Realm-cocoa: How to store an array of strings in Realm?

Created on 24 Jun 2016 · 9Comments · Source: realm/realm-cocoa

I feel silly having to ask this question, but what's the best way to store an array or collection of strings? Without thinking, I originally tried to use a Swift array which crashed the app and I've also tried List<String> but because String is not a Realm type, it does not work. Suggestions?

Just looking for a push in the right direction.

Cheers

T-Feature

Source

luna-kx

👍7

Most helpful comment

For some reason it doesn't work for me, I'm using ObjectMapper:

Transform

// Transform Array to Realm.List -> Primitives
func arrayToList<T>() -> TransformOf<List<T>, [T]> {
  return TransformOf(
    fromJSON: { (value: [T]?) -> List<T> in
      let result = List<T>()
      if let value = value {
        result.append(objectsIn: value)
      }
      return result
    },
    toJSON: { (value: List<T>?) -> [T] in
      var results = [T]()
      if let value = value {
        results.append(contentsOf: Array(value))
      }
      return results
  })
}

class Foo: Object, Mappable {

var images = List<String>()

public func mapping(map: Map) {
  images <- (map["images.original"], arrayToList())
  print(images) // <- At this point it has a value
...
}

But when I fetch those objects from Realm, images is always empty, any idea??

robertofrontado on 23 Jan 2018

👍3

All 9 comments

Found this: http://stackoverflow.com/a/31730894/5236819

Really wish Realm supported primitive types. :) Thanks anyways

luna-kx on 24 Jun 2016

👍1

For others finding this, we're tracking it in #1120.

jpsim on 27 Jun 2016

👍1

We now support list of primitives. See https://realm.io/blog/realm-cocoa-reaches-3-0/

bmunkholm on 19 Jan 2018

👍3

Thanks

amirpervaiz086 on 22 Jan 2018

For some reason it doesn't work for me, I'm using ObjectMapper:

Transform

// Transform Array to Realm.List -> Primitives
func arrayToList<T>() -> TransformOf<List<T>, [T]> {
  return TransformOf(
    fromJSON: { (value: [T]?) -> List<T> in
      let result = List<T>()
      if let value = value {
        result.append(objectsIn: value)
      }
      return result
    },
    toJSON: { (value: List<T>?) -> [T] in
      var results = [T]()
      if let value = value {
        results.append(contentsOf: Array(value))
      }
      return results
  })
}

class Foo: Object, Mappable {

var images = List<String>()

public func mapping(map: Map) {
  images <- (map["images.original"], arrayToList())
  print(images) // <- At this point it has a value
...
}

But when I fetch those objects from Realm, images is always empty, any idea??

robertofrontado on 23 Jan 2018

👍3

Please don't ask questions that are only tangentially related to the initial question on an issue that's been closed for months.

Your problem appears to be due to the fact that you're allocating a new List<T> and assigning that to your property rather than _mutating_ the property. Our documentation recommends that you declare your List<T> properties using let rather than var so the compiler will prevent you from making this mistake.