为什么
Ruby的内置JSON不能反序列化简单的JSON原语,我该如何解决它？
irb(main):001:0> require 'json'
#=> true
irb(main):002:0> objects = [ {},[],42,"",true,nil ]
#=> [{},true]
irb(main):012:0> objects.each do |o|
irb(main):013:1* json = o.to_json
irb(main):014:1> begin
irb(main):015:2* p JSON.parse(json)
irb(main):016:2> rescue Exception => e
irb(main):017:2> puts "Error parsing #{json.inspect}: #{e}"
irb(main):018:2> end
irb(main):019:1> end
{}
[]
Error parsing "42": 706: unexpected token at '42'
Error parsing "\"\"": 706: unexpected token at '""'
Error parsing "true": 706: unexpected token at 'true'
Error parsing "null": 706: unexpected token at 'null'
#=> [{},nil]
irb(main):020:0> RUBY_DESCRIPTION
#=> "ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.7.0]"
irb(main):022:0> JSON::VERSION
#=> "1.4.2"
解决方法
RFC 4627: The application/json Media Type for JavaScript Object Notation (JSON)有这个说：
2. JSON Grammar
A JSON text is a sequence of tokens. The set of tokens includes six
structural characters,strings,numbers,and three literal names.
A JSON text is a serialized object or array.
JSON-text = object / array
[...]
2.1. Values
A JSON value MUST be an object,array,number,or string,or one of
the following three literal names:
false null true
如果你在六个样本对象上调用to_json,我们得到：
>> objects = [ {},nil ]
>> objects.map { |o| puts o.to_json }
{}
[]
42
""
true
null
所以第一个和第二个是有效的JSON文本,而后四个不是有效的JSON文本,即使它们是有效的JSON值.
JSON.parse想要它所谓的JSON文档：
Parse the JSON document source into a Ruby data structure and return it.
也许JSON文档是RFC 4627称为JSON文本的库的术语.如果是这样,那么引发异常是对无效输入的合理响应.
如果你强行包装和解开所有东西：
objects.each do |o|
json = o.to_json
begin
json_text = '[' + json + ']'
p JSON.parse(json_text)[0]
rescue Exception => e
puts "Error parsing #{json.inspect}: #{e}"
end
end
正如您在评论中所指出的,在调用者想要使用：symbolize_names选项的情况下,使用数组作为包装器比对象更好.像这样包装意味着你将永远为JSON.parse提供一个JSON文本,一切都应该没问题.