Hi,

I am relatively new to swift and I am making an app where there is the following data structure:

An excercise can contain multiple stages and each stage can be one of two types. One type is a count down timer, the other a tap counter, and possibly in the future at most 3 more types will be added, that won't have to store many new attributes.

I am using core data and I have everything working regarding adding the stages, but I was wondering if you would create a separate entity for each type of stage, or just have one entity for the stages like I have now where the unused attributes for the particular type (for instance tap count when it's a count down timer) are left empty. These stages are then related in a many to one relationship with the practice.

Or is there a better solution? Since I am relatively new I would like to avoid unnecessary complexity, but would still like to make an appstore worthy app that could grow in the future.

Best regards,

Florian

Florian wrestles with data structures in his exercise application:

An excercise can contain multiple stages and
each stage can be one of two types.
One type is a count down timer, the other a tap counter, ... snip ... would [you] create a separate entity for each type of stage, or just have one entity for the stages?

It seems you defined a one-to-many relationship. One Exercise object might contain many Stages.

From your description, a Stage object might contain different properties. That is, one type of Stage might have a Counter property collecting repetitions. (Perform 15 Push-Ups.) Another Stage object instead will have a Timed property containing the value indicating how long a Stage should be performed. (Hold a plank position for 90 seconds.)

Protocols

I think this is where the power of Protocols may help. Map your two Stage objects and determine what is similar to both. This might form the basis of your Stage protocol.

Your Exercise object will contain an array of objects that define the particular goals of that exercise. Each object in the array should conform to your Stage protocol.

This will allow you to build views using ForEach and list all the Stages for an exercise regardless of some of the design differences. Additionally, you should be able to add more Stage types to your appliction without much change, as long as the new objects conform to your Stage protocol.

Using protocols, you can enforce the similarities between Exercise goals, and eliminate the need to define properties that would be unused because of its Type.

Thank you very much for your responses, I just wanted to confirm something about the setup in Core Data:

Excercise has a one to many relationship with Stage and stage is an abstract entity

The entitities TimerStage and CounterStage have set Stage as their parent entity, but don't have relationships themselves

Is this correct? Or should Stage not have the relationships, and should TimerStage and CounterStage have the relationships?

If I remember correctly Stage should have the relationship.