在 `yield` 后抛出 `HTTPException` 或类似的异常是很诱人的，但是**这不起作用**。

带有`yield`的依赖中的退出代码在响应发送之后执行，因此[异常处理程序](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank}已经运行过。没有任何东西可以捕获退出代码（在`yield`之后）中的依赖抛出的异常。

所以，如果在`yield`之后抛出`HTTPException`，默认（或任何自定义）异常处理程序捕获`HTTPException`并返回HTTP 400响应的机制将不再能够捕获该异常。

这就是允许在依赖中设置的任何东西（例如数据库会话(DB session)）可以被后台任务使用的原因。

后台任务在响应发送之后运行。因此，无法触发`HTTPException`，因为甚至没有办法更改*已发送*的响应。

description. Overview Package Class Use Tree Deprecated Index Help PREV CLASS NEXT CLASS FRAMES NO FRAMES All Classes SUMMARY: NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD org/hamcrest/BaseMatcher.html Overview Package Class Use Tree Deprecated Index Help PREV CLASS NEXT CLASS FRAMES NO FRAMES All Classes SUMMARY: NESTED | FIELD | CONSTR | METHOD DETAIL: FIELD | CONSTR | METHOD org.hamcrest Class BaseMatcher<T> java.lang.Object org.hamcrest.BaseMatcher<T> All Implemented Interfaces: Matcher<T>,...

			mapValue[column] = nil
		}
	}
}

func (db *DB) scanIntoStruct(rows Rows, reflectValue reflect.Value, values []interface{}, fields []*schema.Field, joinFields [][]*schema.Field) {
	for idx, field := range fields {
		if field != nil {
			values[idx] = field.NewValuePool.Get()
		} else if len(fields) == 1 {
			if reflectValue.CanAddr() {
				values[idx] = reflectValue.Addr().Interface()
			} else {

          </association>
        </field>
      </fields>
    </class>
    <class>
      <name>Profile</name>
      <version>1.0.0</version>
      <description><![CDATA[
        Modifications to the build process which is keyed on some
        sort of environmental parameter.
      ]]></description>
      <fields>
        <field>
          <name>id</name>
          <required>true</required>

          </description>
        </field>
      </fields>
    </class>
    <!-- /BuildProfile support -->
    <class locationTracker="locations">
      <name>InputLocation</name>
      <version>2.0.0+</version>
      <fields>
        <!-- line, column and source fields are auto-generated by Modello -->
      </fields>
      <codeSegments>
        <codeSegment>

⚫️ 5️⃣📆 😋 🤚 `HTTPException` ⚖️ 🎏 🚪 📟, ⏮️ `yield`. ✋️ **⚫️ 🏆 🚫 👷**.

🚪 📟 🔗 ⏮️ `yield` 🛠️ *⏮️* 📨 📨, [⚠ 🐕‍🦺](../handling-errors.md#_4){.internal-link target=_blank} 🔜 ✔️ ⏪ 🏃. 📤 🕳 😽 ⚠ 🚮 👆 🔗 🚪 📟 (⏮️ `yield`).

, 🚥 👆 🤚 `HTTPException` ⏮️ `yield`, 🔢 (⚖️ 🙆 🛃) ⚠ 🐕‍🦺 👈 ✊ `HTTPException`Ⓜ & 📨 🇺🇸🔍 4️⃣0️⃣0️⃣ 📨 🏆 🚫 📤 ✊ 👈 ⚠ 🚫🔜.

👉 ⚫️❔ ✔ 🕳 ⚒ 🔗 (✅ 💽 🎉), 🖼, ⚙️ 🖥 📋.

    new_field.default = field.default  # type: ignore[misc]
    new_field.required = field.required  # type: ignore[misc]
    new_field.model_config = field.model_config  # type: ignore[attr-defined]
    new_field.field_info = field.field_info
    new_field.allow_none = field.allow_none  # type: ignore[attr-defined]
    new_field.validate_always = field.validate_always  # type: ignore[attr-defined]

# Dependencies with yield

FastAPI supports dependencies that do some <abbr title='sometimes also called "exit code", "cleanup code", "teardown code", "closing code", "context manager exit code", etc.'>extra steps after finishing</abbr>.

To do this, use `yield` instead of `return`, and write the extra steps (code) after.

!!! tip
    Make sure to use `yield` one single time.

!!! note "Technical Details"
    Any function that is valid to use with:

      <name>Metadata</name>
      <version>1.0.0+</version>
      <fields>
        <field xml.attribute="true" xml.tagName="modelVersion">
          <name>modelVersion</name>
          <version>1.1.0+</version>
          <type>String</type>
          <description>The version of the underlying metadata model.</description>
        </field>
        <field>
          <name>groupId</name>
          <version>1.0.0+</version>

            field.field_info.annotation
        ) and not isinstance(field.field_info, params.Body)

    def is_sequence_field(field: ModelField) -> bool:
        return field_annotation_is_sequence(field.field_info.annotation)

    def is_scalar_sequence_field(field: ModelField) -> bool:
        return field_annotation_is_scalar_sequence(field.field_info.annotation)