How to create the top object with yaml-cpp?

Question

I am trying to create a config file for my application using yaml-cpp, I am able to create map by

    YAML::Emitter emitter;
    emitter << YAML::BeginMap;
    emitter << YAML::Key << "Autoplay" << YAML::Value << "false";
    emitter << YAML::EndMap;

    std::ofstream ofout(file);
    ofout << emitter.c_str();

which outputs something like,

var1: value1
var2: value2

But how would I make the top object like,

Foo:
  var1: value1
  var2: value2

Bar:
  var3: value3
  var4: value4

and so on.. How do I get the Foo and the Bar like in the above code.

Guillaume Courrier · Accepted Answer · 2021-01-31 09:19:49Z

1

What you want to achieve is a map containing two keys Foo and Bar. Each of these containing a map as a value. The code below show you how you can achieve that:

// gcc -o example example.cpp -lyaml-cpp
#include <yaml-cpp/yaml.h>
#include <fstream>

int main() {
  std::string file{"example.yaml"};

  YAML::Emitter emitter;
  emitter << YAML::BeginMap;

  emitter << YAML::Key << "Foo" << YAML::Value;
  emitter << YAML::BeginMap; // this map is the value associated with the key "Foo"
  emitter << YAML::Key << "var1" << YAML::Value << "value1";
  emitter << YAML::Key << "var2" << YAML::Value << "value2";
  emitter << YAML::EndMap;

  emitter << YAML::Key << "Bar" << YAML::Value;
  emitter << YAML::BeginMap; // This map is the value associated with the key "Bar"
  emitter << YAML::Key << "var3" << YAML::Value << "value3";
  emitter << YAML::Key << "var4" << YAML::Value << "value4";
  emitter << YAML::EndMap;

  emitter << YAML::EndMap; // This ends the map containing the keys "Foo" and "Bar"

  std::ofstream ofout(file);
  ofout << emitter.c_str();
  return 0;
}

You have to see these sorts of structures with a recursive mindset. This code will create the example you gave.

answered Jan 31, 2021 at 9:19

Guillaume Courrier

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1 Comment

apoorv569 Over a year ago

Nice, I didn't know it was this simple :D. Thanks.

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