mouse--a mouse--O mouse!'  The Mouse looked at her rather
inquisitively, and seemed to her to wink with one of its little
eyes, but it said nothing.

  `Perhaps it doesn't understand English,' thought Alice; `I
daresay it's a French mouse, come over with William the
Conqueror.'  (For, with all her knowledge of history, Alice had
no very clear notion how long ago anything had happened.)  So she

   * Integer#decode} and {@link Integer#toString()}. The returned converter throws {@link
   * NumberFormatException} if the input string is invalid.
   *
   * <p><b>Warning:</b> please see {@link Integer#decode} to understand exactly how strings are
   * parsed. For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the
   * value {@code 83}.
   *
   * @since 16.0
   */

To understand more about it, see the section [Benchmarks](https://fastapi.tiangolo.com/benchmarks/).

## Dependencies { #dependencies }

FastAPI depends on Pydantic and Starlette.

这在 Pydantic 2 或更高版本中可用。😎

///

/// tip | 提示

如果你需要进行任何需要与**外部组件**通信的校验，例如数据库或其他 API，你应该改用 **FastAPI 依赖项**，稍后你会学到它们。

这些自定义校验器用于只需检查请求中**同一份数据**即可完成的事情。

///

### 理解这段代码 { #understand-that-code }

关键点仅仅是：在 `Annotated` 中使用带函数的 **`AfterValidator`**。不感兴趣可以跳过这一节。🤸

---

但如果你对这个具体示例好奇，并且还愿意继续看，这里有一些额外细节。

#### 字符串与 `value.startswith()` { #string-with-value-startswith }

mouse--a mouse--O mouse!'  The Mouse looked at her rather
inquisitively, and seemed to her to wink with one of its little
eyes, but it said nothing.

  `Perhaps it doesn't understand English,' thought Alice; `I
daresay it's a French mouse, come over with William the
Conqueror.'  (For, with all her knowledge of history, Alice had
no very clear notion how long ago anything had happened.)  So she

they need to be linked into the final binary, along with the libraries
they might depend on (in the case of puts, stdio). cmd/link has been
extended to understand basic ELF files, but it does not understand ELF
in the full complexity that modern C libraries embrace, so it cannot
in general generate direct references to the system libraries.

such as those in the <a href="/pkg/sync/"><code>sync</code></a>
and <a href="/pkg/sync/atomic/"><code>sync/atomic</code></a> packages.
</p>

<p>
If you must read the rest of this document to understand the behavior of your program,
you are being too clever.
</p>

<p>
Don't be clever.
</p>

<h3 id="overview">Informal Overview</h3>

<p>

 *   <li>{@link #min} / {@link #max}
 * </ul>
 *
 * <h3>Understanding complex orderings</h3>
 *
 * <p>Complex chained orderings like the following example can be challenging to understand.
 *
 * {@snippet :
 * Ordering<Foo> ordering =
 *     Ordering.natural()
 *         .nullsFirst()
 *         .onResultOf(getBarFunction)
 *         .nullsLast();
 * }
 *

   * Long#decode} and {@link Long#toString()}. The returned converter throws {@link
   * NumberFormatException} if the input string is invalid.
   *
   * <p><b>Warning:</b> please see {@link Long#decode} to understand exactly how strings are parsed.
   * For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the value
   * {@code 83L}.
   *
   * @since 16.0
   */

 *   <li>{@link #min} / {@link #max}
 * </ul>
 *
 * <h3>Understanding complex orderings</h3>
 *
 * <p>Complex chained orderings like the following example can be challenging to understand.
 *
 * {@snippet :
 * Ordering<Foo> ordering =
 *     Ordering.natural()
 *         .nullsFirst()
 *         .onResultOf(getBarFunction)
 *         .nullsLast();
 * }
 *