环境:ruby 1.9.2 + ubuntu 10.10 + rails 3.0.3
我们知道 ruby 中 扩展class ,写公用方法 ,或者 利用命名空间 来模块化 ,都是通过 module 来实现的 , 今天 看 rails 中 camelize 方法的源码的时候 , 发现 module 这样写的…..
active_support/inflector/methods.rb
module ActiveSupport # The Inflector transforms words from singular to plural, class names to table names, modularized class names to ones without, # and class names to foreign keys. The default inflections for pluralization, singularization, and uncountable words are kept # in inflections.rb. # # The Rails core team has stated patches for the inflections library will not be accepted # in order to avoid breaking legacy applications which may be relying on errant inflections. # If you discover an incorrect inflection and require it for your application, you'll need # to correct it yourself (explained below). module Inflector extend self # By default, +camelize+ converts strings to UpperCamelCase. If the argument to +camelize+ # is set to <tt>:lower</tt> then +camelize+ produces lowerCamelCase. # # +camelize+ will also convert '/' to '::' which is useful for converting paths to namespaces. # # Examples: # "active_record".camelize # => "ActiveRecord" # "active_record".camelize(:lower) # => "activeRecord" # "active_record/errors".camelize # => "ActiveRecord::Errors" # "active_record/errors".camelize(:lower) # => "activeRecord::Errors" # # As a rule of thumb you can think of +camelize+ as the inverse of +underscore+, # though there are cases where that does not hold: # # "SSLError".underscore.camelize # => "SslError" def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true) if first_letter_in_uppercase lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase } else lower_case_and_underscored_word.to_s[0].chr.downcase + camelize(lower_case_and_underscored_word)[1..-1] end end # Makes an underscored, lowercase form from the expression in the string. # # Changes '::' to '/' to convert namespaces to paths. # # Examples: # "ActiveRecord".underscore # => "active_record" # "ActiveRecord::Errors".underscore # => active_record/errors # # As a rule of thumb you can think of +underscore+ as the inverse of +camelize+, # though there are cases where that does not hold: # # "SSLError".underscore.camelize # => "SslError" def underscore(camel_cased_word) word = camel_cased_word.to_s.dup word.gsub!(/::/, '/') word.gsub!(/([A-Z]+)([A-Z][a-z])/,'\1_\2') word.gsub!(/([a-z\d])([A-Z])/,'\1_\2') word.tr!("-", "_") word.downcase! word end # Replaces underscores with dashes in the string. # # Example: # "puni_puni" # => "puni-puni" def dasherize(underscored_word) underscored_word.gsub(/_/, '-') end # Removes the module part from the expression in the string. # # Examples: # "ActiveRecord::CoreExtensions::String::Inflections".demodulize # => "Inflections" # "Inflections".demodulize # => "Inflections" def demodulize(class_name_in_module) class_name_in_module.to_s.gsub(/^.*::/, '') end # Creates a foreign key name from a class name. # +separate_class_name_and_id_with_underscore+ sets whether # the method should put '_' between the name and 'id'. # # Examples: # "Message".foreign_key # => "message_id" # "Message".foreign_key(false) # => "messageid" # "Admin::Post".foreign_key # => "post_id" def foreign_key(class_name, separate_class_name_and_id_with_underscore = true) underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id") end # Ruby 1.9 introduces an inherit argument for Module#const_get and # #const_defined? and changes their default behavior. if Module.method(:const_get).arity == 1 # Tries to find a constant with the name specified in the argument string: # # "Module".constantize # => Module # "Test::Unit".constantize # => Test::Unit # # The name is assumed to be the one of a top-level constant, no matter whether # it starts with "::" or not. No lexical context is taken into account: # # C = 'outside' # module M # C = 'inside' # C # => 'inside' # "C".constantize # => 'outside', same as ::C # end # # NameError is raised when the name is not in CamelCase or the constant is # unknown. def constantize(camel_cased_word) names = camel_cased_word.split('::') names.shift if names.empty? || names.first.empty? constant = Object names.each do |name| constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name) end constant end else def constantize(camel_cased_word) #:nodoc: names = camel_cased_word.split('::') names.shift if names.empty? || names.first.empty? constant = Object names.each do |name| constant = constant.const_defined?(name, false) ? constant.const_get(name) : constant.const_missing(name) end constant end end # Turns a number into an ordinal string used to denote the position in an # ordered sequence such as 1st, 2nd, 3rd, 4th. # # Examples: # ordinalize(1) # => "1st" # ordinalize(2) # => "2nd" # ordinalize(1002) # => "1002nd" # ordinalize(1003) # => "1003rd" def ordinalize(number) if (11..13).include?(number.to_i % 100) "#{number}th" else case number.to_i % 10 when 1; "#{number}st" when 2; "#{number}nd" when 3; "#{number}rd" else "#{number}th" end end end end end
发现 了这样的写法
module A module B extend self ..... end end
extend self 有何作用?
先来看个demo:
module Foo module Bar extend self # self => Foo::Bar def hello p "hello" end end end class Klass include Foo::Bar end Klass.new.hello # "hello" Foo::Bar.hello # "hello" Klass.hello # undefined method `hello' for Klass:Class (NoMethodError)
发现 module 中的方法 可以当作模块方法 直接被Module调用 , 被include 到class 中后 , 依然还是 class 的实例方法 , 恩,不错,以后 像下面 这样的写法, 都要 改改了:
module A def self.foo end end
改成这样:
module A extend self def foo end end
demo里的extend self 其实就是 Foo::Bar.extend(Foo::Bar)
所以 可以 更动态的 写成这样:
module Foo module Bar def hello p "hello" end end end class Klass include Foo::Bar end Foo::Bar.extend(Foo::Bar) Klass.new.hello # "hello" Foo::Bar.hello # "hello" Klass.hello # undefined method `hello' for Klass:Class (NoMethodError)
环境:ruby 1.9.2 + rails 3.0.3 + ubuntu 10.10
scaffold 生成的 form_for 对应的 boolean 类型 是check_box , 数据库中 值是 1 check_box就选中, 是 0 就不选中, 但是不是 form_for 的话 ,check_box_tag 怎么实现呢
仿照 form_for check_box 生成的代码:
<input name="user[abc]" type="hidden" value="0" /> <input checked="checked" id="user_abc" name="user[abc]" type="checkbox" value="1" />
可以看出 多生成了 一段 hidden , 为什么 ?
因为 check_box 的工作原理是 :
选中了 就传check_box 的参数 , 不选中 不传 check_box 的 参数
所以上面 选中的话,传的值是 1
没选中的话, 传的是 0
所以check_box_tag 的话,就应该这样写了.
<%= hidden_field_tag "user[abc]" , 0 %> <%= check_box_tag "user[abc]" , 1 , (true if ele.abc == 1) %>
注意 需要 添加 hidden 域 , 并且 需要在 checkbox 的上面