ios - Remove objects with duplicate properties from Swift array

Question

The question here involves removing duplicate objects from an array:

Removing duplicate elements from an array in Swift

I instead need to remove objects that are not themselves duplicates, but have specific duplicate properties such as id.

---

I have an array containing my Post objects. Every Post has an id property.

Is there a more effective way to find duplicate Post ID's in my array than

for post1 in posts {
    for post2 in posts {
        if post1.id == post2.id {
            posts.removeObject(post2)
        }
    }
}

Answer 1

I am going to suggest 2 solutions.

Both approaches will need Post to be Hashable and Equatable

Conforming Post to Hashable and Equatable

Here I am assuming your Post struct (or class) has an id property of type String.

struct Post: Hashable, Equatable {
    let id: String
    var hashValue: Int { get { return id.hashValue } }
}

func ==(left:Post, right:Post) -> Bool {
    return left.id == right.id
}

Solution 1 (losing the original order)

To remove duplicated you can use a Set

let uniquePosts = Array(Set(posts))

Solution 2 (preserving the order)

var alreadyThere = Set<Post>()
let uniquePosts = posts.flatMap { (post) -> Post? in
    guard !alreadyThere.contains(post) else { return nil }
    alreadyThere.insert(post)
    return post
}