在 Ruby/Rails 模型/控制器中引用关联/属性时 *、self.* 和 @* 之间的差异 [英] Differences between *, self.* and @* when referencing associations/attributes in Ruby/Rails Models/Controllers

问题描述

假设 Rails 模型具有持久性/非持久性属性，引用它们的最佳实践是什么?如果您查看公开可用的代码，则会使用不同的模式.

Assuming a Rails Model with persistent / non-persistent attributes, what is the best practice regarding referencing them? If you look at code publicly available, different patterns are used.

例如，如果您有从一个模型到另一个模型的关联.使用 self.association_name 和 @association_name 有什么区别?.什么是更可取的方法?

For instance, if you have an association from one model to another. What is the difference between using self.association_name and @association_name?. What is the preferable way?

与在模型中使用 attr_accessor :attr 定义的非持久属性相同.您可以使用 self.attr 和 @attr 这两种方法来引用它们.什么是更可取的方法?

Same as with non-persistent attributes defined with attr_accessor :attr in Models. You can reference them with both approaches, self.attr and @attr. What is the preferable way?

推荐答案

self.x/self.x=y are alwaysem> 方法调用.

self.x/self.x=y are always method calls.

(self.x 只是 self.__send__(:x) 的糖，而 self.x = y 只是糖self.__send__(:x=, y))

(self.x is just sugar for self.__send__(:x) and self.x = y is really just sugar for self.__send__(:x=, y))

@x，另一方面，仅指一个实例变量.

@x, on the other hand, only refers to an instance variable.

使用 @x 将不能用于 AR 关联，因为 AR 只定义了 x/x=(它们是方法em>) 因为它的神奇操作.(AR 本质上只是通过这些方法捕获"意图访问，并通过它自己的内部数据结构路由，这些数据结构与任何类似命名的实例变量无关.)

Using @x will not work with AR associations as AR only defines x/x= (which are methods) for its magical operation. (AR essentially just "captures" intent access through these methods and routes through its own internal data structures which are unrelated to any similar-named instance variables.)

attr_accessor 允许双向访问" 因为且仅仅因为它使用同名的实例变量作为它的支持(它必须将值存储在某处).考虑 attr_accessor :x 等价于:

attr_accessor allows "accessing both ways" because and only because it uses the same-named instance variable as it's backing (it has to store the value somewhere). Consider that attr_accessor :x is equivalent to:

def x; @x; end
def x= (y); @x = y; end

快乐编码.

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