设计包含对象列表的DTO

Question

Suppose I have the following domain models:

Project                Task
    - Id                   - Id
    - Name                 - Name
    - List<Task>           - Project

Projects have many Tasks, and Tasks have one Project.

Now suppose I want to create a TodoListDTO data transfer object. My original thought was to just do this:

TodoListDTO
    - List<Project>

Seems simple. Then I have access to the List of Tasks within each Project. Then I read in several places that DTOs should be as flat as possible. But how would I model that without using complex objects?

Instead of TodoListDTO, I could have a ProjectDTO that looks something like:

ProjectDTO
    - ProjectId
    - Name
    - List<TaskId>
    - List<TaskName>

But having separate lists of TaskIds and TaskNames seems inconvenient, and I don't see how that's any better than just having a List property on the ProjectDTO.

What's a good way to handle this?

Answer 1

Another thing you could do is create another domain model of

ProjectTask
    - ProjectId
    - ProjectName
    - TaskId
    - TaskName

This could help with the one-to-many relationship (also allowing many-to-many) and side stepping the confusing circluar project->task->Project->task structure. From here you can have your API client group all ProjectTasks by projectId and handle it that way.

This being said, I think your original way is fine, but here is an alternative.

Answer 2

Your previous classes were simple enough and the standard way of doing it. You would make a Context class that would keep a list of Projects and Tasks. A total of three classes.