>
>
>
> Sure, but I don’t want to give a dictionary of unknown types: i’m very happy
> to say that my dictionary is
> [String : Codable]
>
> but
> struct Foo : Codable {
> let d: [String : Codable]
> }
>
> doesn’t work; the d inside F is not itself Codable.
>
> That’s strange.
I don’t think it is. I would completely expect Swift to handle a dictionary of
a concrete type: that’s not a heteregenous container then. When you use the
protocol Codable, then it becomes heterogenous, which is the issue.
> We’re actually doing exactly this and it works for us (although we are using
> a concrete Codable type rather than the Codable metatype itself).
>
> Maybe it’s worth filing a bug on Jira
>
> Good luck.
>
>
>>
>>
>> So basically, back to wanting to let the compiler do the work, when I make
>> new structures, while still allowing for heterogenous containers.
>>
>> It’s also possible to give the compiler hints as to what decodes into what.
>> Have you looked at the docs on the Apple foundation page?
>>
>> https://developer.apple.com/documentation/foundation/archives_and_serialization/encoding_and_decoding_custom_types
>>
>> <https://developer.apple.com/documentation/foundation/archives_and_serialization/encoding_and_decoding_custom_types>
>>
>> Geordie
>>
>>
>>
>>
>>
>>
>>
>>
>> Begin forwarded message:
>>
>>
>>> From: Itai Ferber <[email protected] <mailto:[email protected]>>
>>> Subject: Re: [swift-users] dealing with heterogenous lists/dictionary with
>>> Codable
>>
>>> Date: October 19, 2017 at 10:40:28 AM PDT
>>
>>> To: David Baraff <[email protected] <mailto:[email protected]>>
>>> Cc: Geordie Jay <[email protected] <mailto:[email protected]>>, swift-users
>>> <[email protected] <mailto:[email protected]>>
>>>
>>
>>> Why are you stuck? I think the following matches your needs, no?
>>>
>>> import Foundation
>>>
>>> enum MyType : Codable, Equatable {
>>> case int(Int)
>>> case string(String)
>>> case list([MyType])
>>> case dictionary([String : MyType])
>>>
>>> public init(from decoder: Decoder) throws {
>>> // Can be made prettier, but as a simple example:
>>> let container = try decoder.singleValueContainer()
>>> do {
>>> self = .int(try container.decode(Int.self))
>>> } catch DecodingError.typeMismatch {
>>> do {
>>> self = .string(try container.decode(String.self))
>>> } catch DecodingError.typeMismatch {
>>> do {
>>> self = .list(try container.decode([MyType].self))
>>> } catch DecodingError.typeMismatch {
>>> self = .dictionary(try container.decode([String :
>>> MyType].self))
>>> }
>>> }
>>> }
>>> }
>>>
>>> public func encode(to encoder: Encoder) throws {
>>> var container = encoder.singleValueContainer()
>>> switch self {
>>> case .int(let int): try container.encode(int)
>>> case .string(let string): try container.encode(string)
>>> case .list(let list): try container.encode(list)
>>> case .dictionary(let dictionary): try container.encode(dictionary)
>>> }
>>> }
>>>
>>> static func ==(_ lhs: MyType, _ rhs: MyType) -> Bool {
>>> switch (lhs, rhs) {
>>> case (.int(let int1), .int(let int2)): return int1 == int2
>>> case (.string(let string1), .string(let string2)): return string1
>>> == string2
>>> case (.list(let list1), .list(let list2)): return list1 == list2
>>> case (.dictionary(let dict1), .dictionary(let dict2)): return dict1
>>> == dict2
>>> default: return false
>>> }
>>> }
>>> }
>>>
>>> let values: MyType = .list([.int(42), .string("hello!"), .list([.int(9),
>>> .string("hi")]), .dictionary(["zero": .int(0), "one": .int(1)])])
>>> print(values)
>>>
>>> let encoder = JSONEncoder()
>>> let data = try encoder.encode(values)
>>> print(String(data: data, encoding: .utf8)!) // =>
>>> [42,"hello!",[9,"hi"],{"zero":0,"one":1}]
>>>
>>> let decoder = JSONDecoder()
>>> let decoded = try decoder.decode(MyType.self, from: data)
>>> print(decoded)
>>>
>>> print(values == decoded) // => true
>>> On 19 Oct 2017, at 20:15, David Baraff wrote:
>>>
>>> Begin forwarded message:
>>>
>>>> From: Itai Ferber <[email protected] <mailto:[email protected]>>
>>>> Subject: Re: [swift-users] dealing with heterogenous lists/dictionary with
>>>> Codable
>>>> Date: October 19, 2017 at 9:39:25 AM PDT
>>>> To: David Baraff <[email protected] <mailto:[email protected]>>
>>>> Cc: Geordie Jay <[email protected] <mailto:[email protected]>>, swift-users
>>>> <[email protected] <mailto:[email protected]>>
>>>>
>>>> Hi David and Geordie,
>>>>
>>>> That approach won’t work — encoders and decoders only work directly with
>>>> concrete Codable types (e.g. String, Int, MyFoo [where MyFoo is Codable],
>>>> etc.).
>>>> This is by design: since there is no type information stored in the JSON
>>>> payload, there isn’t necessarily a way to tell how to decode the type
>>>> you’re looking at, so asking for a generalCodable` isn’t helpful.
>>>>
>>>> Since it’s unlikely that what you truly need is a [String : Any] but
>>>> really a [String : <one of String, Int, MyFoo, etc.>], one easy way to
>>>> decode this type is to create a wrapper enum or similar which overrides
>>>> init(from:) to be able to decode from one of those types. You can then ask
>>>> to decode a [String : MyWrapperType] and use that instead.
>>>>
>>>> What types are you expecting in the dictionary?
>>>>
>>>>
>>>
>>> The problem is that I want to be able to encode types T where
>>> (a) T is String, Int
>>> (b) lists of T
>>> (c ) dictionaries of type <String, T>
>>>
>>> The problem is the recursive nature: yes, my types are simple (say only
>>> base types String and Int) but the “nesting” level may be quite deep (a
>>> list of list of dictionaries of <etc.).
>>>
>>>
>>> Let’s turn this around: in addition to the JSONEncoder, one can also use
>>> the PropertyListEncoder.
>>>
>>> Are we saying that something one could pull from a property list file
>>> (which is pretty much what i want: arbitrary deep nesting of basic types)
>>> is also not Codable? So a PropertyListEncoder could not encode actual
>>> property lists?
>>>
>>> I really do want a heterogenous container. I think I am stuck.
>>>
>>>> — Itai
>>>>
>>>> On 19 Oct 2017, at 18:11, David Baraff via swift-users wrote:
>>>>
>>>> I’ll try. Is that cast smart enough to apply recursively? We shall see.
>>>>
>>>> Sent from my iPad
>>>>
>>>> On Oct 19, 2017, at 7:34 AM, Geordie Jay <[email protected]
>>>> <mailto:[email protected]>> wrote:
>>>>
>>>>> I mean can you do something along the lines of
>>>>>
>>>>> let codableDict = stringAnyDict as? [String : Codable]
>>>>>
>>>>> ?
>>>>>
>>>>> I’m not at a computer to test it myself
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> David Baraff <[email protected] <mailto:[email protected]>>
>>>>> schrieb am Do. 19. Okt. 2017 um 15:45:
>>>>> That’s exactly what I want. The ironic part is that I got my dictionary
>>>>> by decoding a Json file. If that’s where my dictionary came from, is
>>>>> there a simple way of coercing the Json serialization routines to give me
>>>>> back codables, rather than Anys?
>>>>>
>>>>>
>>>>> Sent from my iPad
>>>>>
>>>>> On Oct 19, 2017, at 3:38 AM, Geordie Jay <[email protected]
>>>>> <mailto:[email protected]>> wrote:
>>>>>
>>>>>>
>>>>>> David Baraff via swift-users <[email protected]
>>>>>> <mailto:[email protected]>> schrieb am Do. 19. Okt. 2017 um 03:47:
>>>>>> So I have simple structs like this:
>>>>>>
>>>>>> struct Library: Codable {
>>>>>> let domain: String
>>>>>> let unit: String
>>>>>> }
>>>>>>
>>>>>> and it’s super-simple to serialize. Yay.
>>>>>>
>>>>>> But:
>>>>>>
>>>>>> struct LibraryGroup : Codable { // I wish...
>>>>>> let libraries: [Library]
>>>>>> let someDict: [String : Any]
>>>>>> }
>>>>>>
>>>>>> I haven’t tried this, but is it possible to have a dictionary of [String
>>>>>> : Codable] ? Because that’s exactly the type requirements you’re
>>>>>> describing, no?
>>>>>>
>>>>>> Geordie
>>>>>>
>>>>>>
>>>>>> So what I’m looking for is something where if the values in someDict are
>>>>>> themselves Codable, I can serialize things, and if they’re not, I can’t.
>>>>>> In my previous scheme, I was using NSKeyedArchiver to serialize
>>>>>> everything, manualy, including someDict; in trying to switch to Codable
>>>>>> I ran smack into the fact that Codable wants to know what all the types
>>>>>> are, in advance.
>>>>>>
>>>>>> Am I just stuck? How do I get the best of both worlds, where the
>>>>>> compiler can make use of the fact that it can see the data types of my
>>>>>> structures, while still being able to serialize heterogenous data like
>>>>>> is found in LibraryGroup?
>>>>>>
>>>>>> Is my only alternative to write a custom coder for LibraryGroup? Is
>>>>>> there any hope I could teach Codable what to do with
>>>>>> [String: Any]
>>>>>>
>>>>>> ?
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> swift-users mailing list
>>>>>> [email protected] <mailto:[email protected]>
>>>>>> https://lists.swift.org/mailman/listinfo/swift-users
>>>>>> <https://lists.swift.org/mailman/listinfo/swift-users>
>>>>
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>>>
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