references

作者: 栋栋晓 | 来源:发表于2016-02-01 21:59 被阅读19次

一个帮助工具references，用来指明表的外键关系。
create_table :products do |t| t.references :category end
上面的代码会在products表中添加一个外键字段category_id。

create_table :products do |t| t.references :attachment, :polymorphic => {:default =>'Photo'} end

上面的代码不仅会在products表中添加外键字段attachment_id，还会添加attachment_type字段，string类型，默认值是Photo。

references
一个帮助工具references，用来指明表的外键关系。create_table :products do |t|...
References
Effective Kotlin
Representation theory reading li
1. David Vogan's References 2. Jeffrey Adams's References...
Associative References
这个也是重量级的api 。类别里添加属性用到。根据关联policy 确定是否要释放对象如果用copy策略obj要实...
Storyboard References
Storyboard References 关于这个东西，只从storyboard出来之后就一直，团队分工合作冲突...
Initialization and References to
今天读到《C++ Primer》第五版第2.4.1节 References to const 讲到了引用和被引用的...
Reading and References
ReferencesBarnes, David J. and Kolling, Michael, Objects ...
Reading and References
ReferencesDiller, A. Z: An Introduction to Formal Methods...
Reading and References
References Most reference material will be in the form of...
References and Borrowing
1. References Ownership[https://www.jianshu.com/p/b232f2e...

网友评论

本文标题：references

本文链接：https://www.haomeiwen.com/subject/rvbskttx.html

references