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RTI Connext Go Connector Examples

Building and running examples

$ go build $GOPATH/src/github.com/rticommunity/rticonnextdds-connector-go/examples/simple_reader/reader.go

After the go build command, you can find an executable for reader at your current path. Currently, the Go Connector links to the Connector C library dynamically so the path to the dynamic library needs to be added to your library path.

$ export LD_LIBRARY_PATH=$GOPATH/src/github.com/rticommunity/rticonnextdds-connector-go/rticonnextdds-connector/lib/x64Linux2.6gcc4.4.5:$LD_LIBRARY_PATH
$ ./reader

Example Overview

Import the Connector library

If you want to use the Go Connector, you have to import the package.

import "github.com/rticommunity/rticonnextdds-connector"

Instantiate a new connector

To create a new connector you have to pass a location of an XML configuration file and a configuration name in XML. For more information on the XML format check the XML App Creation guide or take a look at the ShapeExample.xml.

connector, err := rti.NewConnector("MyParticipantLibrary::Zero", filepath)

Delete a connector

To destroy all the DDS entities created by a connector, you should call the Delete().

connector, err := rti.NewConnector("MyParticipantLibrary::Zero", filepath)
...
...
connector.Delete()

Write a data sample

To write a data sample, you have to get a reference to the output port:

output, err := connector.GetOutput("MyPublisher::MySquareWriter")

then you have to set the fields in a sample instance:

output.Instance.SetInt("x", i)
output.Instance.SetInt("y", i*2)
output.Instance.SetInt("shapesize", 30)
output.Instance.SetString("color", "BLUE")

and then you can write:

output.Write();

Setting the fields in a sample instance:

The content of an instance can be set using a Go type that matches the original DDS type, or field by field:

  • Using a Go type with JSON encoding:
// Define a Go type for shape data
// Add an annotation (e.g. json:"color") that indicates an corresponding field in a DDS type
// The Set function uses the built-in encoding function for JSON
type Shape struct {
	Color     string `json:"color"`
	X         int    `json:"x"`
	Y         int    `json:"y"`
	Shapesize int    `json:"shapesize"`
}

var shape Shape
shape.Y = 2
output.Instance.Set(&shape)
  • Field by field:
output.Instance.SetInt("y", 2);

Nested fields can be accessed with the dot notation: "x.y.z", and array or sequences with square brakets: "x.y[1].z".

Reading/taking samples

To read/take samples first you have to get a reference to the input port:

input, err := connector.GetInput("MySubscriber::MySquareReader")

then you can call the Read() or Take() API:

input.Read();

or

input.Take();
  • Field by field: You can access each field individually like the example below. A Read() or Take() can return multiple samples. They are stored in an array. Every time you try to access a specific sample you have to specify an index (j in the example below).
input.Take()
numOfSamples := input.Samples.GetLength()
for j := 0; j < numOfSamples; j++ {
    if input.Infos.IsValid(j) {
        color := input.Samples.GetString(j, "color")
        x := input.Samples.GetInt(j, "x")
        y := input.Samples.GetInt(j, "y")
        shapesize := input.Samples.GetInt(j, "shapesize")

        log.Println("---Received Sample---")
        log.Printf("color: %s\n", color)
        log.Printf("x: %d\n", x)
        log.Printf("y: %d\n", y)
        log.Printf("shapesize: %d\n", shapesize)
}
  • Using a Go type with JSON decoding: You can access sample data in a deserialized Go type object.
// Define a Go type for shape data
// Add an annotation (e.g. json:"color") that indicates an corresponding field in a DDS type
// The Get function uses the built-in decoding function for JSON
type Shape struct {
        Color     string `json:"color"`
        X         int    `json:"x"`
        Y         int    `json:"y"`
        Shapesize int    `json:"shapesize"`
}

input.Take()
numOfSamples := input.Samples.GetLength()
for j := 0; j < numOfSamples; j++ {
    if input.Infos.IsValid(j) {
        var shape Shape
        err := input.Samples.Get(j, &shape)

        if err != nil {
            log.Println(err)
        }
        log.Println("---Received Sample---")
        log.Printf("color: %s\n", shape.Color)
        log.Printf("x: %d\n", shape.X)
        log.Printf("y: %d\n", shape.Y)
        log.Printf("shapesize: %d\n", shape.Shapesize)
}