Ruby：解析純文本的結構化塊

Question

我正在爲CSS文件編寫一個簡單的ruby解析器，而且我非常難以獲得一塊CSS（即選擇器以及緊跟在花括號之後的所有內容它）作爲一個紅寶石物體，我可以執行我的黑暗和討厭的魔法。

理想情況下，我想獲得每個屬性/值和選擇器的紅寶石散列。有沒有什麼清楚和容易理解的方式如何做到這一點？

Answer 1

正如在評論中提到的那樣，自己做一個有趣的練習是很愚蠢的。我會將css文件讀入一個字符串，然後用正則表達式對其進行掃描。

Ruby - Convert File to String

http://www.ruby-doc.org/core-1.9.3/String.html#method-i-scan

用於測試正則表達式：http://rubular.com/

Answer 2

每個人都應該寫一個解析器。

這應該讓你開始...

require 'parslet' 
require 'ostruct' 
require 'pp' 

class Parser < Parslet::Parser 
    rule(:opencurl) { str('{') } 
    rule(:closecurl) { str('}') } 
    rule(:space)  { str(' ') } 
    rule(:space?)  { space.maybe } 
    rule(:comma)  { str(',') } 
    rule(:semi)  { str(';') } 
    rule(:colon)  { str(':') } 
    rule(:eol)  { str("\r").maybe >> str("\n") } 
    rule(:eol?)  { eol.maybe } 
    rule(:indent?) { str(" ").repeat(0) } 
    rule(:ws?)  {indent? >> eol? >> indent?} 

    rule(:value)  { (semi.absent? >> any).repeat(1).as(:value) } #cheating 

    rule(:word)  { match['a-zA-Z0-9'].repeat(1) } 
    rule(:property) { (word >> (str("-") >> word).repeat(0)).as(:property) } 
    rule(:setting) { (indent? >> property >> colon >> indent? >> value >> semi >> eol?) } 
    rule(:body?)  { setting.repeat(0).as(:body) } 
    rule(:block)  { opencurl >> ws? >> body? >> ws? >> closecurl >> ws? } 
    rule(:selector_expression) { (opencurl.absent? >> any).repeat(1) } #cheating 
    rule(:scope)  { ws? >> selector_expression.as("selector") >> indent? >> block.as(:settings) } 

    rule(:css?)  { (eol.repeat(0) >> scope).repeat(0) } 
    root(:css?) 
end 

class MyTransform < Parslet::Transform 
    rule(:property => simple(:p), :value => simple(:v)) { OpenStruct.new(p:p,v:v) } 
    rule(:body => sequence(:b)) { b.each_with_object({}){|i,o| o[i.p] = i.v} } 
end 

css = <<-css 
    h2{ background-image: url(abc);} 
    #bob { 
    background-image: url(abc); 
    background-color: red; 
} 
css 

par = Parser.new.parse(css) 
tar = MyTransform.new.apply(par) 
pp tar 

輸出：

[{"selector"=>"h2", :settings=>{"background-image"=>"url(abc)"}}, 
{"selector"=>"#bob ", 
    :settings=> 
    {"background-image"=>"url(abc)", "background-color"=>"red"}}]