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kotlinlang

is there any Interceptor equivalent in Ktor like OkHttp?

When configuring Ktor `HttpClient` with the OkHttp engine, you have the opportunity to configure OkHttp to use interceptors.

I haven't used OkHttp, but I assume interceptor is something like a ktor client feature that can intercept calls at various stages

By inspecting the `JsonFeature`, I noticed that it is possible to define interceptors with the following syntax :
```
// Transformation on the request
httpClient.requestPipeline.intercept(HttpRequestPipeline.Transform) { playload -&gt;
    // Do some things with the request, then send it to the next level
    val result = transformMyRequest(payload)
    proceedWith(result)
}

// Transformations on the response
httpClient.responsePipeline.intercept(HttpResponsePipeline.Transform) { (info, body) -&gt;
    // Do some things with the response, then send it to the next level
    val result = transformMyResponse(info, body)
    proceedWith(result)
}
```
More details on Ktor Pipelining : <https://ktor.io/advanced/pipeline.html#interceptors-and-the-pipelinecontext>

You can also use this to install an `interceptor`:

```
 private fun HttpClientConfig&lt;*&gt;.authenticatedRequestsEngine() {
        engine {
            this@authenticatedRequestsEngine.install(KEY_AUTH_INTERCEPTOR) {
                this@authenticatedRequestsEngine.defaultRequest {
                    parameter(KEY_API_SECRET, BuildKonfig.API_KEY)
                }
            }
        }
    }
```

I use it to authenticate each request by adding a `parameter` with an `API_KEY`

<https://api.ktor.io/0.9.4/io.ktor.client/-http-client-config/install.html>

`Installs an interceptor defined by block. The key parameter is used as a unique name, that also prevents installing duplicated interceptors.`