Swift 4: Keeping the same order when parsing a JSON

Question

I need to show a list of addresses in my app while keeping the same order as the response JSON. It looks something like this:

{
"addresses": {
    "e5fdb5ba-7afb-11e8-bead-43321d1a8905": {
        "contact": "Name1",
        "zipCode": "06100"
    },
    "1495b580-7afc-11e8-bead-9f4049791561": {
        "contact": "Name2",
        "zipCode": "06100"
    },
    "e5fdb5ba-7afb-11e8-bead-43321d1a8905": {
        "contact": "Name3",
        "zipCode": "06100"
    },
    "1495b580-7afc-11e8-bead-9f4049791561": {
        "contact": "Name4",
        "zipCode": "06100"
    }
  } 
}

But when I parse the response using

JSONSerialization.jsonObject(with: data, options: [])

The order of the addresses gets all mixed up. Is there a way to keep the exact same order as the JSON?

It's a dictionary, it has no order and order is irrelevant. If order is important, use an array. — rmaddy, Jun 28 '18 at 22:34
Would the array need to come directly from the backend or is there a way to create one using the example above? — MVZ, Jun 28 '18 at 22:36
rmaddy is right. But, could you find back the ordering in one of the addresses' fields, for example `name`? — meaning-matters, Jun 28 '18 at 23:12

score 2 · Answer 1 · answered Jun 28 '18 at 23:13

as rmaddy says in their comment, the JSON you posted is a dictionary. Dictionaries are inherently unordered, so the order you get from the back-end is not guaranteed either. Some server implementations may give a consistent order and some may not.

If you want a certain order you will need to change the back-end system to use an array rather than a dictionary.

If you have no control of the client side and still want to preserve the order of the keys from the JSON, you will probably have to parse the JSON yourself manually, build an array of the keys, and then use those keys to fetch the items from the dictionary in that order.

score 1 · Answer 2 · answered Jun 29 '18 at 01:19

If the order of your data is important you should put it into an Array, not a Dictionary (which is inherently without order but with quick keyed access as others have noticed). Please change your backend accordingly and ask another question if it does not work.

Swift 4: Keeping the same order when parsing a JSON

2 Answers2

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