我知道在SQL中,要将两个不同的对象相互关联,一个对象在一个表中使用主键,另一个表中使用外键。因为FirebaseDatabase使用JSON/NoSQL这是不可能的。如果我有两个对象,分别是UserPostEntity和PostEntity,那么一旦用户发出post/comment,我将如何将UserPostEntity与PostEntity关联起来,PostEntity将如何使用用户发出的post/comment自动更新?
用户实体对象:

import Foundation

    class UserEntity{

        var userID: String
        var postedComment: String
        var postDate: String
        var postID: PostEntity

        init(userID: String, postedComment: String, postDate: String, postID: PostEntity){
            self.userID = userID
            self.postedComment = postedComment
            self.postDate = postDate
            self.postID = postID
        }
    }

PostEntity对象:
import Foundation

class PostEntity{

    var userID: String
    var postID: String
    var postedComment: String
    var postDate: String

    init(userID: String, postID: String, postedComment: String, postDate: String){
        self.userID = userID
        self.postID = postID
        self.postedComment = postedComment
        self.postDate = postDate
    }
}

最佳答案

如果你能在Firebase中构建你的数据会更好。以下链接提供了在Firebase中构造数据的良好直觉:
https://firebase.googleblog.com/2013/04/denormalizing-your-data-is-normal.html
https://www.firebase.com/docs/web/guide/structuring-data.html
您可以定义user表和posts如下:

user{
    "u1" {

         userName : "abc",
         posts {
              p1 : true,
              p2 : true
          }
        },

        "u2" {

         userName : "def",
         posts {
              p3 : true,
              p4 : true
          }
        }

  }

  post{
        "p1"{
            userId : "u1",
            postComment : "hello ios",
            postDate : "1467570919"
            },
        "p2"{
            userId : "u1",
            postComment : "ios",
            postDate : "1467570920"
            },
        "p3"{
            userId : "u2",
            postComment : "hello ios",
            postDate : "1467570921"
            },
        "p4"{
            userId : "u2",
            postComment : "hello ios",
            postDate : "1467570922"
            }
    }

也可以按如下方式创建实体:
class UserEntity{

        var userID: String
        var userName : String
        var posts: Dictionary<String, Bool>?
        var ref : FIRDatabaseReference?

        init(userID: String, userName: String, posts: Dictionary<String, Bool>?){
            self.userID = userID
            self.userName = userName
            self.posts = posts
            self.ref = nil
        }
    }


    class PostEntity{

    var pId: String
    var uId: String
    var postedComment: String
    var postDate: NSTimeInterval
    var ref : FIRDatabaseReference?

    init(pId: String, uId: String, postedComment: String, postDate: NSTimeInterval){
        self.pId= pId
        self.uId = uId
        self.postedComment = postedComment
        self.postDate = postDate
        self.ref = nil
    }
}

此外,您还需要按照post中的回答来构造UserEntityPostEntity实体。
当用户添加新的postposts时,必须将user表的p5 :true属性更新为p5

10-06 05:10