| // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| /** |
| * Takes a parsed and composed YAML document (what the spec calls the |
| * "representation graph") and creates native Dart objects that represent that |
| * document. |
| */ |
| class _Constructor extends _Visitor { |
| /** The root node of the representation graph. */ |
| _Node root; |
| |
| /** Map from anchor names to the most recent Dart node with that anchor. */ |
| Map<String, Dynamic> anchors; |
| |
| _Constructor(this.root) : this.anchors = {}; |
| |
| /** Runs the Constructor to produce a Dart object. */ |
| construct() => root.visit(this); |
| |
| /** Returns the value of a scalar. */ |
| visitScalar(_ScalarNode scalar) => scalar.value; |
| |
| /** Converts a sequence into a List of Dart objects. */ |
| visitSequence(_SequenceNode seq) { |
| var anchor = getAnchor(seq); |
| if (anchor != null) return anchor; |
| var dartSeq = setAnchor(seq, []); |
| dartSeq.addAll(super.visitSequence(seq)); |
| return dartSeq; |
| } |
| |
| /** Converts a mapping into a Map of Dart objects. */ |
| visitMapping(_MappingNode map) { |
| var anchor = getAnchor(map); |
| if (anchor != null) return anchor; |
| var dartMap = setAnchor(map, new YamlMap()); |
| super.visitMapping(map).forEach((k, v) { dartMap[k] = v; }); |
| return dartMap; |
| } |
| |
| /** |
| * Returns the Dart object that already represents [anchored], if such a thing |
| * exists. |
| */ |
| getAnchor(_Node anchored) { |
| if (anchored.anchor == null) return null; |
| if (anchors.containsKey(anchored.anchor)) return anchors[anchored.anchor]; |
| } |
| |
| /** Records that [value] is the Dart object representing [anchored]. */ |
| setAnchor(_Node anchored, value) { |
| if (anchored.anchor == null) return value; |
| anchors[anchored.anchor] = value; |
| return value; |
| } |
| } |