## 問題 我想創建一個類方法和實例方法 ## 方法 ### 類方法 ~~~ class Songs @_titles: 0 # Although it's directly accessible, the leading _ defines it by convention as private property. @get_count: -> @_titles constructor: (@artist, @title) -> Songs._titles++ Songs.get_count() # => 0 song = new Songs("Rick Astley", "Never Gonna Give You Up") Songs.get_count() # => 1 song.get_count() # => TypeError: Object <Songs> has no method 'get_count' ~~~ ### 實例方法 ~~~ class Songs _titles: 0 # Although it's directly accessible, the leading _ defines it by convention as private property. get_count: -> @_titles constructor: (@artist, @title) -> @_titles++ song = new Songs("Rick Astley", "Never Gonna Give You Up") song.get_count() # => 1 Songs.get_count() # => TypeError: Object function Songs(artist, title) ... has no method 'get_count' ~~~ ## 詳細 CoffeeScript把類方法放到類對象本身，而不是放到類對象的原型上，這樣能夠節省內存，且能夠集中式地存儲類屬性。