Yaml-cpp(新API)-嵌套图/序列组合和迭代

问题描述

此api对地图和序列的处理存在一些非常基本的问题.说我有以下结构:

I'm having quite fundamental problems with this api's handling of maps vs sequences. Say I have the following structure:

foo_map["f1"] = "one";
foo_map["f2"] = "two";
bar_map["b1"] = "one";
bar_map["b2"] = "two";

我希望将其转换为以下YAML文件:

I want this to be converted to the following YAML file:

Node:
    - Foo:
      f1 : one
      f2 : two
    - Bar:
      b1 : one
      b2 : two

我可以这样做:

node.push_back("Foo");
node["Foo"]["b1"] = "one";
...
node.push_back("Bar");

但是，最后一行的节点现在已从序列转换为映射，但出现异常.我唯一的方法是输出地图:

However at the last line node has now been converted from a sequence to a map and I get an exception. The only way I can do this is by outputting a map of maps:

Node:
    Foo:
      f1 : one
      f2 : two
    Bar:
      b1 : one
      b2 : two

这是我无法读回此类文件的问题.如果我遍历Node，那么即使没有异常，我也无法获得节点迭代器的类型.

The problem with this is if I cannot read back such files. If I iterate over Node, I'm unable to even get the type of the node iterator without getting an exception.

YAML::Node::const_iterator n_it = node.begin();

for (; n_it != config.end(); n_it++) {
        if (n_it->Type() == YAML::NodeType::Scalar) {
            // throws exception
        }
    }

这应该很简单，但是一直让我发疯！

This should be very simple to handle but has been driving me crazy!

推荐答案

YAML文件

Node:
    - Foo:
      f1 : one
      f2 : two
    - Bar:
      b1 : one
      b2 : two

可能不是您所期望的.它是一个映射，具有单个键/值对；键是Node，值是一个序列；并且该序列的每个条目都是具有三个键/值对的映射，并且与Foo相关的值为null.最后一部分可能不是您期望的.我猜您想要的更像是您实际得到的东西，即:

is probably not what you expect. It is a map, with a single key/value pair; the key is Node and the value is a sequence; and each entry of that sequence is a map with three key/value pairs, and the value associated with, e.g., the Foo, is null. This last part is probably not what you expected. I'm guessing you wanted something more like what you actually got, i.e.:

Node:
    Foo:
      f1 : one
      f2 : two
    Bar:
      b1 : one
      b2 : two

现在的问题是如何解析此结构.

The question now is how to parse this structure.

YAML::Node root = /* ... */;
YAML::Node node = root["Node"];

// We now have a map node, so let's iterate through:
for (auto it = node.begin(); it != node.end(); ++it) {
  YAML::Node key = it->first;
  YAML::Node value = it->second;
  if (key.Type() == YAML::NodeType::Scalar) {
    // This should be true; do something here with the scalar key.
  }
  if (value.Type() == YAML::NodeType::Map) {
    // This should be true; do something here with the map.
  }
}

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