CODEWITHSUNDEEP
yaml-cpp
MrCartoonology
MrCartoonology

Reputation: 2067

error using yaml-cpp to get integer nested in key hierarchy

Initial Question

I have a config.yaml that has structure similar to

some_other_key: 34

a:
  b:
    c:
      d: 3

I thought I could do

YAML::Node config = YAML::LoadFile(config_filename.c_str());
int x  = config["a"]["b"]["c"]["d"].as<int>();

but I get 

terminate called after throwing an instance of
'YAML::TypedBadConversion<int>' 
what():  bad conversion

How do I descend through my config.yaml to extract a value like this? I also get that same exception if I mistype one of the keys in the path, so I can't tell from the error if I am accidentally working with a null node or if there is a problem converting a valid node's value to int

Follow up After First Replies

Thank you for replying! Maybe it is an issue with what is in the config.yaml? Here is a small example to reproduce,

yaml file: config2.yaml 

daq_writer:
  num: 3
  num_per_host: 3
  hosts:
    - local
  datasets:
    small:
      chunksize: 600

Python can read it:

Incidentally, I am on linux on rhel7, but from a python 3.6 environment, everything looks good:

$ python -c "import yaml; print(yaml.load(open('config2.yaml','r')))"
{'daq_writer': {'num_per_host': 3, 'num': 3, 'datasets': {'small': {'chunksize': 600}}, 'hosts': ['local']}}

C++ yaml-cpp code

The file yamlex.cpp:

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

int main() {
  YAML::Node config = YAML::LoadFile("config2.yaml");
  int small_chunksize = config["daq_writer"]["datasets"]["smal"]["chunksize"].as<int>();
}

When I compile and run this, I get:

(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ c++ --std=c++11 -Iinclude -Llib -lyaml-cpp yamlex.cpp
(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ LD_LIBRARY_PATH=lib ./a.out
terminate called after throwing an instance of 'YAML::TypedBadConversion<int>'
  what():  bad conversion
Aborted (core dumped)
(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ gcc --version
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4)

I have been able to read top level keys, like the some_other_key that I referenced above, but I got an error when I went after this nested key. Good to know that syntax works!

Upvotes: 1

Views: 2427

Answers (1)

Jesse Beder
Jesse Beder

Reputation: 34054

You have a typo in your keys: instead of "small", you wrote "smal".

Upvotes: 1

Related Questions