Services

You can create a ServiceClient using the Ros2 Singleton Here’s a short modified example of the service example provided in the Examples.

Button {
  property var serviceClient: Ros2.createServiceClient("/add_two_ints", "example_interfaces/srv/AddTwoInts")
  onClicked: {
    var result = serviceClient.sendRequestAsync(
      { a: 1, b: 3 },
      function (result) {
        textResult.text = !!result ? ("Result: " + result.sum) : "Failed"
      })
  }
}

In the first step, a service client is created. Here, the first argument is the service that is called and the second is the type of the service.

When the button is clicked, the service client is used to send a request with the first argument being the request and the second is a callback that is called once the service returns. The callback receives the result of the service call or the boolean value false if the call failed. The code will continue execution while the service call is processed, hence, if you want to prohibit concurrent calls to the same service, you’ll have to add your own logic to check whether a service call is currently active.

API

class ServiceClient : public QObjectRos2

Public Functions

ServiceClient(QString name, QString type)

Parameters:

• name – The service topic.

• type – The type of the service, e.g., “example_interfaces/srv/AddTwoInts”

bool isServiceReady() const

Returns whether the service is ready.

void sendRequestAsync(const QVariantMap &req, const QJSValue &callback)

Calls a service asynchronously returning immediately. Once the service call finishes, the optional callback is called with the result if provided.

Parameters:

• req – The service request, i.e., a filled request message of the service type.

• callback – The callback that is called once the service has finished. If the request failed, the callback is called with false.

Properties

bool ready

True if the ServiceClient is connected to the Service and the Service is ready, false otherwise.