c++ - Boost ptree 顶级数组

Question

我想让 write_json 输出一个顶级数组，效果如下:

[{...},{...},{...},...,{...}]

但是当我将列表传递给 write_json 时，它会转换为充满空白键的 json。

{"":{...},"":{...},"":{...},..."":{...}}

使用 add_child 实际上尊重数组并给了我最接近的东西:

{"Some Key":[{...},{...},{...},...,{...}]}

但这仍然不是我想要的。

知道如何使该数组成为顶级吗？

Answer 1

Boost 没有 JSON 库(也没有 XML 库)。它有一个 Property Tree 库(恰好包含一个 JSON 兼容的表示)。

您遇到的限制非常清楚地记录在案:http://www.boost.org/doc/libs/1_62_0/doc/html/property_tree/parsers.html#property_tree.parsers.json_parser

The property tree dataset is not typed, and does not support arrays as such. Thus, the following JSON / property tree mapping is used:

• JSON objects are mapped to nodes. Each property is a child node.
• JSON arrays are mapped to nodes. Each element is a child node with an empty name. If a node has both named and unnamed child nodes, it cannot be mapped to a JSON representation.
• JSON values are mapped to nodes containing the value. However, all type information is lost; numbers, as well as the literals "null", "true" and "false" are simply mapped to their string form.
• Property tree nodes containing both child nodes and data cannot be mapped.
• JSON round-trips, except for the type information loss.

它继续显示您遇到的确切示例。