Parsing json/yaml array with yaml-cpp

Question

I am using yaml-cpp for my configuration files parsing because I have to be able to parse yaml and json files and this is the only cpp library supporting yaml 1.2 I have found. While parsing, I do not ask for key because I do not know what component is current configuration file for. Also I am using ncurses for displaying the configuration file content.

While parsing configuration files which include arrays I am not getting these arrays. Program just skips them.

Example of yaml configuration file:

SLICE_POSITION: 285
SLICE_HEIGHT: 15
OUTPUT_ADDRESS: "localhost:3335"
VIRTCAM_IDS:
            - 0
            - 1
            - 2

Example of json configuration file:

{
"width" : 1366,
"mappings" : {
  "x" : [ "mt_position_x" ],
  "y" : [ "mt_position_y" ]
},
"active_quadrangle" : {
  "bottom_left" : "[1472;4698;0]",
  "bottom_right" : "[5654;4698;0]",
  "top_left" : "[1472;1408;0]",
  "top_right" : "[5654;1408;0]"
},
"x" : 0.0,
"y" : 0.0
}

My code:

YAML::Node config = YAML::LoadFile(fileName);
for(YAML::const_iterator it = config.begin(); it != config.end();) {
    const char* key = (it->first.as<std::string>()).c_str();
    mvprintw(i, 4, key);
    i++; // row number
    ++it;
}

Keys I am getting from yaml file:

VIRTCAM_IDS                                   
SLICE_POSITION                                
SLICE_HEIGHT                                  
OUTPUT_ADDRESS

Keys I am getting from json file:

uuid                                          
mappings                                      
width                                         
device                                        
sensor_type                                   
target                                        
height                                        
x                                             
active_quadrangle                             
y

So can somebody tell me, how to parse this, so I can get to the arrays(and their values)? Also is there any way I can get items in right order?

Thanks for any answer!

Jesse Beder · Accepted Answer · 2015-03-13 05:10:08Z

1

When you're looping through the map, you're just reading the keys with it->first. To read the values too, you need it->second:

YAML::Node config = YAML::LoadFile(fileName);
for (YAML::const_iterator it = config.begin(); it != config.end(); ++it) {
  std::string key = it->first.as<std::string>();
  YAML::Node value = it->second;
  // here, you can check what type the value is (e.g., scalar, sequence, etc.)
  switch (value.Type()) {
    case YAML::NodeType::Scalar: // do stuff
    case YAML::NodeType::Sequence: // do stuff
    // etc.
  }
}

answered Mar 13, 2015 at 5:10

Jesse Beder

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1 Comment

Desana Daxnerová Over a year ago

Oh thank you, I tried this, but I called .Type() on iterator, so it threw exception on me. It haven't occurred to me to try it on iterator value.

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