I post a request to get some json data and try to convert the data to Model
var newDrugs = Array<DxyDrugInfo>()
newDrugs = self.parseDrugJsonToModels(data) ?? []
private func parseDrugJsonToModels(data: NSData) -> Array<DxyDrugInfo>?{
let json = JSON(data: data)
if let drugsArray = json["data"].arrayObject as? Array<[String : AnyObject]>, success = json["success"].bool where success {
var sortedArray = Array<DxyDrugInfo>()
for drugDic in drugsArray {
let drugInfo = DxyDrugInfo()
drugInfo.setValuesForKeysWithDictionary(drugDic)
sortedArray.append(drugInfo)
}
return sortedArray
}
return nil
}
DxyDrugInfo is a Objective-C Model Class
My question is the sortedArray's type is Array of DxyDrugInfo, and it changed to
when assigned to newDrugs.
I want to convert it to DxyDrugInfo and I also want to what the type is.
Thank you
That type you're looking at, #lvalue [DxyDrugInfo], is "array of DxyDrugInfo". You're already done! The square brackets around a type are shorthand for "array", that is:
[DxyDrugInfo] == Array<DxyDrugInfo>
and #lvalue just means that newDrugs is a variable you can assign to. (It's the opposite of "r-value", which is a value you could assign to an "l-value".)
Related
I have some code which looks like this, where param is of a data class type:
val options = if (param.language == null) {
param.copy(language = default())
} else {
param
}
Now, however, the language object has been moved into a hierarchy of nullable objects, so the check must look like this:
if (param.subObj?.nextObj?.language == null) { ... }
How do I use the copy idiom in this case?
One way to do this is:
val newParam = when {
param.subObj == null -> param.copy(subObj = SubObj(nextObj = NextObj(language = Language())))
param.subObj.nextObj == null -> param.copy(subObj = param.subObj.copy(nextObj = NextObj(language = Language())))
param.subObj.nextObj.language == null -> param.copy(subObj = param.subObj.copy(nextObj = param.subObj.nextObj.copy(language = Language())))
else -> param
}
I agree that this doesn't look very clean but this seems to be the only way to me, because at each step you need to check if the current property is null or not. If it is null, you need to use the default instance otherwise you need to make a copy.
Could you do something like this?
// you could create a DefaultCopyable interface if you like
data class SubObj(val prop1: Double? = null, val nextObj: NextObj? = null) {
fun copyWithDefaults() =
copy(prop1 = prop1 ?: 1.0, nextObj = nextObj?.copyWithDefaults() ?: NextObj())
}
data class NextObj(val name: String? = null) {
fun copyWithDefaults() = copy(name = name ?: "Hi")
}
I think you need a special function because you're not using the standard copy functionality exactly, you need some custom logic to define defaults for each class. But by putting that function in each of your classes, they all know how to copy themselves, and each copy function that works with other types can just call their default-copy functions.
The problem there though is:
fun main() {
val thing = SubObj(3.0)
val newThing = thing.copyWithDefaults()
println("$thing\n$newThing")
}
> SubObj(prop1=3.0, nextObj=null)
> SubObj(prop1=3.0, nextObj=NextObj(name=null))
Because nextObj was null in SubObj, it has to create one instead of copying it. But the real default value for name is null - it doesn't know how to instantiate one with the other defaults, that's an internal detail of NextObj. You could always call NextObj().copyWithDefaults() but that starts to look like a code smell to me - why isn't the default value for the parameter the actual default value you want? (There are probably good reasons, but it might mean there's a better way to architect what you're up to)
Following a question where the answer provided a working solution to serialize / deserialize discriminated unions (IgnoreMissingMember setting doesn't seem to work with FSharpLu.Json deserializer)
I have now a practical case where this fails (although it works in simpler cases).
here is the test code:
open System.Collections.Generic
open Microsoft.FSharpLu.Json
open Newtonsoft.Json
open Newtonsoft.Json.Serialization
// set up the serialization / deserialization based on answer from:
// https://stackoverflow.com/questions/62364229/ignoremissingmember-setting-doesnt-seem-to-work-with-fsharplu-json-deserializer/62364913#62364913
let settings =
JsonSerializerSettings(
NullValueHandling = NullValueHandling.Ignore,
Converters = [| CompactUnionJsonConverter(true, true) |]
)
let serialize object =
JsonConvert.SerializeObject(object, settings)
let deserialize<'a> object =
JsonConvert.DeserializeObject<'a>(object, settings)
// define the type used
type BookSide =
| Bid
| Ask
type BookEntry =
{
S : float
P : float
}
type BookSideData =
Dictionary<int, BookEntry>
type BookData =
{
Data: Dictionary<BookSide, BookSideData>
}
static member empty =
{
Data = Dictionary<BookSide, BookSideData>(dict [ (BookSide.Bid, BookSideData()); (BookSide.Ask, BookSideData()) ])
}
// make some sample data
let bookEntry = { S=3.; P=5. }
let bookData = BookData.empty
bookData.Data.[BookSide.Bid].Add(1, bookEntry)
// serialize. This part works
let s = serialize bookData
// deserialize. This part fails
deserialize<BookData> s
the serialized test data will look like this:
{"Data":{"Bid":{"1":{"S":3.0,"P":5.0}},"Ask":{}}}
but deserializing will crash like this:
Could not convert string 'Bid' to dictionary key type 'FSI_0023+BookSide'. Create a TypeConverter to convert from the string to the key type object.
although the serialization / deserialization of the DU through FSharpLu which has a DU converter.
The reason I am trying to find some automated solution, vs writing a custom TypeConverter (besides the fact I've never done it) is that I have a lot of types I do not control to go through.
Here is a fiddle:
https://dotnetfiddle.net/Sx0k4x
Your basic problem is that you are using BookSide as a dictionary key -- but this is an f# union which makes it a complex key -- one not immediately convertible to and from a string. Unfortunately Json.NET does not support complex dictionary keys out of the box as is stated in its Serialization Guide:
When serializing a dictionary, the keys of the dictionary are converted to strings and used as the JSON object property names. The string written for a key can be customized by either overriding ToString() for the key type or by implementing a TypeConverter. A TypeConverter will also support converting a custom string back again when deserializing a dictionary.
There are two basic approaches to handling this issue:
Implement a TypeConverter as is shown in, e.g., Not ableTo Serialize Dictionary with Complex key using Json.net.
Serialize the dictionary as an array of key/value pair objects e.g. as is shown in Serialize dictionary as array (of key value pairs).
Since your data model includes dictionaries with a variety of keys (DU, strings and ints) the second solution would appear to be the only possibility. The following DictionaryConverter should have the necessary logic:
let inline isNull (x:^T when ^T : not struct) = obj.ReferenceEquals (x, null)
type Type with
member t.BaseTypesAndSelf() =
t |> Seq.unfold (fun state -> if isNull state then None else Some(state, state.BaseType))
member t.DictionaryKeyValueTypes() =
t.BaseTypesAndSelf()
|> Seq.filter (fun i -> i.IsGenericType && i.GetGenericTypeDefinition() = typedefof<Dictionary<_,_>>)
|> Seq.map (fun i -> i.GetGenericArguments())
type JsonReader with
member r.ReadAndAssert() =
if not (r.Read()) then raise (JsonReaderException("Unexpected end of JSON stream."))
r
member r.MoveToContentAndAssert() =
if r.TokenType = JsonToken.None then r.ReadAndAssert() |> ignore
while r.TokenType = JsonToken.Comment do r.ReadAndAssert() |> ignore
r
type internal DictionaryReadOnlySurrogate<'TKey, 'TValue>(i : IDictionary<'TKey, 'TValue>) =
interface IReadOnlyDictionary<'TKey, 'TValue> with
member this.ContainsKey(key) = i.ContainsKey(key)
member this.TryGetValue(key, value) = i.TryGetValue(key, &value)
member this.Item with get(index) = i.[index]
member this.Keys = i.Keys :> IEnumerable<'TKey>
member this.Values = i.Values :> IEnumerable<'TValue>
member this.Count = i.Count
member this.GetEnumerator() = i.GetEnumerator()
member this.GetEnumerator() = i.GetEnumerator() :> IEnumerator
type DictionaryConverter () =
// ReadJson adapted from this answer https://stackoverflow.com/a/28633769/3744182
// To https://stackoverflow.com/questions/28451990/newtonsoft-json-deserialize-dictionary-as-key-value-list-from-datacontractjsonse
// By https://stackoverflow.com/users/3744182/dbc
inherit JsonConverter()
override this.CanConvert(t) = (t.DictionaryKeyValueTypes().Count() = 1) // If ever implemented for IReadOnlyDictionary<'TKey, 'TValue> then reject DictionaryReadOnlySurrogate<'TKey, 'TValue>
member private this.ReadJsonGeneric<'TKey, 'TValue> (reader : JsonReader, t : Type, existingValue : obj, serializer : JsonSerializer) : obj =
let contract = serializer.ContractResolver.ResolveContract(t)
let dict = if (existingValue :? IDictionary<'TKey, 'TValue>) then existingValue :?> IDictionary<'TKey, 'TValue> else contract.DefaultCreator.Invoke() :?> IDictionary<'TKey, 'TValue>
match reader.MoveToContentAndAssert().TokenType with
| JsonToken.StartArray ->
let l = serializer.Deserialize<List<KeyValuePair<'TKey, 'TValue>>>(reader)
for p in l do dict.Add(p)
dict :> obj
| JsonToken.StartObject ->
serializer.Populate(reader, dict)
dict :> obj
| JsonToken.Null -> null // Or throw an exception if you prefer
| _ -> raise (JsonSerializationException(String.Format("Unexpected token {0}", reader.TokenType)))
override this.ReadJson(reader, t, existingValue, serializer) =
let keyValueTypes = t.DictionaryKeyValueTypes().Single(); // Throws an exception if not exactly one.
let m = typeof<DictionaryConverter>.GetMethod("ReadJsonGeneric", BindingFlags.NonPublic ||| BindingFlags.Instance ||| BindingFlags.Public);
m.MakeGenericMethod(keyValueTypes).Invoke(this, [| reader; t; existingValue; serializer |])
member private this.WriteJsonGeneric<'TKey, 'TValue> (writer : JsonWriter, value : obj, serializer : JsonSerializer) =
let dict = value :?> IDictionary<'TKey, 'TValue>
let keyContract = serializer.ContractResolver.ResolveContract(typeof<'Key>)
// Wrap the value in an enumerator or read-only surrogate to prevent infinite recursion.
match keyContract with
| :? JsonPrimitiveContract -> serializer.Serialize(writer, new DictionaryReadOnlySurrogate<'TKey, 'TValue>(dict))
| _ -> serializer.Serialize(writer, seq { yield! dict })
()
override this.WriteJson(writer, value, serializer) =
let keyValueTypes = value.GetType().DictionaryKeyValueTypes().Single(); // Throws an exception if not exactly one.
let m = typeof<DictionaryConverter>.GetMethod("WriteJsonGeneric", BindingFlags.NonPublic ||| BindingFlags.Instance ||| BindingFlags.Public);
m.MakeGenericMethod(keyValueTypes).Invoke(this, [| writer; value; serializer |])
()
Which you would add to settings as follows:
let settings =
JsonSerializerSettings(
NullValueHandling = NullValueHandling.Ignore,
Converters = [| CompactUnionJsonConverter(true, true); DictionaryConverter() |]
)
And generates the following JSON for your bookData:
{
"Data": [
{
"Key": "Bid",
"Value": [
{
"Key": 1,
"Value": {
"S": 3.0,
"P": 5.0
}
}
]
},
{
"Key": "Ask",
"Value": []
}
]
}
Notes:
The converter works for all Dictionary<TKey, TValue> types (and subtypes).
The converter detects whether the dictionary keys will be serialized using a primitive contract, and if so, serializes the dictionary compactly as a JSON object. If not the dictionary is serialized as an array. You can observe this in the JSON shown above: the Dictionary<BookSide, BookSideData> dictionary is serialized as a JSON array, and the Dictionary<int, BookEntry> dictionary is serialized as a JSON object.
During deserialization the converter detects whether the incoming JSON value is an array or object, and adapts as required.
The converter is only implemented for the mutable .Net Dictionary<TKey, TValue> type. The logic would require some slight modification to deserialize the immutable Map<'Key,'Value> type.
Demo fiddle here.
I'm getting the following JSON response from the server:
{
"userId":"123456789",
"displayName":"display name"
}
When I use NSJSONSerialization.JSONObjectWithData and then prints the result NSDictionary I see in the console the following:
userId = 123456789
displayName = "display name"
Why do JSONObjectWithData changes the userId field type from String to a number?
It doesn't. The JSON deserialisation respects the data type and will maintain it. You can't tell the data type from a simple description log, you need to actually interrogate the class. The description log will quote some things if it makes more sense for the human reader, like spaces in the description, but it also omits quotes in some cases.
It doesn't.
Don't infer a variable type from its log representation, just test. Fire a Playground with this, for example:
let str = "{\"userId\":\"123456789\",\"displayName\":\"display name\"}"
if let data = str.dataUsingEncoding(NSUTF8StringEncoding),
jsonResult = try? NSJSONSerialization.JSONObjectWithData(data, options: []),
jsonObject = jsonResult as? [String:String],
id = jsonObject["userId"] {
print("User ID is " + id)
}
Is there an actionscript library providing a queuing system?
This system would have to allow me to pass the object, the function I want to invoke on it and the arguments, something like:
Queue.push(Object, function_to_invoke, array_of_arguments)
Alternatively, is it possible to (de-)serialize a function call? How would I evaluate the 'function_to_invoke' with the given arguments?
Thanks in advance for your help.
There's no specific queue or stack type data structure available in ActionScript 3.0 but you may be able to find a library (CasaLib perhaps) that provides something along those lines.
The following snippet should work for you but you should be aware that since it references the function name by string, you won't get any helpful compiler errors if the reference is incorrect.
The example makes use of the rest parameter which allows you to specify an array of arbitrary length as the arguments for your method.
function test(... args):void
{
trace(args);
}
var queue:Array = [];
queue.push({target: this, func: "test", args: [1, 2, "hello world"] });
queue.push({target: this, func: "test", args: ["apple", "pear", "hello world"] });
for (var i:int = 0; i < queue.length; i ++)
{
var queued:Object = queue[i];
queued.target[queued.func].apply(null, queued.args);
}
Sure, that works similar to JavaScript
const name:String = 'addChild'
, container:Sprite = new Sprite()
, method:Function = container.hasOwnProperty(name) ? container[name] : null
, child:Sprite = new Sprite();
if (method)
method.apply(this, [child]);
So a query method could look like:
function queryFor(name:String, scope:*, args:Array = null):void
{
const method:Function = scope && name && scope.hasOwnProperty(name) ? scope[name] : null
if (method)
method.apply(this, args);
}
I know how to serialize in F# using mutable objects, but is there a way to serialize/deserialize using record types using either XmlSerializer or the DataContractSerializer? looks like there is a way to do this for a discriminated union using the KnownType attribute, but i am looking for a way to use non-mutable records without default constructor...
Beginning with F# 3.0, serialization of record types is now supported by applying the CliMutableAttribute to the type. Example:
[<CLIMutable>]
type MyRecord = { Name : string; Age : int }
This example is taken from http://blogs.msdn.com/b/fsharpteam/archive/2012/07/19/more-about-fsharp-3.0-language-features.aspx, which includes a discussion of this feature and three other new features in F# 3.0: triple-quoted strings, automatic properties, and unused variable warnings.
The sample code for reading data from Freebase by Jomo Fisher uses DataContractJsonSerializer to load data into immutable F# records. The declaration of the record that he uses looks like this:
[<DataContract>]
type Result<'TResult> = { // '
[<field: DataMember(Name="code") >]
Code:string
[<field: DataMember(Name="result") >]
Result:'TResult // '
[<field: DataMember(Name="message") >]
Message:string }
The key point here is that the the DataMember attribute is attached to the underlying field that's actually used to store the data and not to the read-only property that the F# compiler generates (using the field: modifier on the attribute).
I'm not 100% sure if this is going to work with other types of serialization (probably not), but it may be a useful pointer to start with...
EDIT I'm not sure if I'm missing something here, but the following basic example works fine for me:
module Demo
#r "System.Runtime.Serialization.dll"
open System.IO
open System.Text
open System.Xml
open System.Runtime.Serialization
type Test =
{ Result : string[]
Title : string }
do
let sb = new StringBuilder()
let value = { Result = [| "Hello"; "World" |]; Title = "Hacking" }
let xmlSerializer = DataContractSerializer(typeof<Test>);
xmlSerializer.WriteObject(new XmlTextWriter(new StringWriter(sb)), value)
let sr = sb.ToString()
printfn "%A" sr
let xmlSerializer = DataContractSerializer(typeof<Test>);
let reader = new XmlTextReader(new StringReader(sr))
let obj = xmlSerializer.ReadObject(reader) :?> Test
printfn "Reading: %A" obj
EDIT 2 If you want to generate cleaner XML then you can add attributes like this:
[<XmlRoot("test")>]
type Test =
{ [<XmlArrayAttribute("results")>]
[<XmlArrayItem(typeof<string>, ElementName = "string")>]
Result : string[]
[<XmlArrayAttribute("title")>]
Title : string }
It doesn't use XmlSerializer or the DataContractSerializer, but Json.NET 6.0 includes nice F# support.
It looks like this:
type TestTarget =
{ a: string
b: int }
[<TestFixture>]
type JsonTests() =
[<Test>]
member x.``can serialize``() =
let objectUnderTest = { TestTarget.a = "isa"; b = 9 }
let jsonResult: string = Newtonsoft.Json.JsonConvert.SerializeObject(objectUnderTest)
printfn "json is:\n%s" jsonResult
let xmlResult = Newtonsoft.Json.JsonConvert.DeserializeXmlNode(jsonResult, "root")
printfn "xml is:\n%s" (xmlResult.OuterXml)
let jsonRoundtrip = Newtonsoft.Json.JsonConvert.DeserializeObject<TestTarget>(jsonResult)
printfn "json roundtrip: %A" jsonRoundtrip
let xmlAsJson = Newtonsoft.Json.JsonConvert.SerializeXmlNode(xmlResult, Newtonsoft.Json.Formatting.Indented, true)
printfn "object -> json -> xml -> json:\n%A" xmlAsJson
let xmlRoundtrip = Newtonsoft.Json.JsonConvert.DeserializeObject<TestTarget>(xmlAsJson)
printfn "xml roundtrip:\n%A" xmlRoundtrip
Assert.That(true, Is.False)
()
json is:
{"a":"isa","b":9}
xml is:
<root><a>isa</a><b>9</b></root>
json roundtrip: {a = "isa";
b = 9;}
object -> json -> xml -> json:
"{
"a": "isa",
"b": "9"
}"
xml roundtrip:
{a = "isa";
b = 9;}
You can use this series of annotations on the properties of classes to format the XML:
[XmlRoot("root")]
[XmlElement("some-element")]
[XmlAttribute("some-attribute")]
[XmlArrayAttribute("collections")]
[XmlArrayItem(typeof(SomeClass), ElementName = "item")]
I use the attributes on my c# classes, but deserialize in F# (c# classes are ina referenced lib).
in f#:
use file = new FileStream(filePath, FileMode.Open)
let serializer= XmlSerializer(typeof<SomeClass>)
let docs = serializer.Deserialize file :?> SomeClass