装饰者模式

## 问题 你有一组数据，你需要对它们进行多次不同可处理。 ## 方法 使用装饰者模式来构建你的处理方式。 ~~~ miniMarkdown = (line) -> if match = line.match /^(#+)\s*(.*)$/ headerLevel = match[1].length headerText = match[2] "<h#{headerLevel}>#{headerText}</h#{headerLevel}>" else if line.length > 0 "<p>#{line}</p>" else '' stripComments = (line) -> line.replace /\s*\/\/.*$/, '' # Removes one-line, double-slash C-style comments TextProcessor = (@processors) -> reducer: (existing, processor) -> if processor processor(existing or '') else existing processLine: (text) -> @processors.reduce @reducer, text processString: (text) -> (@processLine(line) for line in text.split("\n")).join("\n") exampleText = ''' # A level 1 header A regular line // a comment ## A level 2 header A line // with a comment ''' processor = new TextProcessor [stripComments, miniMarkdown] processor.processString exampleText # => "<h1>A level 1 header</h1>\n<p>A regular line</p>\n\n<h2>A level 2 header</h2>\n<p>A line</p>" ~~~ ### 结果 ~~~ <h1>A level 1 header</h1> <p>A regular line</p> <h2>A level 1 header</h2> <p>A line</p> ~~~ ## 详解 TextProcessor正在这里就是一个装饰者的角色，把独立的不同的文本处理方式放到了一起。miniMarkdown和stripComments这两个组件被解放出来，专注于处理单行文本。其他开发者只需要编写这样的函数，返回一个字符串，并且把这个函数添加到处理器组中。 我们甚至可以随时修改现有的装饰者： ~~~ smilies = ':)' : "smile" ':D' : "huge_grin" ':(' : "frown" ';)' : "wink" smilieExpander = (line) -> if line (line = line.replace symbol, "<img src='#{text}.png' alt='#{text}' />") for symbol, text of smilies line processor.processors.unshift smilieExpander processor.processString "# A header that makes you :) // you may even laugh" # => "<h1>A header that makes you <img src='smile.png' alt='smile' /></h1>" processor.processors.shift() # => "<h1>A header that makes you :)</h1>" ~~~