How do you reference an integer in a list of integers when you render a json object:
rendered = json.loads(f.read() % {
"site_id": site_id,
"immutable_date_start": immutable_date_start,
"immutable_date_end": immutable_date_end,
"event_date_start": event_date_start,
"event_date_end": event_date_start
})
Here, site_id is an integer, but when I reference it in the json:
"space": {
"s": ["{{ site_id }}"]
Which just transcribes it to string. Is there a different way to reference integers? I know they are supported hard coded in but it's not what I am looking for.
Related
I'm modelling some JSON - and using the following lines
data class Metadata(
val id: String,
val creators: Array<CreatorsModel>
)
along with:
data class CreatorsModel (
val role: String,
val name: String
)
However keep seeing the error: Array property in data class error.
Any ideas why this is?
FYI, the JSON looks like:
{
"id": "123",
"creators": [{
"role": "Author",
"name": "Marie"
}
]
}
In Kotlin you should aim to use List instead of Array where possible. Array has some JVM implications, and although the compiler will let you, the IDE may prompt you to override equals and hashcode manually. Using List will make things much simpler.
You can find out more about the difference here: Difference between List and Array types in Kotlin
During my fresh adventures with kotlin-react I hit a hard stop when trying to parse some data from my backend which contains enum values.
Spring-Boot sends the object in JSON form like this:
{
"id": 1,
"username": "Johnny",
"role": "CLIENT"
}
role in this case is the enum value and can have the two values CLIENT and LECTURER. If I were to parse this with a java library or let this be handled by Spring-Boot, role would be parsed to the corresponding enum value.
With kotlin-js' JSON.parse, that wouldn't work and I would have a simple string value in there.
After some testing, I came up with this snippet
val json = """{
"id": 1,
"username": "Johnny",
"role": "CLIENT",
}"""
val member: Member = JSON.parse(json) { key: String, value: Any? ->
if (key == "role") Member.Role.valueOf(value.toString())
else value
}
in which I manually have to define the conversion from the string value to the enum.
Is there something I am missing that would simplify this behaviour?
(I am not referring to using ids for the JSON and the looking those up, etc. I am curious about some method in Kotlin-JS)
I have the assumption there is not because the "original" JSON.parse in JS doesn't do this and Kotlin does not add any additional stuff in there but I still have hope!
As far as I know, no.
The problem
Kotlin.JS produces an incredibly weird type situation when deserializing using the embedded JSON class, which actually is a mirror for JavaScript's JSON class. While I haven't done much JavaScript, its type handling is near non-existent. Only manual throws can enforce it, so JSON.parse doesn't care if it returns a SomeCustomObject or a newly created object with the exact same fields.
As an example of that, if you have two different classes with the same field names (no inheritance), and have a function that accepts a variable, it doesn't care which of those (or a third for that matter) it receives as long as the variables it tries accessing on the class exists.
The type issues manifest themselves into Kotlin. Now wrapping it back to Kotlin, consider this code:
val json = """{
"x": 1, "y": "yes", "z": {
"x": 42, "y": 314159, "z": 444
}
}""".trimIndent()
data class SomeClass(val x: Int, val y: String, val z: Struct)
data class Struct(val x: Int, val y: Int, val z: Int)
fun main(args: Array<String>) {
val someInstance = JSON.parse<SomeClass>(json)
if(someInstance.z::class != Struct::class) {
println("Incompatible types: Required ${Struct::class}, found ${someInstance.z::class}");
}
}
What would you expect this to print? The natural would be to expect a Struct. The type is also explicitly declared
Unfortunately, that is not the case. Instead, it prints:
Incompatible types: Required class Struct, found class Any
The point
The embedded JSON de/serializer isn't good with types. You might be able to fix this by using a different serializing library, but I'll avoid turning this into a "use [this] library".
Essentially, JSON.parse fails to parse objects as expected. If you entirely remove the arguments and try a raw JSON.parse(json); on the JSON in your question, you'll get a role that is a String and not a Role, which you might expect. And with JSON.parse doing no type conversion what so ever, that means you have two options: using a library, or using your approach.
Your approach will unfortunately get complicated if you have nested objects, but with the types being changed, the only option you appear to have left is explicitly parsing the objects manually.
TL;DR: your approach is fine.
I'm new to Go and working hard to follow its style and I'm not sure how to proceed.
I want to push a JSON object to a Geckoboard leaderboard, which I believe requires the following format based on the API doc and the one for leaderboards specifically:
{
"api_key": "222f66ab58130a8ece8ccd7be57f12e2",
"data": {
"item": [
{ "label": "Bob", "value": 4, "previous_value": 6 },
{ "label": "Alice", "value": 3, "previous_value": 4 }
]
}
}
My instinct is to build a struct for the API call itself and another called Contestants, which will be nested under item. In order to use json.Marshall(Contestant1), the naming convention of my variables would not meet fmt's expectations:
// Contestant structure to nest into the API call
type Contestant struct {
label string
value int8
previous_rank int8
}
This feels incorrect. How should I configure my Contestant objects and be able to marshall them into JSON without breaking convention?
To output a proper JSON object from a structure, you have to export the fields of this structure. To do it, just capitalize the first letter of the field.
Then you can add some kind of annotations, to tell your program how to name your JSON fields :
type Contestant struct {
Label string `json:"label"`
Value int8 `json:"value"`
PreviousRank int8 `json:"previous_rank"`
}
I'm using Scala & Argonaut, trying to parse the following JSON:
[
{
"name": "apple",
"type": "fruit",
"size": 3
},
{
"name": "jam",
"type": "condiment",
"size": 5
},
{
"name": "beef",
"type": "meat",
"size": 1
}
]
And struggling to work out how to iterate and extract the values into a List[MyType] where MyType will have name, type and size properties.
I will post more specific code soon (i have tried many things), but basically I'm looking to understand how the cursor works, and how to iterate through arrays etc. I have tried using \\ (downArray) to move to the head of the array, then :->- to iterate through the array, then --\ (downField) is not available (at least IntelliJ doesn't think so).
So the question is how do i:
navigate to the array
iterate through the array (and know when I'm done)
extract string, integer etc. values for each field - jdecode[String]? as[String]?
The easiest way to do this is to define a codec for MyType. The compiler will then happily construct a decoder for List[MyType], etc. I'll use a plain class here (not a case class) to make it clear what's happening:
class MyType(val name: String, val tpe: String, val size: Int)
import argonaut._, Argonaut._
implicit def MyTypeCodec: CodecJson[MyType] = codec3(
(name: String, tpe: String, size: Int) => new MyType(name, tpe, size),
(myType: MyType) => (myType.name, myType.tpe, myType.size)
)("name", "type", "size")
codec3 takes two parameter lists. The first has two parameters, which allow you to tell how to create an instance of MyType from a Tuple3 and vice versa. The second parameter list lets you specify the names of the fields.
Now you can just write something like the following (if json is your string):
Parse.decodeValidation[List[MyType]](json)
And you're done.
Since you don't need to encode and are only looking at decoding, you can do as suggested by Travis, but by implementing another implicit: MyTypeDecodeJson
implicit def MyTypeDecodeJson: DecodeJson[MyType] = DecodeJson(
raw => for {
name <- raw.get[String]("name")
type <- raw.get[String]("type")
size <- raw.get[Int]("size")
} yield MyType(name, type, size))
Then to parse your list:
Parse.decodeValidation[List[MyType]](jsonString)
Assuming MyType is a case class, the following works too:
case class MyType(name: String, type: String, size: Int)
object MyType {
implicit val createCodecJson: CodecJson[MyType] = CodecJson.casecodec3(apply, unapply)(
"name",
"type",
"size"
)
}
I'm looking to create what I feel is probably a basic JSON object, but my limited knowledge of JSON is making it difficult.
I am trying to create an object that will ultimately be passed to a .NET AMSX web service. The parameter for the web service is a P1Request object, which is defined as follows:
Public Class P1RequestClause
Public Property FieldId() As Integer
Public Property OperatorId() As Integer
Public Property Value() As String
End Class
Public Class P1Request
Public Property Fields() As String()
Public Property Clauses() As P1RequestClause()
End Class
On the client side, I have a number of different form fields, the values of which I would like to wrap up in a JSON object to pass.
I am unsure of what structure my JSON object needs to match the .NET class.
Ideally my data, in psudocode, would look like:
P1Request:
Fields:
Field1,
Field2,
Field3
Clauses:
P1RequestClause:
Id1,
OpId1,
SomeValue
P1RequestClause:
Id2,
Opid2,
AnotherValue
What would this look like in JSON? It's the array of Fields in P1Request is the part that confuses me the most. As I understand JSON, it's all name:value pairs, and making an array of a single field is throwing me.
{
"Fields": [
"moo",
"says",
"the cow"
],
"Clauses": [
{
"FieldId": 1,
"OperatorId": 3,
"Value": "foo"
},
{
"FieldId": 2,
"OperatorId": 0,
"Value": "bar"
}
]
}
JSON consists of primitive types (numbers, strings, null...), objects (which are key-value pair collections), and arrays, which is what you were missing.