Question

我有两个简单的模型，我试图在它们之间创建简单的OneToMany，只要我是新手使用这个库我不能使用库文档，我的主要模型是：

@Table(database = AppDatabase.class)
public class ModelChannelPosts extends BaseModel {
    @PrimaryKey
    private int id;

    @Column
    private String channelId;

    @Column
    private List<ModelVideos> channel_video_containers;

    @Column
    private String createdAt;

    @Column
    private String updatedAt;


    public ModelChannelPosts() {
    }

    @OneToMany(methods = {OneToMany.Method.ALL}, variableName = "channel_video_containers")
    public List<ModelVideos> getVideos() {
        if (channel_video_containers == null || channel_video_containers.isEmpty()) {
            channel_video_containers = new Select()
                    .from(ModelVideos.class)
                    .where(ModelVideos_Table.channelId.eq(id))
                    .queryList();
        }
        return channel_video_containers;
    }

    ...
}

且有许多ModelVideos，然后ModelVideos属于ModelChannelPosts：

@Table(database = AppDatabase.class)
public class ModelVideos extends BaseModel {

    @PrimaryKey
    private int                    id;

    @Column
    private String                 fileName;

    @Column
    private String                 videoLength;

    @Column
    private int                    channelId;

    public ModelVideos() {
    }

    ...
}

ModelChannelPosts_Table文件model.channel_video_containers中的

未知，我收到此错误：

Error:(168, 48) error: <identifier> expected

我如何为他们实施OneToMany？（在channel_video_containers上的ModelChannelPosts和channelId上的ModelVideos之间建立关联？

Answer 1

不知道您使用的是哪个版本的DBFlow，但将@ModelContainer注释添加到ModelChannelPosts可能会对您有所帮助

Answer 2

您可以通过从以下代码段中删除“@Column”来再次检查：

@Column
private List<ModelVideos> channel_video_containers;

注意：您可能会看到channel_video_containers没有setter的错误，因此请创建一个。

并在ModelVideos中放入一个外键，因为许多ModelVideos可以属于单个ModelChannelPosts。 e.g

在ModelVideos类

中

@Column
@ForeignKey(saveForeignKeyModel = false)
ModelChannelPosts modelChannelPosts;

休息看起来不错。我在脑海中记住DBFlow = 4.0.0-beta3的版本（现在是最新的）

Answer 3

这可能会迟到，但对其他开发者来说会有所帮助。一对多关系就像这样

@Table(database = AppDatabase.class)
public class ModelChannelPosts extends BaseModel {

    @PrimaryKey
    private int id;

    @Column
    private String channelId;

    private List<ModelVideos> channel_video_containers;

    @Column
    private String createdAt;

    @Column
    private String updatedAt;


    public ModelChannelPosts() {
    }

    @OneToMany(methods = {OneToMany.Method.ALL}, variableName = "channel_video_containers")
    public List<ModelVideos> getVideos() {
        if (channel_video_containers == null || channel_video_containers.isEmpty()) {
            channel_video_containers = new Select()
                    .from(ModelVideos.class)
                    .where(ModelVideos_Table.modelChannelPosts_id.eq(id))
                    .queryList();
        }
        return channel_video_containers;
    }

    ...
}

和ModelVideos类就像

@Table(database = AppDatabase.class)
public class ModelVideos extends BaseModel {

    @PrimaryKey
    private int id;

    @Column
    private String fileName;

    @Column
    private String videoLength;

    @Column
    private int channelId;

    @ForeignKey(stubbedRelationship = true)
    ModelChannelPosts modelChannelPosts;

    public ModelVideos() {
    }

    ...
}

Android使用DBFlow

3 个答案: