我刚刚开始使用我的第一个Ruby on Rails web应用程序。我有很多不同的模型,视图,控制器等等。
我想找到一个好地方粘真正的全局常数的定义,适用于我的整个应用程序。特别是,它们适用于我的模型的逻辑,并在我的视图中所做的决定。我找不到任何DRY的地方来放置这些定义,它们既适用于我的所有模型,也适用于我的所有视图。
举个具体的例子,我想要一个常量colors = ['white', 'blue', 'black', 'red', 'green']。这在模型和视图中都被广泛使用。我可以在哪里只在一个地方定义它,以便它是可访问的?
我的尝试:
Constant class variables in the model.rb file that they're most associated with, such as @@COLOURS = [...]. But I couldn't find a sane way to define it so that I can write in my views Card.COLOURS rather than something kludgy like Card.first.COLOURS.
A method on the model, something like def colours ['white',...] end - same problem.
A method in application_helper.rb - this is what I'm doing so far, but the helpers are only accessible in views, not in models
I think I might have tried something in application.rb or environment.rb, but those don't really seem right (and they don't seem to work either)
是否没有办法定义从模型和视图都可以访问的东西?我的意思是,我知道模型和视图应该是分开的,但在某些领域,它们肯定会有需要引用相同的领域特定知识的时候?
一些选项:
使用常量:
class Card
COLOURS = ['white', 'blue', 'black', 'red', 'green', 'yellow'].freeze
end
惰性加载使用类实例变量:
class Card
def self.colours
@colours ||= ['white', 'blue', 'black', 'red', 'green', 'yellow'].freeze
end
end
如果它是一个真正的全局常数(但是要避免这种性质的全局常数),您还可以考虑put
config/initializers/my_constants中的顶级常量。比如Rb。
从Rails 4.2开始,您可以使用配置。x属性:
# config/application.rb (or config/custom.rb if you prefer)
config.x.colours.options = %w[white blue black red green]
config.x.colours.default = 'white'
将以以下方式提供:
Rails.configuration.x.colours.options
# => ["white", "blue", "black", "red", "green"]
Rails.configuration.x.colours.default
# => "white"
加载自定义配置的另一种方法:
# config/colours.yml
default: &default
options:
- white
- blue
- black
- red
- green
default: white
development:
*default
production:
*default
# config/application.rb
config.colours = config_for(:colours)
Rails.configuration.colours
# => {"options"=>["white", "blue", "black", "red", "green"], "default"=>"white"}
Rails.configuration.colours['default']
# => "white"
在Rails 5、6和7中,除了config.x,您还可以直接使用配置对象进行自定义配置。但是,它只能用于非嵌套配置:
# config/application.rb
config.colours = %w[white blue black red green]
它将以以下方式提供:
Rails.configuration.colours
# => ["white", "blue", "black", "red", "green"]
Rails 6.1引入了可以简化YML配置的共享组:
# config/colours.yml
shared:
options:
- white
- blue
- black
- red
- green
default: white