examples/celix-examples/services_example_cxx/README.md

---
title: Services Example C++
---

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# Intro

These examples show howto create and interact with services by example.

In both examples there is a provider and consumer bundle.
The provider bundle creates services and registers them to the Celix framework so that these services are available for use.
And the consumer bundle request the services from the Celix framework and uses them.

The examples use the `celix::BundleContext::registerService` to provide
services and uses a `celix::BundleContext::trackServices` to consume services.

The bundle context is the proxy to the Celix framework for a bundle
and can be used to:

- Register services
- Use services
- Track services
- Track bundles
- Track service trackers

See the `celix/BundleContext.h` for documentation about these - and other -functions

# Simple Service Provider & Consumer Example

The simple provider/consumer example can be executed by launching the
`SimpleServicesExample` executable target
(build in `${CMAKE_BUILD_DIR}/deploy/cxx_examples/SimpleServicesExample`)

In this example the provider bundle only register one calc service. And
the consumer bundle uses this service with use of a service tracker.

```ditaa
+----------------------+                  +------------------------+
|                      |                  |                        |
|                      |                  |                        |
|   SimpleProvider     | examples::ICalc  |    SimpleConsumer      |
|                      +--------O)--------+                        |
|       <bundle>       |                  |       <bundle>         |
|                      |                  |                        |
|                      |                  |                        |
+----------------------+                  +------------------------+
```

The effect of this can be examed by stopping and starting the provider/consumer bundles (respectively bundle id 3 & 4) using the interactive shell
to see how this works at runtime.
I.e. type `stop 3`, `stop 4`, `start 3`, `start 4` in different combinations.


# Dynamic Service Provider & Consumer Example

The dynamic provider/consumer example can be executed by launching the
`DynamicServicesExample` executable target
(build in `${CMAKE_BUILD_DIR}/deploy/cxx_examples/DynamicServicesExample`)

The dynamic service provide / consumer example show howto handle the dynamic behavior
of services. 

In this example the provider dynamically register more and less ICalc services in a thread.
The consumer create and destroy consumer for the ICalc services.

This example should give an idea how services can be safely used and tracked in a dynamic environment.