机器人编程趣味实践04-逻辑判断（if）
【摘要】 在上一节中，介绍了简单的运算规则。核心代码如下：
服务端：
RCLCPP_INFO( g_node->get_logger(), "分别获取两个整数 %" PRId64 " + %" PRId64, request->a, request->b); response->sum = request->a + request->b; ...
在上一节中，介绍了简单的运算规则。核心代码如下：
服务端：
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RCLCPP_INFO( g_node->get_logger(),
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"分别获取两个整数 %" PRId64 " + %" PRId64, request->a, request->b);
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response->sum = request->a + request->b;
当然，+可以更换为其他运算。
客户端：
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RCLCPP_INFO(
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node->get_logger(), "结果 %" PRId64 " + %" PRId64 " = %" PRId64,
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request->a, request->b, result->sum);
这里的结果是由服务端发送给客户端的，这是一个简单的运算调用案例。
在实际运行中，由于使用中文字符，出现了乱码的情况，后续将以英文字符为主，毕竟国外开源代码几乎都是全英文的嘛。
最初，介绍了基本的消息传递，然后是运算，本节将重点关注逻辑判断，如if。
黄金分割与斐波那契数列
先上程序
服务器端：
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#include <inttypes.h>
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#include <memory>
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#include "example_interfaces/action/fibonacci.hpp"
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#include "rclcpp/rclcpp.hpp"
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// TODO(jacobperron): Remove this once it is included as part of 'rclcpp.hpp'
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#include "rclcpp_action/rclcpp_action.hpp"
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class MinimalActionServer : public rclcpp::Node
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{
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public:
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using Fibonacci = example_interfaces::action::Fibonacci;
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using GoalHandleFibonacci = rclcpp_action::ServerGoalHandle<Fibonacci>;
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explicit MinimalActionServer(const rclcpp::NodeOptions & options = rclcpp::NodeOptions())
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: Node("minimal_action_server", options)
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{
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using namespace std::placeholders;
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this->action_server_ = rclcpp_action::create_server<Fibonacci>(
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this->get_node_base_interface(),
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this->get_node_clock_interface(),
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this->get_node_logging_interface(),
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this->get_node_waitables_interface(),
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"fibonacci",
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std::bind(&MinimalActionServer::handle_goal, this, _1, _2),
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std::bind(&MinimalActionServer::handle_cancel, this, _1),
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std::bind(&MinimalActionServer::handle_accepted, this, _1));
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}
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private:
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rclcpp_action::Server<Fibonacci>::SharedPtr action_server_;
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rclcpp_action::GoalResponse handle_goal(
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const rclcpp_action::GoalUUID & uuid,
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std::shared_ptr<const Fibonacci::Goal> goal)
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{
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RCLCPP_INFO(this->get_logger(), "Received goal request with order %d", goal->order);
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(void)uuid;
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// Let's reject sequences that are over 9000
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if (goal->order > 9000) {
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return rclcpp_action::GoalResponse::REJECT;
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}
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return rclcpp_action::GoalResponse::ACCEPT_AND_EXECUTE;
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}
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rclcpp_action::CancelResponse handle_cancel(
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const std::shared_ptr<GoalHandleFibonacci> goal_handle)
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{
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RCLCPP_INFO(this->get_logger(), "Received request to cancel goal");
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(void)goal_handle;
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return rclcpp_action::CancelResponse::ACCEPT;
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}
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void execute(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
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{
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RCLCPP_INFO(this->get_logger(), "Executing goal");
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rclcpp::Rate loop_rate(1);
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const auto goal = goal_handle->get_goal();
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auto feedback = std::make_shared<Fibonacci::Feedback>();
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auto & sequence = feedback->sequence;
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sequence.push_back(0);
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sequence.push_back(1);
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auto result = std::make_shared<Fibonacci::Result>();
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for (int i = 1; (i < goal->order) && rclcpp::ok(); ++i) {
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// Check if there is a cancel request
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if (goal_handle->is_canceling()) {
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result->sequence = sequence;
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goal_handle->canceled(result);
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RCLCPP_INFO(this->get_logger(), "Goal Canceled");
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return;
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}
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// Update sequence
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sequence.push_back(sequence[i] + sequence[i - 1]);
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// Publish feedback
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goal_handle->publish_feedback(feedback);
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RCLCPP_INFO(this->get_logger(), "Publish Feedback");
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loop_rate.sleep();
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}
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// Check if goal is done
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if (rclcpp::ok()) {
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result->sequence = sequence;
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goal_handle->succeed(result);
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RCLCPP_INFO(this->get_logger(), "Goal Succeeded");
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}
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}
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void handle_accepted(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
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{
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using namespace std::placeholders;
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// this needs to return quickly to avoid blocking the executor, so spin up a new thread
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std::thread{std::bind(&MinimalActionServer::execute, this, _1), goal_handle}.detach();
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}
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}; // class MinimalActionServer
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int main(int argc, char ** argv)
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{
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rclcpp::init(argc, argv);
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auto action_server = std::make_shared<MinimalActionServer>();
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rclcpp::spin(action_server);
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rclcpp::shutdown();
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return 0;
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}
客户端：
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#include <inttypes.h>
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#include <memory>
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#include <string>
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#include <iostream>
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#include "example_interfaces/action/fibonacci.hpp"
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#include "rclcpp/rclcpp.hpp"
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// TODO(jacobperron): Remove this once it is included as part of 'rclcpp.hpp'
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#include "rclcpp_action/rclcpp_action.hpp"
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class MinimalActionClient : public rclcpp::Node
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{
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public:
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using Fibonacci = example_interfaces::action::Fibonacci;
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using GoalHandleFibonacci = rclcpp_action::ClientGoalHandle<Fibonacci>;
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explicit MinimalActionClient(const rclcpp::NodeOptions & node_options = rclcpp::NodeOptions())
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: Node("minimal_action_client", node_options), goal_done_(false)
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{
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this->client_ptr_ = rclcpp_action::create_client<Fibonacci>(
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this->get_node_base_interface(),
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this->get_node_graph_interface(),
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this->get_node_logging_interface(),
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this->get_node_waitables_interface(),
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"fibonacci");
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this->timer_ = this->create_wall_timer(
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std::chrono::milliseconds(500),
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std::bind(&MinimalActionClient::send_goal, this));
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}
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bool is_goal_done() const
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{
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return this->goal_done_;
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}
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void send_goal()
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{
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using namespace std::placeholders;
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this->timer_->cancel();
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this->goal_done_ = false;
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if (!this->client_ptr_) {
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RCLCPP_ERROR(this->get_logger(), "Action client not initialized");
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}
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if (!this->client_ptr_->wait_for_action_server(std::chrono::seconds(10))) {
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RCLCPP_ERROR(this->get_logger(), "Action server not available after waiting");
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this->goal_done_ = true;
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return;
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}
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auto goal_msg = Fibonacci::Goal();
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goal_msg.order = 10;
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RCLCPP_INFO(this->get_logger(), "Sending goal");
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auto send_goal_options = rclcpp_action::Client<Fibonacci>::SendGoalOptions();
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send_goal_options.goal_response_callback =
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std::bind(&MinimalActionClient::goal_response_callback, this, _1);
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send_goal_options.feedback_callback =
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std::bind(&MinimalActionClient::feedback_callback, this, _1, _2);
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send_goal_options.result_callback =
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std::bind(&MinimalActionClient::result_callback, this, _1);
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auto goal_handle_future = this->client_ptr_->async_send_goal(goal_msg, send_goal_options);
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}
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private:
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rclcpp_action::Client<Fibonacci>::SharedPtr client_ptr_;
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rclcpp::TimerBase::SharedPtr timer_;
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bool goal_done_;
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void goal_response_callback(std::shared_future<GoalHandleFibonacci::SharedPtr> future)
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{
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auto goal_handle = future.get();
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if (!goal_handle) {
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RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");
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} else {
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RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");
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}
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}
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void feedback_callback(
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GoalHandleFibonacci::SharedPtr,
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const std::shared_ptr<const Fibonacci::Feedback> feedback)
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{
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RCLCPP_INFO(
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this->get_logger(),
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"Next number in sequence received: %" PRId32,
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feedback->sequence.back());
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}
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void result_callback(const GoalHandleFibonacci::WrappedResult & result)
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{
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this->goal_done_ = true;
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switch (result.code) {
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case rclcpp_action::ResultCode::SUCCEEDED:
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break;
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case rclcpp_action::ResultCode::ABORTED:
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RCLCPP_ERROR(this->get_logger(), "Goal was aborted");
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return;
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case rclcpp_action::ResultCode::CANCELED:
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RCLCPP_ERROR(this->get_logger(), "Goal was canceled");
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return;
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default:
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RCLCPP_ERROR(this->get_logger(), "Unknown result code");
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return;
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}
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RCLCPP_INFO(this->get_logger(), "Result received");
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for (auto number : result.result->sequence) {
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RCLCPP_INFO(this->get_logger(), "%" PRId32, number);
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}
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}
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}; // class MinimalActionClient
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int main(int argc, char ** argv)
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{
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rclcpp::init(argc, argv);
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auto action_client = std::make_shared<MinimalActionClient>();
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while (!action_client->is_goal_done()) {
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rclcpp::spin_some(action_client);
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}
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rclcpp::shutdown();
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return 0;
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}
那么这时候，就需要引入逻辑判断了，if
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RCLCPP_INFO(this->get_logger(), "Received goal request with order %d", goal->order);
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(void)uuid;
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// Let's reject sequences that are over 9000
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if (goal->order > 9000) {
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return rclcpp_action::GoalResponse::REJECT;
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}
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return rclcpp_action::GoalResponse::ACCEPT_AND_EXECUTE;
当需要计算量大于9000时，需要拒绝，这个数值可以修改。同样也可以发现这个程序运行时间比上一个案例中简单加减要长，并且过程也复杂。
那么中途如果不需要，就可以取消等。
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rclcpp_action::CancelResponse handle_cancel( const std::shared_ptr<GoalHandleFibonacci> goal_handle )
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{
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RCLCPP_INFO(this->get_logger(), "Received request to cancel goal");
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(void)goal_handle;
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return rclcpp_action::CancelResponse::ACCEPT;
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}
先看看效果^_^ 分别计算6，66……
计算6阶，还是一切正常的，但是66阶，明显就不对劲啦，这时候溢出，需要终止程序，无需继续下去：
上图中的有明显问题，-1323752223
虽然运行到最后，也会出现如下：
当然，可以查看更多详细信息，使用如下命令：
- ros2 action list
- ros2 action info /fibonacci
- ros2 action send_goal /fibonacci example_interfaces/action/Fibonacci order:\ 20\
示例程序中有大量的判断，下一节将融合图形化界面进行扩展。
文章来源: zhangrelay.blog.csdn.net，作者：zhangrelay，版权归原作者所有，如需转载，请联系作者。
原文链接：zhangrelay.blog.csdn.net/article/details/116668434
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