Rails Presenters 教程中关于方法的问题

Question

关于我在本教程中看到的几个方法的问题：https://richonrails.com/articles/rails-presenters

特别是：

module ApplicationHelper
    def present(model, presenter_class=nil)
        klass = presenter_class || "#{model.class}Presenter".constantize
        presenter = klass.new(model, self)
        yield(presenter) if block_given?
    end
end

和

class BasePresenter < SimpleDelegator 
    def initialize(model, view)
        @model, @view = model, view
        super(@model)
    end

    def h 
        @view 
    end

end

present 方法是如何工作的？我对它的 arguments 参数感到很困惑，即model, presenter_class=nil 以及整个方法。

我也对model, view 参数感到非常困惑，super(@model) 方法在哪里/是什么？

任何可以解释这些方法的信息都会非常有帮助，因为我过去一直在盯着它看，同时想知道它们到底是如何工作的。

Answer 1

我会试一试。

present 方法接受两个参数，一个模型和一个演示者类。

presenter_class = nil 表示presenter_class 是一个可选参数，如果在调用方法时没有将变量作为该参数传递，则将其设置为nil。

我在代码中添加了 cmets 来逐步解释发生了什么。

# Define the Helper (Available in all Views)
module ApplicationHelper
    # Define the present method, accepts two parameters, presnter_class is optional
    def present(model, presenter_class=nil)
        # Set the presenter class that was passed in OR attempt to set a class that has the name of ModelPresenter where Model is the class name of the model variable
        klass = presenter_class || "#{model.class}Presenter".constantize
        # ModelPresenter is initialized by passing the model, and the ApplicationHelper class
        presenter = klass.new(model, self)
        # yeild the presenter if the rails method block_given?
        yield(presenter) if block_given?
    end
end

Here's another question explaining how yield works

Here's some more info on the rails constantize method

BasePresenter 继承自 SimpleDelegator 类 (documentation)。

class BasePresenter < SimpleDelegator 
    def initialize(model, view)
        # Set the instance variables @model and @view as the two parameters passed to BasePresenter.new
        @model, @view = model, view
        # calls the inherited SimpleDelegator initializer with the @model parameter
        super(@model)
    end

    # An instance method that returns the @view variable that was set on initialization
    def h 
        @view 
    end

end