在Grails中访问关系表 [英] Access Relationship Table in Grails
问题描述
class文章{
字符串名称
字符串国家
static hasMany = [标签:标签]
静态约束= {
}
}
类标签{
字符串名称
static belongsTo =帖子
static hasMany = [帖子:帖子]
static constraints = {
}
String toString()
{
$ {TypeName}
}
}
Grails在数据库中创建另一个表,即Posts_Tags。
我的要求是:
例如1发布有3个标签。
因此,在Posts_Tags表中有3行。
如何直接在我的代码中访问表Posts_Tags,以便我可以操作数据或添加如果你想访问连接表( Posts_Tags $
PostTag
域类。然后,将 Post
和 Tag
之间的多关系拆分为2个一对多关系(一个来自发布
到邮政标签
和一个从标签
到 PostTag
)。 这是综合示例,介绍如何执行映射并向连接表添加属性 - 在本例中 Membership
是连接表。
I have the following domains classes:
class Posts{
String Name
String Country
static hasMany = [tags:Tags]
static constraints = {
}
}
class Tags{
String Name
static belongsTo = Posts
static hasMany = [posts:Posts]
static constraints = {
}
String toString()
{
"${TypeName}"
}
}
Grails creates an another table in the database i.e. Posts_Tags.
My requirement is:
E.g. 1 post has 3 tags. So, in the Posts_Tags table there are 3 rows.
How can I access the table Posts_Tags directly in my code so that I can manipulate the data or add some more fields to it.
If you want to access the join table (Posts_Tags
) directly, or add properties to it, then you must define it as a separate PostTag
domain class. You then split your many-many relationship between Post
and Tag
into 2 one-to-many relationships (one from Post
to PostTag
and one from Tag
to PostTag
).
Here's a comprehensive example of how to perform the mapping and add properties to the join table - in this example Membership
is the join table.
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