set.
	if !isValidRegion(sRegion, region) {

```Python
q: Union[str, None] = None
```

Mais déclare explicitement `q` comme étant un paramètre de requête.

/// info

Gardez à l'esprit que la partie la plus importante pour rendre un paramètre optionnel est :

```Python
= None
```

ou :

```Python
= Query(None)
```

et utilisera ce `None` pour détecter que ce paramètre de requête **n'est pas requis**.

Usar uma URL relativa é importante para garantir que sua aplicação continue funcionando mesmo em um caso de uso avançado como [Atrás de um Proxy](../../advanced/behind-a-proxy.md){.internal-link target=_blank}.

///

Usar una URL relativa es importante para asegurarse de que tu aplicación siga funcionando incluso en un caso de uso avanzado como [Detrás de un Proxy](../../advanced/behind-a-proxy.md){.internal-link target=_blank}.

///

```

**Key Fields**: `crawlerContext`, `urlFilter`, `intervalController`, `clientFactory`, `ruleManager`

### CrawlerContext (`CrawlerContext.java`)

Execution context and configuration.

**Important Fields**:
```java
String sessionId                // Format: yyyyMMddHHmmssSSS
volatile CrawlerStatus status   // DONE, RUNNING
AtomicLong accessCount          // Thread-safe counter

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This package computes the exported API of a set of Go packages.
// It is only a test, not a command, nor a usefully importable package.

package main

import (
	"bufio"
	"bytes"
	"encoding/json"
	"fmt"
	"go/ast"
	"go/build"
	"go/parser"
	"go/token"
	"go/types"
	"internal/testenv"
	"io"
	"log"
	"os"

       * timeoutFuture.setException() calls run(). That reentrancy would already be harmless, since
       * timeoutFuture can be set (and delegate cancelled) only once. (And "set only once" is
       * important for other reasons: run() can still be invoked concurrently in different threads,
       * even with the above null checks.)
       */
      timeoutFutureRef = null;
      if (delegate.isDone()) {

```Python
callback_url = "https://example.com/api/v1/invoices/events/"
httpx.post(callback_url, json={"description": "Invoice paid", "paid": True})
```

Pero posiblemente la parte más importante del callback es asegurarse de que el usuario de tu API (el desarrollador externo) implemente la *API externa* correctamente, de acuerdo con los datos que *tu API* va a enviar en el request body del callback, etc.