# Dependencies

**FastAPI** has a very powerful but intuitive **<abbr title="also known as components, resources, providers, services, injectables">Dependency Injection</abbr>** system.

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection"

    assertThat(hpackReader!!.getAndResetHeaderList()).isEqualTo(headerBlock)
  }

  @Test
  fun literalHeaderFieldNeverIndexedIndexedName() {
    bytesIn.writeByte(0x14) // == Literal never indexed ==
    // Indexed name (idx = 4) -> :path
    bytesIn.writeByte(0x0c) // Literal value (len = 12)
    bytesIn.writeUtf8("/sample/path")
    hpackReader!!.readHeaders()

## Composition by architecture modules

Each [architecture module and platform](platforms.md) can contribute code to any of the runtimes.
Not every module contributes to every runtime.

The core-runtime module defines each runtime:

- The target JVM for the runtime. Each runtime has its own JVM compatibility constraints.

  optional k8s.io.apimachinery.pkg.apis.meta.v1.LabelSelector selector = 1;

  // An object that describes the pod that will be created.
  // The DaemonSet will create exactly one copy of this pod on every node
  // that matches the template's node selector (or on every node if no node
  // selector is specified).
  // More info: https://kubernetes.io/docs/concepts/workloads/controllers/replicationcontroller#pod-template

private
val dirVersionPattern = "\\d+\\.\\d+(\\.\\d+)?(-\\w+)*(-\\d{14}[+-]\\d{4})?".toRegex()


val logger = Logging.getLogger("gradlebuild.cleanup")


/**
 * Removes state for versions that we're unlikely to ever need again, such as old snapshot versions.
 */
fun FileSystemOperations.removeOldVersionsFromDir(dir: Directory, shouldDelete: Spec<GradleVersion>, dirPrefix: String = "", dirSuffix: String = "") {
    if (dir.asFile.isDirectory) {

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  }

  /**
   * Returns a new source that writes bytes to [cacheRequest] as they are read by the source
   * consumer. This is careful to discard bytes left over when the stream is closed; otherwise we
   * may never exhaust the source stream and therefore not complete the cached response.
   */
  @Throws(IOException::class)
  private fun cacheWritingResponse(
    cacheRequest: CacheRequest?,
    response: Response,

For large responses, returning a `Response` directly is much faster than returning a dictionary.

        // Continue" response before transmitting the request body. If we don't get that, return
        // what we did get (such as a 4xx response) without ever transmitting the request body.
        if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()
          responseBuilder = exchange.readResponseHeaders(expectContinue = true)

## CRUD utils

Now let's see the file `sql_app/crud.py`.

### Create all the CRUD utils

Create all the same CRUD utils as in the SQLAlchemy tutorial, all the code is very similar:

```Python hl_lines="1  4-5  8-9  12-13  16-20  23-24  27-30"
{!../../../docs_src/sql_databases_peewee/sql_app/crud.py!}
```

There are some differences with the code for the SQLAlchemy tutorial.