在类中，您已经将call定义为一个示例方法，但您将其作为类方法调用。你可以使用def self.call将它变成一个类方法：

class MixPanelService
  def self.call(shop, event_type)
    send(event_type, shop)
  end

  def self.install(shop)
    # do something
  end
  private_class_method :install # ugly :(
end

# Call it like this:
MixPanelService.call(shop, 'install')

但这并不是最好的设计。使用类方法和传递参数很麻烦。你可以使用示例，但仍然有一个类方法来运行一切。看看这个模式：

class MixPanelService
  def self.call(shop, event_type)
    new(shop).call(event_type)
  end

  def initialize(shop)
    @shop = shop
  end

  def call(event_type)
    send(event_type)
  end

  private

  def install
    # Install something on `@shop`. Since it's an instance variable,
    # we don't need to pass it around via params! :)
  end
end

# Call it the same way as before:
MixPanelService.call(shop, 'install')

这是因为module_function不支持这样的私有方法。它将公共示例方法复制为self模块方法，并将其作为私有示例
也许它是更好地比较这种行为在行动中，它取决于你选择你需要什么

# With module_function
module MyModule
  module_function

  def my_public_method
    puts "Hi from public"
    my_private_method
  end

  private

  def my_private_method
    puts "Hi from private"
  end
end

class MyIncludeClass
  include MyModule
end

class MyExtendClass
  extend MyModule
end

MyModule.my_public_method
# Hi from public
# undefined local variable or method `my_private_method' for MyModule:Module (NameError)

MyModule.my_private_method
# undefined method `my_private_method' for MyModule:Module (NoMethodError)

MyIncludeClass.new.my_public_method
# private method `my_public_method' called for #<MyIncludeClass:0x0000000104d766f8> (NoMethodError)

MyIncludeClass.new.my_private_method
# private method `my_private_method' called for #<MyIncludeClass:0x0000000104eb17c0> (NoMethodError)

MyExtendClass.my_public_method
# private method `my_public_method' called for MyExtendClass:Class (NoMethodError)

MyExtendClass.my_private_method
# private method `my_private_method' called for MyExtendClass:Class (NoMethodError)

# With extend self
module MyModule
  extend self

  def my_public_method
    puts "Hi from public"
    my_private_method
  end

  private

  def my_private_method
    puts "Hi from private"
  end
end

class MyIncludeClass
  include MyModule
end

class MyExtendClass
  extend MyModule
end

MyModule.my_public_method
# Hi from public
# Hi from private

MyModule.my_private_method
# private method `my_private_method' called for MyModule:Module (NoMethodError)

MyIncludeClass.new.my_public_method
# Hi from public
# Hi from private

MyIncludeClass.new.my_private_method
# private method `my_private_method' called for #<MyIncludeClass:0x0000000108afa790> (NoMethodError)

MyExtendClass.my_public_method
# Hi from public
# Hi from private

MyExtendClass.my_private_method
# private method `my_private_method' called for MyExtendClass:Class (NoMethodError)

# With class << self syntax
module MyModule
  class << self
    def my_public_method
      puts "Hi from public"
      my_private_method
    end

    private

    def my_private_method
      puts "Hi from private"
    end
  end
end

class MyIncludeClass
  include MyModule
end

class MyExtendClass
  extend MyModule
end

MyModule.my_public_method
# Hi from public
# Hi from private

MyModule.my_private_method
# private method `my_private_method' called for MyModule:Module (NoMethodError)

MyIncludeClass.new.my_public_method
# undefined method `my_public_method' for #<MyIncludeClass:0x0000000103fec6b8> (NoMethodError)

MyIncludeClass.new.my_private_method
# undefined method `my_private_method' for #<MyIncludeClass:0x00000001041929e0> (NoMethodError)

MyExtendClass.my_public_method
# undefined method `my_public_method' for MyExtendClass:Class (NoMethodError)

MyExtendClass.my_private_method
# undefined method `my_private_method' for MyExtendClass:Class (NoMethodError)

# With private_class_method
module MyModule
  def self.my_public_method
    puts "Hi from public"
    my_private_method
  end

  def self.my_private_method
    puts "Hi from private"
  end

  private_class_method :my_private_method
end

class MyIncludeClass
  include MyModule
end

class MyExtendClass
  extend MyModule
end

MyModule.my_public_method
# Hi from public
# Hi from private

MyModule.my_private_method
# private method `my_private_method' called for MyModule:Module (NoMethodError)

MyIncludeClass.new.my_public_method
# undefined method `my_public_method' for #<MyIncludeClass:0x00000001044f1870> (NoMethodError)

MyIncludeClass.new.my_private_method
# undefined method `my_private_method' for #<MyIncludeClass:0x000000010449bfb0> (NoMethodError)

MyExtendClass.my_public_method
# undefined method `my_public_method' for MyExtendClass:Class (NoMethodError)

MyExtendClass.my_private_method
# undefined method `my_private_method' for MyExtendClass:Class (NoMethodError)

这就是我遇到的问题的解决方案。现在一切正常我最终使用了module和self，如下所示：

module MixPanelService
  module_function

  def self.call(shop, event_type)
    send(event_type, shop)
  end

  private

  def self.install(shop)
    # do something
  end

end