C++ API

Overview

Gazebo Fuel Tools lets you perform a set of operations over the resources hosted in any Gazebo Fuel server. These operations allow you to list all resources of a particular server, get the details of a resource or download it.

We're going to run a few examples, so let's start by creating a directory for this tutorial:

mkdir /tmp/fuel_tutorial && cd /tmp/fuel_tutorial

Download the files list.cc, details.cc, download.cc, CMakeLists.txt, and save them under /tmp/fuel_tutorial:

wget https://github.com/gazebosim/gz-fuel-tools/raw/gz-fuel-tools4/example/list.cc
wget https://github.com/gazebosim/gz-fuel-tools/raw/gz-fuel-tools4/example/details.cc
wget https://github.com/gazebosim/gz-fuel-tools/raw/gz-fuel-tools4/example/download.cc
wget https://github.com/gazebosim/gz-fuel-tools/raw/gz-fuel-tools4/example/CMakeLists.txt

Let's start by compiling the examples:

mkdir build && cd build
cmake ..
make

List resources from a Fuel server

Run the following example to see the list of models hosted in the default server:

./list -t model

You should see the name of the server followed by its list of models. Here's an example:

[https://fuel.gazebosim.org]
 
  Beer
  Wastebasket
  ambulance3
  ambulance2
  appartment3
  hammer
  another test model
  Test Model
  Bowl
  Cardboard Box
  Cessna C-172
  Fire station (collapsed)
  Beer
  Apartment
  Ambulance

Walkthrough

This example contains some boilerplate to parse command line arguments and load some configuration. Refer to the configuration tutorial for details about this part of the code. Let's focus on the relevant code for listing resources:

for (const auto &server : client.Config().Servers())
{
  std::cout << "[" << server.Url().Str() << "]\n\n";
  if (FLAGS_t == "model")
  {
    for (auto iter = client.Models(server); iter; ++iter)
      std::cout << "  " << iter->Identification().Name() << "\n";
  }
  else if (FLAGS_t == "world")
  {
    for (auto iter = client.Worlds(server); iter; ++iter)
      std::cout << "  " << iter->Name() << "\n";
  }
  std::cout << std::endl;
}

As you can see, we're iterating over the list of servers. For each server, we use the Models() or the Worlds() method to retrieve all the relevant resources from that server. Then, iterate over the resulting resources and print their names.

Get details of a resource

Run the following example to see the details of a model hosted in the default server:

./details -o caguero -n Beer -t model

You should see the details of the model. Here's an example:

Name: Beer
Owner: caguero
Version: 2
Description: A beer can
File size: 2969297
Upload date: 1516833583
Downloads: 1573
License name: Creative Commons - Attribution
License URL: http://creativecommons.org/licenses/by/4.0
License image URL: https://i.creativecommons.org/l/by/4.0/88x31.png
Server:
  URL: https://fuel.gazebosim.org
  Version: 1.0

Walkthrough

This example contains some boilerplate to parse command line arguments and load some configuration. Refer to the configuration tutorial for details about this part of the code. Let's focus on the relevant code for getting details of a resource:

// Fetch the details.
for (const auto &server : client.Config().Servers())
{
  if (FLAGS_t == "model")
  {
    // Set server
    auto id = modelIdentifier;
    id.SetServer(server);
 
    gz::fuel_tools::ModelIdentifier model;
    if (!client.ModelDetails(server, id, model))
      continue;
 
    std::cout << model.AsPrettyString() << std::endl;
  }
  else if (FLAGS_t == "world")
  {
    // Set server
    auto id = worldIdentifier;
    id.SetServer(server);
 
    gz::fuel_tools::WorldIdentifier world;
    if (!client.WorldDetails(id, world))
      continue;
 
    std::cout << world.AsPrettyString() << std::endl;
  }
}

As usual, we're iterating over the list of servers. For each server, we use the ModelDetails() or WorldDetails() methods to retrieve most of the properties of the resource. Then if the resource is retrieved successfully, we use the AsPrettyString() method to print its information to the screen.

Download a resource

Refer to the configuration tutorial to see an example of how to download resources programmatically.