Reputation: 3732

Ruby parse through string

I have a string that looks like below, and I have to remove everything between the first bracket and the last bracket. All bets are off, on what's in between (regarding other brackets). What would be the best aproach, thanks.

'[

        { "foo":
            {"bar":"foo",
                "bar": {
                    ["foo":"bar", "foo":"bar"]
                }
            }
        }

    ],

"foo":"bar","foo":"bar"'

result:

  ',

    "foo":"bar","foo":"bar"'

Upvotes: 3

Answers (5)

Nigel Thorne

Reputation: 21548

You could use something like Parslet to write a parser. Here's an example I wrote, based on the JSON grammer from http://www.json.org/

require 'parslet'

#This needs a few more 'as' calls to annotate the output 
class JSONParser < Parslet::Parser
  rule(:space)              { match('[\s\n]').repeat(1)}
  rule(:space?)             { space.maybe }
  rule(:digit)              { match('[0-9]') }
  rule(:hexdigit)           { match('[0-9a-fA-F]') }

  rule(:number)             { space? >> str('-').maybe >> 
                                (str('0') | (match('[1-9]') >> digit.repeat)) >> 
                                (str('.') >> digit.repeat).maybe >> 
                                ((str('e')| str('E')) >> (str('+')|str('-')).maybe >> digit.repeat ).maybe }

  rule(:escaped_character)  { str('\\') >> (match('["\\\\/bfnrt]') | (str('u') >> hexdigit.repeat(4,4))) }
  rule(:string)             { space? >> str('"') >> (match('[^\"\\\\]') | escaped_character).repeat >> str('"') }
  rule(:value)              { space? >> (string | number | object | array | str('true') | str('false') | str('null')) }

  rule(:pair)               { string >> str(":") >> value }
  rule(:pair_list)          { pair >> (space? >> str(',') >> pair).repeat }
  rule(:object)             { str('{') >> space? >> pair_list.maybe >> space? >> str('}') }

  rule(:value_list)         { value >> (space? >> str(',') >> value).repeat }
  rule(:array)              { space? >> str('[') >> space? >> value_list.maybe >> space? >> str(']') >> space?}

  rule(:json)               { value.as('value') >> (space? >> str(',') >> value.as('value')).repeat }
  root(:json)
end

# I've changed your doc to be a list of JSON values
doc = '[

        { "foo":
            {"bar":"foo",
                "bar": [
                    {"foo":"bar", "foo":"bar"}
                ]
            }
        }

    ],

{"foo":"bar"},{"foo":"bar"}'

puts JSONParser.new.parse(doc)[1..-1].map{|value| value["value"]}.join(",")
# => {"foo":"bar"},{"foo":"bar"}

However as your document isn't valid JSON (as far as I know).. then you can change the above...

require 'parslet'

class YourFileParser < Parslet::Parser
  rule(:space)              { match('[\s\n]').repeat(1)}
  rule(:space?)             { space.maybe }
  rule(:digit)              { match('[0-9]') }
  rule(:hexdigit)           { match('[0-9a-fA-F]') }

  rule(:number)             { space? >> str('-').maybe >> 
                                (str('0') | (match('[1-9]') >> digit.repeat)) >> 
                                (str('.') >> digit.repeat).maybe >> 
                                ((str('e')| str('E')) >> (str('+')|str('-')).maybe >> digit.repeat ).maybe }

  rule(:escaped_character)  { str('\\') >> (match('["\\\\/bfnrt]') | (str('u') >> hexdigit.repeat(4,4))) }
  rule(:string)             { space? >> str('"') >> (match('[^\"\\\\]') | escaped_character).repeat >> str('"') }
  rule(:value)              { space? >> (string | number | object | array | str('true') | str('false') | str('null')) }

  rule(:pair)               { string >> str(":") >> value }
  rule(:pair_list)          { (pair|value) >> (space? >> str(',') >> (pair|value)).repeat }
  rule(:object)             { str('{') >> space? >> pair_list.maybe >> space? >> str('}') }

  rule(:value_list)         { (pair|value) >> (space? >> str(',') >> (pair|value)).repeat }
  rule(:array)              { space? >> str('[') >> space? >> value_list.maybe >> space? >> str(']') >> space?}

  rule(:yourdoc)           { (pair|value).as('value') >> (space? >> str(',') >> (pair|value).as('value')).repeat }
  root(:yourdoc)
end

doc = '[

        { "foo":
            {"bar":"foo",
                "bar": {
                    ["foo":"bar", "foo":"bar"]
                }
            }
        }

    ],

"foo":"bar","foo":"bar"'

puts YourFileParser.new.parse(doc)[1..-1].map{|value| value["value"]}.join(",")

Upvotes: 0

Tilo

Reputation: 33732

you need multi-line mode:

str.gsub(/\[.*\]/m, '')

Upvotes: 0

Andy Waite

Reputation: 11076

It's difficult to tell what you're trying to achieve, but that looks like JSON to me so it would probably be much easier to parse it and then manipulate it that way.

Upvotes: 0