This can make it a lot easier for your users to **implement their APIs** to receive your **webhook** requests, they might even be able to autogenerate some of their own API code.

/// info

Webhooks are available in OpenAPI 3.1.0 and above, supported by FastAPI `0.99.0` and above.

///

## An app with webhooks

Note that the go_darwin_$GOARCH_exec wrapper uninstalls any existing app identified by
the bundle id before installing a new app. If the uninstalled app is the last app by
the developer identity, the device might also remove the permission to run apps from
that developer, and the exec wrapper will fail to install the new app. To avoid that,
install another app with the same developer identity but with a different bundle id.

So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:

```Python
something()
```

or

```Python
something(some_argument, some_keyword_argument="foo")
```

then it is a "callable".

## Classes as dependencies

You might notice that to create an instance of a Python class, you use that same syntax.

For example:

	if strings.Trim(sn, "0123456789") != "" {
		return time.Time{}, ErrHeader
	}
	if len(sn) < maxNanoSecondDigits {
		sn += strings.Repeat("0", maxNanoSecondDigits-len(sn)) // Right pad
	} else {
		sn = sn[:maxNanoSecondDigits] // Right truncate
	}
	nsecs, _ := strconv.ParseInt(sn, 10, 64) // Must succeed
	if len(ss) > 0 && ss[0] == '-' {
		return time.Unix(secs, -1*nsecs), nil // Negative correction
	}

  // http://docs.oracle.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html
  //  - Some providers may choose to also include alias names.
  //  - For example, the "SHA-1" algorithm might be referred to as "SHA1".
  //  - The algorithm name is not case-sensitive.
  private static final ImmutableMap<String, HashFunction> ALGORITHMS =
      new ImmutableMap.Builder<String, HashFunction>()

You can actually skip that extra header and it would still work.

But it's provided here to be compliant with the specifications.

Also, there might be tools that expect and use it (now or in the future) and that might be useful for you or your users, now or in the future.

That's the benefit of standards...

///

## See it in action

  private static final int MAX_BUSY_WAIT_SPINS = 1000;

  @Override
  public final void run() {
    /*
     * Set runner thread before checking isDone(). If we were to check isDone() first, the task
     * might be cancelled before we set the runner thread. That would make it impossible to
     * interrupt, yet it will still run, since interruptTask will leave the runner value null,
     * allowing the CAS below to succeed.
     */

allows for transforming your data to serve unique data format requirements for each application. For example, a dataset created by an ecommerce application might include personally identifiable information (PII). When the same data is processed for analytics, PII should be redacted. However, if the same dataset is used for a marketing campaign, you might need to enrich the data with additional details, such as information from the customer loyalty database.

MinIO's Object Lambda, enables application...

# Extending OpenAPI

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

## About "Form Fields"

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

**FastAPI** will make sure to read that data from the right place instead of JSON.

/// note | "Technical Details"

Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded`.