### Dependency Injection { #dependency-injection }

FastAPI includes an extremely easy to use, but extremely powerful <abbr title='also known as "components", "resources", "services", "providers"'><strong>Dependency Injection</strong></abbr> system.

* Even dependencies can have dependencies, creating a hierarchy or **"graph" of dependencies**.
* All **automatically handled** by the framework.

### Dependency injection

FastAPI'ın inanılmaz derecede kullanımı kolay, fakat inanılmaz derecede güçlü <abbr title='"components", "resources", "services", "providers" olarak da bilinen'><strong>Dependency Injection </strong></abbr> sistemi var.

* Dependencylerin bile dependencies'i olabiliyor, FastAPI bunun  için **graph of "dependency"** yaratıyor.

                return Stream.empty();
            }
        };
    }

    /**
     * Creates new instance of problem collector with configuration from the provided session.
     *
     * @param <P> the type of problem
     * @param protoSession the session containing configuration for the problem collector
     * @return a new problem collector instance
     */
    @Nonnull

        @DisplayName("should execute strategies in priority order")
        void shouldExecuteStrategiesInPriorityOrder() throws Exception {
            // This test verifies that strategies are executed in the order they are provided
            // The actual priority ordering is handled by dependency injection
            UpgradeContext context = createMockContext();
            Map<Path, Document> pomMap = Map.of(Paths.get("pom.xml"), mock(Document.class));

	errFunctionNotImplemented = errors.New("Function is not yet implemented")
	errUnexpectedInvalidNode  = errors.New("Unexpected node value")
	errInvalidKeypath         = errors.New("A provided keypath is invalid")
)

// qProp contains analysis info about an SQL term.
type qProp struct {
	isAggregation, isRowFunc bool

	err error
}

// `combine` combines a pair of `qProp`s, so that errors are

 *
 * <p>The analyzer processes POM files recursively, tracking string occurrences and their locations within the POM structure.
 * It can identify areas where string deduplication could provide significant memory savings.</p>
 *
 * <p>Usage example:</p>
 * <pre>
 * PomMemoryAnalyzer analyzer = new PomMemoryAnalyzer();
 * Model model = reader.read(Files.newInputStream(pomPath));
 * analyzer.analyzePom(model);

加上来自 Starlette（包括 **session cookie**）的所有安全特性。

所有的这些都是可复用的工具和组件，可以轻松与你的系统，数据仓库，关系型以及 NoSQL 数据库等等集成。



### 依赖注入

FastAPI 有一个使用非常简单，但是非常强大的<abbr title='也叫做 "components", "resources", "services", "providers"'><strong>依赖注入</strong></abbr>系统。

* 甚至依赖也可以有依赖，创建一个层级或者**“图”依赖**。
* 所有**自动化处理**都由框架完成。
* 所有的依赖关系都可以从请求中获取数据，并且**增加了路径操作**约束和自动文档生成。
* 即使在依赖项中被定义的*路径操作* 也会**自动验证**。
* 支持复杂的用户身份认证系统，**数据库连接**等等。

	// more than one disk returned an error.
	// Will not be called if everything operates as expected.
	finished func(errs []error)
}

// listPathRaw will list a path on the provided drives.
// See listPathRawOptions on how results are delivered.
// Directories are always returned.
// Cache will be bypassed.
// Context cancellation will be respected but may take a while to effectuate.

enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and
[permitted by the Go 1 compatibility rules](/doc/go1compat).
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair

	return TrimRightFunc(TrimLeftFunc(s, f), f)
}

// TrimPrefix returns s without the provided leading prefix string.
// If s doesn't start with prefix, s is returned unchanged.
func TrimPrefix(s, prefix []byte) []byte {
	if HasPrefix(s, prefix) {
		return s[len(prefix):]
	}
	return s
}

// TrimSuffix returns s without the provided trailing suffix string.
// If s doesn't end with suffix, s is returned unchanged.