YAML中更复杂的继承？ [英] More complex inheritance in YAML?

问题描述

YAML有继承权。我见过的最明显的例子是： http://blog.101ideas.cz/posts/dry-your-yaml-files.html

YAML has inheritance. The most clear example I have ever seen is here: http://blog.101ideas.cz/posts/dry-your-yaml-files.html

我需要更复杂的东西：我需要覆盖对象的对象的属性。这是一个例子：

I need something more complex: I need to override object's object's property. Here is an example:

database: &default
  server:
    ip: 192.168.1.5
    port: 2000
  db_name: test
  user: 
    name: root
    password: root

# database foo differs from default by only its port and user password
foo_database:
  <<: *default
  server:
    port: 2001
  db_name: foo
  user:
    password: foo_root

我想得到这个结果：

foo_database.server.ip -> 192.168.1.5
foo_database.server.port -> 2001
foo_database.db_name -> foo
foo_database.user.name -> root
foo_database.user.password -> foo_root

但如果你这样声明，你会得到这些属性不正确（根据预期值）：

But if you declare like this, you will get these properties incorrect (according to expected values):

foo_database.server.ip -> will be None
foo_database.user.name -> will be None

因为新的服务器对象只有port属性而且它会覆盖整个旧的服务器对象。

because new "server" object has only "port" property and it overrides whole old "server" object.

如何获得我想要实现的继承？

How do I get the kind of inheritance which I want to achieve?

推荐答案

不幸的是，你不能得到你想要实现的那种继承，因为YAML的继承更像是一种合并哈希的形式。

Unfortunately, you can't get the kind of "inheritance" you want to achieve because YAML's "inheritance" is more like a form of "merging hashes".

在你使用 * default 别名时扩展你的配置，你有：

Expanding out your configuration at the point you use the *default alias, you have:

foo_database:
  server:
    ip: 192.168.1.5
    port: 2000
  db_name: test
  user: 
    name: root
    password: root

如果你之后使用具有相同键的哈希值，他们将完全覆盖之前声明的哈希值，留下你（原谅格式化）：

If you use hashes with the same keys afterwards, they will completely overwrite the hashes declared earlier, leaving you with (excuse the formatting):

foo_database:

  server:
    ip: 192.168.1.5
    port: 2000
  db_name: test
  user: 
   name: root
   password: root  

  server:
    port: 2001
  db_name: foo
  user:
    password: foo_root

因此，在您的情况下，似乎由于配置不是完全相同，可能使用锚点和别名来干扰您的配置不是正确的做法。

So, in your case, it would seem that since the config is not exactly the same, DRYing up your configuration using anchors and aliases probably isn't the right approach.

以下关于这个问题的更多参考资料：

More references on this issue below:

• Rake，YAML和继承的构建配置


• 在yaml conf文件中合并哈希值

• Rake, YAML and Inherited Build Configuration
• Merging hashes in yaml conf files

如果你真的想，我想你可以重新配置你的YAML如下所示，以获得你想要的，但在你的情况下，我会说额外的混淆是不值得的：

If you really wanted to, I think you could reconfigure your YAML as below to get exactly what you want, but in your case, I would say the extra obfuscation isn't worth it:

server_defaults: &server_defaults
  ip: 192.168.1.5
  port: 2000

user_defaults: &user_defaults
  name: root
  password: root

database: &default
  server:
    <<: *server_defaults
  db_name: test
  user: 
    <<: *user_defaults

foo_database:
  <<: *default
  server:
    <<: *server_defaults
    port: 2001
  db_name: foo
  user:
    <<: *user_defaults
    password: foo_root

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