第 0 行第 0 列错误：加载 YAML 文件时转换错误

Question

下面是我已经通过 YAMLint 验证过的 yaml 示例文件 URL 但在使用 yaml-cpp 库函数 LoadFile 加载此文件时，出现错误：

"Error at line 0, column 0: bad conversion while loading YAML file"

示例 yaml 文件：

%YAML 1.1
---
name: abcd_server_interface
spec_type: interface
spec_version: 1
description: 'Interface for capability ABCD Slam'
default_provider: abcd_server/abcd_server_provider
interface: {}
topics: {
     provides: {

       provide: {
       name: '/3d_pose_graph',
       type: '-',
       description: '-',
       },

       provide: {
       name: '/key_frame_msgs',
       type: '-',
       description: '-'
         }, 

       provide: {
       name: '/pc_map',
       type: 'sensor_msgs/PointCloud2',
       description: 'Point cloud'
         },

       provide: {
       name: '/3dOctomap',
       type: '-',
       description: '-'
         },

       provide: {
       name: '/poseOfRobots',
       type: '-',
       description: '-'
         },

       provide: {
       name: '/occupied_calls_vis_array',
       type: '-',
       description: '-'
         },
     },    
     requires: {

      require: {
       name: '/image_depth_throttled',
       type: 'sensor_msgs/Image',
       description: 'Sensor Image',
       },

       require: {
       name: '/image_color_throttled/compressed',
       type: 'sensor_msgs/CompressedImage',
       description: 'Sensor compressed image',
       },

      require: {
       name: '/statistics',
       type: '-',
       description: '-',
       },

       require: {
       name: '/initialpose',
       type: '-',
       description: '-',
       },

       require: {
       name: '/reset_rgbdserver',
       type: 'std_msgs/Bool',
       description: 'To reset server',
       },

       require: {
       name: '/scan',
       type: 'sensor_msgs/LaserScan',
       description: 'laser scan data',
       },

       require: {
       name: '/tf',
       type: 'tf2_msgs/TFMessage',
       description: 'tf',
       },

       require: {
       name: '/tf_static',
       type: 'tf2_msgs/TFMessage',
       description: 'tf static',
       },      

      }
   }

Parameter: {
       parameter: {
       name: 'max_delay',
       value: '100'
       },

       parameter: {
       name: 'rgb_hints',
       value: 'compressed'
       },

       parameter: {
       name: 'depth_hints',
       value: 'raw'
       },

       parameter: {
       name: 'bot_frame',
       value: '/base_link'
       },

       parameter: {
       name: 'kinect_frame',
       value: '/camera_depth_optical_frame'
       },

       parameter: {
       name: 'minZ',
       value: '-1.0'
       },

       parameter: {
       name: 'maxZ',
       value: '4.0'
       },    
}

这是我编写的用于替换 yaml 文件中参数部分的参数名称 (max_delay) 值的代码。

#include <fstream>
#include <iostream>
#include "yaml-cpp/yaml.h" 

using namespace std;

bool UpdateYAMLFile(const string& sYamlFile, const string& sParamName2Update, const string sValue)
{
    bool bRet = false;
    try
    {        
        //YAML::Node head_ = YAML::LoadFile(sYamlFile);
                YAML::Node head_ = YAML::LoadFile(sYamlFile);

                //YAML::Node head_ = YAML::Load(sYamlFile);
std::cout << head_.size();

                cout<<"ramesh"<<endl;
        for (YAML::iterator ith = head_.begin();ith != head_.end(); ++ith)
        {
            YAML::Node sub1_ = ith->second;
            for (YAML::iterator itc = sub1_.begin();itc != sub1_.end(); ++itc)
            {
                string sParam = itc->second["name"].as<std::string>(); //cout << sParam  << endl;
                if(sParam == sParamName2Update)
                {
                    itc->second["value"] = sValue;
                    bRet = true;
                }
            }
        }       
        ofstream fout(sYamlFile); 
        fout << head_;          //cout << head_ << "\n";
    }
    catch (const YAML::Exception& e)
    {
        cout << "ERROR: Updation of yaml file " << sYamlFile << "Failed: Exception: " << e.what() << "\n";
    }
    return bRet;
}
//driver
int main(int argc, char** argv) 
{

    int bRet = UpdateYAMLFile("sample.yaml", "max_delay","1150");

    if(bRet == true)
        cout << "SUCCESS: YAML file updated..\n";
    else
        cout << "ERROR: YAML file update FAILED...\n";

  return 0;
}

基本上UpdateYAMLFile API 将更新示例yaml 文件中的max_dealy 参数值。使用这个 API 我应该能够更新参数部分中的所有参数（max_delay、rgb_hints、depth_hints、minZ、maxZ）示例 yaml 文件。

命令:

 g++ -std=c++0x yaml.cpp -o res /usr/lib/x86_64-linux-gnu/libyaml-cpp.a

Answer 1

您的地图访问似乎差了一个。您的地图嵌套了三层：

topics: {                      // first key/value pair
     provides: {               // second key/value pair
       provide: {              // third key/value pair
       name: '/3d_pose_graph', // now lookup the name attribute
       type: '-',
       description: '-',
       }
     }
}

您的第三张地图也有问题：所有的键都是 "provide"。这不是真正的地图，它将被解析为单个 key/value 对（每个都覆盖前一个）。您可以将其制成如下列表：

topics: {
   provides: [               // this is now a list
     {
       name: '/3d_pose_graph',
       type: '-',
       description: '-',
     }, {
       name: '/key_frame_msgs',
       type: '-',
       description: '-'
     }, ...
   ]
}

此外，您不必在不知道其中内容的情况下盲目地遍历地图的值。为什么不直接访问密钥：

for (YAML::Node provides : head_["topics"]["provides"]) {
  if (provides["name"].as<std::string>() == sParamName2Update) {
    provides["name"] = sValue;
  }
}

第 0 行第 0 列错误：加载 YAML 文件时转换错误

Error at line 0, column 0: bad conversion while loading YAML file

c++

file

yaml-cpp

c++11

示例 yaml 文件：