{
    "mode": "ri",
    "parameter": "Psych::Nodes",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/ri/Psych%3A%3ANodes/json",
    "generated": "2026-06-16T03:48:29Z",
    "sections": {
        "Psych::Nodes": {
            "content": "(from gem psych-5.4.0)\n------------------------------------------------------------------------",
            "subsections": []
        },
        "Overview": {
            "content": "When using Psych.load to deserialize a YAML document, the document is\ntranslated to an intermediary AST.  That intermediary AST is then\ntranslated in to a Ruby object graph.\n\nIn the opposite direction, when using Psych.dump, the Ruby object graph\nis translated to an intermediary AST which is then converted to a YAML\ndocument.\n\nPsych::Nodes contains all of the classes that make up the nodes of a\nYAML AST.  You can manually build an AST and use one of the visitors\n(see Psych::Visitors) to convert that AST to either a YAML document or\nto a Ruby object graph.\n\nHere is an example of building an AST that represents a list with one\nscalar:\n\n# Create our nodes\nstream = Psych::Nodes::Stream.new\ndoc    = Psych::Nodes::Document.new\nseq    = Psych::Nodes::Sequence.new\nscalar = Psych::Nodes::Scalar.new('foo')\n\n# Build up our tree\nstream.children << doc\ndoc.children    << seq\nseq.children    << scalar\n\nThe stream is the root of the tree.  We can then convert the tree to\nYAML:\n\nstream.toyaml => \"---\\n- foo\\n\"\n\nOr convert it to Ruby:\n\nstream.toruby => [[\"foo\"]]\n",
            "subsections": [
                {
                    "name": "YAML AST Requirements",
                    "content": "A valid YAML AST must have one Psych::Nodes::Stream at the root.\nA Psych::Nodes::Stream node must have 1 or more Psych::Nodes::Document\nnodes as children.\n\nPsych::Nodes::Document nodes must have one and only one child.\nThat child may be one of:\n\n* Psych::Nodes::Sequence\n* Psych::Nodes::Mapping\n* Psych::Nodes::Scalar\n\nPsych::Nodes::Sequence and Psych::Nodes::Mapping nodes may have many\nchildren, but Psych::Nodes::Mapping nodes should have an even number of\nchildren.\n\nAll of these are valid children for Psych::Nodes::Sequence and\nPsych::Nodes::Mapping nodes:\n\n* Psych::Nodes::Sequence\n* Psych::Nodes::Mapping\n* Psych::Nodes::Scalar\n* Psych::Nodes::Alias\n\nPsych::Nodes::Scalar and Psych::Nodes::Alias are both terminal nodes and\nshould not have any children.\n\n\n\n\n\n\n\n------------------------------------------------------------------------"
                }
            ]
        }
    },
    "flags": [],
    "examples": [],
    "see_also": []
}