RealmSwift: Convert Results to Swift Array

问题

What I want to implement:

class func getSomeObject() -> [SomeObject]? {
    let objects = Realm().objects(SomeObject)

    return objects.count > 0 ? objects : nil
}

How can I return object as [SomeObject] instead if Results?

回答1:

Weird, the answer is very straight forward. Here is how I do it:

let array = Array(results) // la fin

回答2:

If you absolutely must convert your Results to Array, keep in mind there's a performance and memory overhead, since Results is lazy. But you can do it in one line, as results.map { $0 } in swift 2.0 (or map(results) { $0 } in 1.2).

回答3:

I found a solution. Created extension on Results.

extension Results {
    func toArray<T>(ofType: T.Type) -> [T] {
        var array = [T]()
        for i in 0 ..< count {
            if let result = self[i] as? T {
                array.append(result)
            }
        }

        return array
    }
}

and using like

class func getSomeObject() -> [SomeObject]? {
    let objects = Realm().objects(SomeObject).toArray(SomeObject) as [SomeObject]

    return objects.count > 0 ? objects : nil
}

回答4:

With Swift 4.2 it's as simple as:

extension Results {
  func toArray() -> [Element] {
    return compactMap {
      $0
    }
  }

All the needed generics information is already a part of Results which we extend.

回答5:

Swift 3

extension Results {
    func toArray<T>(ofType: T.Type) -> [T] {
        var array = [T]()
        for i in 0 ..< count {
            if let result = self[i] as? T {
                array.append(result)
            }
        }

        return array
    }
}

Usage

class func getSomeObject() -> [SomeObject]? {
   let defaultRealm = try! Realm()
    let objects = defaultRealm.objects(SomeObject.self).toArray(ofType : SomeObject.self) as [SomeObject]

    return objects.count > 0 ? objects : nil
}

Alternative : Using generics

class func getSomeObject() -> [T]? {
        let objects = Realm().objects(T.self as! Object.Type).toArray(ofType : T.self) as [T]

        return objects.count > 0 ? objects : nil
}

回答6:

This an another way of converting Results into Array with an extension with Swift 3 in a single line.

extension Results {
    func toArray() -> [T] {
        return self.map { $0 }
    }
}

For Swift 4 and Xcode 9.2

extension Results {
    func toArray<T>(type: T.Type) -> [T] {
        return flatMap { $0 as? T }
    }
}

With Xcode 10 flatMap is deprecated you can use compactMap for mapping.

extension Results {
    func toArray<T>(type: T.Type) -> [T] {
        return compactMap { $0 as? T }
    }
}

回答7:

it's not a good idea to convert Results to Array, because Results is lazy. But if you need try this:

func toArray<T>(ofType: T.Type) -> [T] {
    return flatMap { $0 as? T }
}

but better way is to pass Results wherever you need. Also you can convert Results to List instead of Array.

List(realm.objects(class))

if the first func is not working you can try this one:

var refrenceBook:[RefrenceProtocol] = []
let faceTypes = Array(realm.objects(FaceType))
refrenceBook = faceTypes.map({$0 as FaceType})

回答8:

I'm not sure, if there is any efficient way to do this.

But you can do it by create a Swift array and append it in the loop.

class func getSomeObject() -> [SomeObject]? {
    var someObjects: [SomeObject] = []
    let objects = Realm().objects(SomeObject)
    for object in objects{
        someObjects += [object]
    }
    return objects.count > 0 ? someObjects : nil
}

If you feel it's too slow. I recommend you to pass around Realm Results object directly.

回答9:

extension Results {
    var array: [Element]? {
        return self.count > 0 ? self.map { $0 } : nil
    }
}

So, you can use like:

Realm().objects(SomeClass.self).filter("someKey ENDSWITH %@", "sth").array

回答10:

Solution for Swift 4, Realm 3

extension Results {
    func toArray<T>(ofType: T.Type) -> [T] {
        let array = Array(self) as! [T]
        return array
    }
}

Now converting can be done as below

let array = Realm().objects(SomeClass).toArray(ofType: SomeClass.self)

来源：https://stackoverflow.com/questions/31100011/realmswift-convert-results-to-swift-array