CODEWITHSUNDEEP
swiftfilterhigher-order-functions
Swifty
Swifty

Reputation: 905

Filter an array of objects based on field name

Consider an object, Notification, with the following properties:

id: String
body: String
repeats: Bool

and consider an array of Notifications, notifications:

let notifications = [Notification(id: "1", body: "body1", repeats: false),
                     Notification(id: "2", body: "body2", repeats: false),
                     Notification(id: "3", body: "body3", repeats: true)]

How can I use the higher-order filter() function to retrieve an array of Strings corresponding to each id?

In other words, I would like to write a filter() closure to which I pass my notifications and the resulting output is:

["1", "2", "3"]

Therefore, my filter comparison operator should be based on the property name. Is this achievable?

Upvotes: 1

Views: 154

Answers (1)

rmaddy
rmaddy

Reputation: 318774

filter is not the appropriate tool here. filter would be for returning a subset of the notifications based on some criteria (such as only repeating notifications, for example).

You want map which is used to transform data.

let idList = notifications.map { $0.id }

You can combine these as needed. Let's say you wanted the list of ids for the repeating notifications.

let ids = notifications.filter { $0.repeats }.map { $0.id }

Upvotes: 4

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