[SOLVED] Filter array of items by enum property with associated value

Filter array of items by enum property with associated value

class MyClass: Decodable {

    let title: String?
    let type: MyClass.MyType?

    enum MyType {
        case article(data: [Article])
        case link(data: [LinkTile])
        case none
    }
}

I would like to filter an array of MyClass items, so the filtered array won't contain instances with type .none

let filteredArray = array.filter { $0.type != .none } // this doesn't work

Solution

Unfortunately, you can't use == with enums with associated values. You need to use pattern matching, but that needs to be done in a switch or if statement.

So, that leads to something ugly like this:

let filteredArray = array.filter { if case .none = $0.type! { return false }; return true }

Notes:

You can't name your enum Type because it conflicts with the built-in Type. Change it to something like MyType.
It is terribly confusing to use none as a case in a custom enum because it gets confused (by the humans) with none in an optional. This is made worse by the fact that your type property is optional. Here I have force unwrapped it, but that is dangerous of course.

You could do:
```
if case .none? = $0.type
```
This would match the none case explicitly and treat nil as something you want to keep.

To filter out nil and .none, you could use the nil coalescing operator ??:
```
if case .none = ($0.type ?? .none)
```
I would suggest declaring type as MyClass.MyType instead of MyClass.MyType?.