alias_method_chain是否与alias_method同义？

问题描述

如果这两个方法只是同义词，为什么人们会麻烦写其他字符 _chain ？

If these two methods are simply synonyms, why do people go to the trouble of writing the additional characters "_chain"?

推荐答案

否。 alias_method 是Ruby的标准方法。 alias_method_chain 是一个Rails附加组件，旨在简化以下常用操作：将旧方法别名为新名称，然后将新方法别名为原始名称。因此，例如，如果您要使用新功能 new_feature 创建新版本的方法方法，则以下两个代码示例是等效的：

No. alias_method is a standard method from Ruby. alias_method_chain is a Rails add-on designed to simplify the common action of aliasing the old method to a new name and then aliasing a new method to the original name. So, if for example you are creating a new version of the method method with the new feature new_feature, the following two code examples are equivalent:

alias_method :method_without_new_feature, :method
alias_method :method, :method_with_new_feature

和

alias_method_chain :method, :new_feature

---

编辑

这是一个假设的示例：假设我们有一个Person类，其方法为 rename 。它所做的只是取一个像 John Doe的字符串，在空格上分割，然后将部分分配给first_name和last_name。例如：

---

EDIT

Here is a hypothetical example: suppose we had a Person class with a method rename. All it does is take a string like "John Doe", split on the space, and assign parts to first_name and last_name. For example:

person.rename("Steve Jones")
person.first_name  #=> Steve
person.last_name   #=> Jones

现在我们遇到了问题。我们一直在获取不正确大写的新名称。因此，我们可以编写一个新方法 rename_with_capitalization 并使用 alias_method_chain 来解决此问题：

Now we're having a problem. We keep getting new names that aren't capitalized properly. So we can write a new method rename_with_capitalization and use alias_method_chain to resolve this:

class Person
  def rename_with_capitalization(name)
    rename_without_capitalization(name)
    self.first_name[0,1] = self.first_name[0,1].upcase
    self.last_name[0,1] = self.last_name[0,1].upcase
  end

  alias_method_chain :rename, :capitalization
end

现在，旧的重命名称为不带大写字母的重命名，而重命名和大写字母的名称为重命名。例如：

Now, the old rename is called rename_without_capitalization, and rename_with_capitalization is rename. For example:

person.rename("bob smith")
person.first_name  #=> Bob
person.last_name   #=> Smith

person.rename_without_capitalization("tom johnson")
person.first_name  #=> tom
person.last_name   #=> johnson

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