Swift: Two arrays - using value in one to get corresponding value from a second array

Question

I'm pulling out data from two Firebase JSON trees. The data from these trees are downloaded into two arrays. "users" and "activities"

the user array is structured

  ▿ Shoota.Userdata #0
    - userId: "NhZZGwJQCGe2OGaNTwGvpPuQKNA2"
    - name: "Christian"
    - city: "Oslo"
    - country: "Norway"
    - profileImage: "https://firebasestorage.googleapis.com/v0/b/shoota-179610.appspot.com/o/profile_image%2FA176B8AD-EF7D-4C8F-BA7C-06B538795E9D?alt=media&token=025d8d1a-b610-4525-a154-73300599d84c"

the activity array is structured:

▿ Shoota.Activity #0
  - _userId: "NhZZGwJQCGe2OGaNTwGvpPuQKNA2"
  - _name: "Test"
  - _type: "Pheasent"
  - _weapon: "Browning 12 CAL"
  - _kills: "12"
  - _sightings: "100"
  - _note: "Great day of hunting"

This data is used to populate a UITableView. What is the most efficient way to get the corresponding "profileImage" from "users" where Activity._userId = users.userId?

check this out: [filtering array in swift](https://stackoverflow.com/questions/31824810/filtering-array-in-swift) — zombie, Nov 05 '17 at 19:56
See that `userId`? use that as a key in a dictionary of structs that contains your data. — Paulw11, Nov 05 '17 at 19:59
When you load the Shoota.Userdata array, don’t put that data into an array, put it in a dictionary where the key is the userId. Then when you are reading your second array you can easily get the user data simply by accessing the dictionary using the userId value — Paulw11, Nov 05 '17 at 20:17

score 0 · Answer 1 · answered Nov 05 '17 at 20:17

0

The only way is iterating over elements. But if this is frequent operation, its better to make it extansion for Array of Users. The above code makes extension only for Arrays of Users.

struct User{
    var userId: String
    var profileImage: URL
}

extension Array where Element == User {
    func getImage(forId id: String) -> User?{
        return self.first { (user) -> Bool in
            user.userId == id
            }
    }
}

and use it: user.getImage(forId: activity._userId)

or, if don't want any extensions, just use:

users.first { (user) -> Bool in
            user.userId == activity._userId
            }

answered Nov 05 '17 at 20:17

Максуд Даудов

521
5
17

Or put the user data into a dictionary instead of an array – Paulw11 Nov 05 '17 at 20:18
@Максуд: I like the idea of an extension. Would you store that in a separate extension swift file? – Chris_1983_Norway Nov 05 '17 at 20:35
@Chris_1983_Norway, could be. But in this case, I think, its better to store that in file you describe User – Максуд Даудов Nov 05 '17 at 20:46
@Chris_1983_Norway if answer is right for you, set it right answer – Максуд Даудов Nov 08 '17 at 09:20

score 0 · Accepted Answer · answered Nov 08 '17 at 23:24

This is how I finally solved the issue.

let filteredUsers = userdataArray.filter {$0.userId == userId}
    if filteredUsers.count > 0 {
        let profileImageURL = filteredUsers.first!.profileImage
        profileName = filteredUsers.first!.name
        cell.profileImageView.kf.setImage(with: URL.init(string:profileImageURL))
    } else {
        cell.profileImageView.image = UIImage(named: "profile_image_placeholder")
    }

Swift: Two arrays - using value in one to get corresponding value from a second array

2 Answers2