在运行时在模块/命名空间中创建一个类

Question

在运行时创建一个类的过程如下：

klass = Class.new superclass, &block
Object.const_set class_name, klass

例子：

class Person
  def name
    "Jon"
  end
end

klass = Class.new Person do
  def name
    "#{super} Doe"
  end
end

Object.const_set "Employee", klass

puts Employee.new.name # prints "Jon Doe"

现在，假设您有一个名为 Company 的模块：

module Company
end

您如何在 Company 模块/命名空间中在运行时创建 Employee 类，以便以下产生相同的结果？

puts Company::Employee.new.name # prints "Jon Doe"

Answer 1

你已经拥有了所有必要的部分：

class Person
  def name
    "Jon"
  end
end

klass = Class.new Person do
  def name
    "#{super} Doe"
  end
end

module Company
end

Company.const_set "Employee", klass

puts Company::Employee.new.name # prints "Jon Doe"

Company.constants.grep(/Emp/)
#=> [:Employee]

Answer 2

比你想象的要容易:)

Company.const_set "Employee", klass

当您在Object 上设置某些内容时，它会变成全局的，因为，嗯，一切都是Object。但是您可以对每个类/模块执行const_set。请记住，模块/类只是常量。所以，Company::Employee 是常量Employee 中的常量Company。很简单:)

完整代码：

class Person
  def name
    "Jon"
  end
end

klass = Class.new Person do
  def name
    "#{super} Doe"
  end
end

module Company
end

Company.const_set "Employee", klass

Company::Employee.new.name # => "Jon Doe"