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What is best way in swift to get objects of specific type. e.g

protocol Fruit {
    func setColor()

}

class Orange:NSObject, Fruit {
    func setColor() {

    }
}

class Apple:NSObject, Fruit {
    func setColor() {
    }
}


class MyClass {

    var fruits:[Fruit]? // get from data base

    //here how to get fruits only of type Orange. i.e. Array of oranges

}

Here one way is I can put "for in" loop and check type of each object and then can add it in new array.

But is there any other swifty way to do?

EDIT:

Below works for me. Is there any other way to do?

  var oranges: [Orange] = []
   for orange in fruits {

   if let myOrange = orange as? Orange {
        oranges.append(myOrange)
     }
   }
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5
  • 1
    It's bad practice to write setters and getters in Swift. Just use public properties. That's what they're there for. Commented Feb 1, 2017 at 4:04
  • 1
    Also no need to subclass NSObject unless you are planning to conform it to NSCoding otherwise you should use structs instead of classes. Commented Feb 1, 2017 at 4:54
  • 1
    bad naming for the loop, would be much better for fruit in fruits and then if let orange = fruit as? Orange { Commented Feb 1, 2017 at 5:02
  • btw just add a computed property to MyClass var oranges: [Orange] { return fruits.flatMap{$0 as? Orange} } Commented Feb 1, 2017 at 5:11
  • 1
    Java is bad for a reason... setters and getters make NO SENSE 99% of the time... it's just extra work for you so you have the feeling of 'encapsulation safety' but really it's not doing a thing for your code! Commented Feb 1, 2017 at 6:49

1 Answer 1

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2

If you simply want to iterate over these in a for loop, just add a where clause:

for fruit in fruits where fruit is Orange {

}

If you want a filtered array (still of type [Fruit]) to store for future use, use filter:

let oranges = fruits.filter{ $0 is Orange }

If you want a filtere array (of type [Orange]) to store for future use, user flatMap:

let oranges = fruits.flatMap{ $0 as? Orange }
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5 Comments

I am getting error for filter option - Cannot convert value of type '[Fruit]' to expected argument type '[Orange]'
@user364765 Did you unwrap fruits?
let oranges = fruits.flatMap { $0 as? Orange }
@user3647675 Oh yeah, if you want to get an [Orange] back, you'll need to actually do the cast, as vacawama suggests.
@user3647675 can you update your code now to show the new error and such?

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