GORM ASSOCIATION EXPLANATION

Question

我需要帮助在域类之间创建关联。我有三个域：用户，新闻，评论。用户可以对许多新闻发表很多评论。新闻可以有很多用户的评论。

我在GORM中实现这种关联存在很大问题。

我希望用户能够为新闻项添加评论。评论应该引用制作它的用户。新闻项目应该包含所有评论的列表。

域类：

sqlite3

IntegrationTests包括：

class User {
    String nickName
    String password
    Date dateCreated
    static hasMany = [users : User, comments : Comment]
    static hasOne = [profile : Profile]
    //static belongsTo = [comments : Comment]

    static constraints = {
        profile nullable: true
    }
}

class News {

    String webTitle
    String webPublicationDate;
    String trailText;
    String webUrl;
    String thumbnail;
    String webId;
    static hasMany = [tags : Tag, comments  : Comment]

    static constraints = {
    }
}

class Comment {
    //static belongsTo = [news : News, user : User]
    String content
    int likes
    int disLikes
    Date lastUpdated
    static hasOne = [user: User, news:  News]

    static constraints = {
    }
}

任何帮助将不胜感激

Answer 1

我宁愿稍微更改您的域类：

class User {
    String nickName
    String password
    Date dateCreated
    static hasMany = [users : User, comments : Comment]
    static hasOne = [profile : Profile]

    static constraints = {
        profile nullable: true
    }
}

class Communicate { //because News could possibly create troubles during generating controller or test classes (it's the same as singular and plural)
    String webId; 
    String webTitle
    String webPublicationDate;
    String trailText;
    String webUrl;
    String thumbnail;
    static hasMany = [tags : Tag, comments  : Comment]

    static constraints = {
    }

}

class Comment {
    static belongsTo = [user: User, communicate: Communicate] //read more about it: http://docs.grails.org/latest/ref/Domain%20Classes/belongsTo.html
    String content
    int likes
    int disLikes
    Date lastUpdated

    static constraints = {
    }

}

在这些更改之后，您应该重新创建这些表（如果它仍处于开发阶段，则创建完全删除db。）

此外，通过向评论添加belongsTo语句，您应该修复您的测试（user并且“创建时”将需要“通信”属性：

def comm = new Comment(content: "Hillary cant be president", user:user, communicate:news)