CoffeeScript 修饰模式
2018-06-08 14:00 更新
修饰模式
问题
你有一组数据,需要在多个过程、可能变换的方式下处理。
解决方案
使用修饰模式来构造如何更改应用。
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
class TextProcessor
constructor: (@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>
讨论
TextProcessor服务有修饰的作用,可将个人、专业文本处理器绑定在一起。这使miniMarkdown和stripComments组件只专注于处理一行文本。未来的开发人员只需要编写函数返回一个字符串,并将它添加到阵列的处理器即可。
我们甚至可以修改现有的修饰对象动态:
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>"
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