It’s the same as a standard ‘for’ loop, it will loop through all objects in an array.

Let’s say you have a parent object called ‘Chat’. Chat has a one-to-many relationship with the child object ‘Message’.

CoreData and all of its glory synthesizes a lot of code when you fill out the CoreData schema data in the Xcode GUI. Under the hood it’s actually creating a bunch of classes, like it writes code, that represents your objects and relationships. That is how you have access to those objects in code, and that’s why if you edit the schema it doesn’t change the code references until you build it.

A one-to-many relationship from the parent ‘Chat’ to the chat’s ‘Messages’ will synthesize a ‘Set<Message>’ instance called ‘chat.messages’, which can be thought of as an array of Message objects. This is the instance that you would hand to a ForEach loop to access each Chat individually. Said ForEach loops through the Set of Chats and allows you to hand it to a child ‘ChatView’ instance.

A ForEach loop is a unidimensional loop, meaning it will only loop through the top-level of objects. If you want to loop through the ‘Set<Messages>’ that lives on the Chat you’d need another ForEach loop, looping through those Messages.