I have this const variable in flutter:
static const questions = [
{
"question": "question",
"answers": ["1", "2"],
"message":
"message",
},
]
how to access to "1" from dart??
I try using QuestionContent.questions[0]["answers"][0].
But I got error "The method '[]' can't be unconditionally invoked because the receiver can be 'null'"
Try use:
Text((QuestionContent.questions[0] as Map<String, dynamic>)['answers'][0] ?? '')
or:
Text((questions[0]['answers'] as List<String>)[0]),
Try code below:
const questions = [
{
"question": "question",
"answers": ["1", "2"],
"message":
"message",
},
];
Map<String, Object> question = questions[0];
List<String> answers = question["answers"] as List<String>;
String firstAnswer = answers.elementAt(0);
The reason you get the error is the compiler could not tell whether your QuestionContent.questions[0]["answers"] is null or not:
Related
I have the following terraform config:
resource "aws_dynamodb_table_item" "my_table" {
table_name = aws_dynamodb_table.my_table.name
hash_key = aws_dynamodb_table.my_table.hash_key
item = <<ITEM
{
"id": {"S": "nameAndCodes"},
"data": {"S": "[
{
"code": "03",
"displayName": "name1"
},
{
"code": "04",
"displayName": "name2"
}
]"}
}
ITEM
}
When the plan stage executes I receive the error:
Error: Invalid format of "item": Decoding failed: invalid character '\r' in string literal
The only way i can get this to work is to make the whole json a single line as follows:
"data": {"S": "[{\"code\": \"03\", \"displayName\": \"name1\"},{\"code\": \"04\", \"displayName\": \"name2\"}]"
This looks very ugly and difficult to manage.
Does anyone know how I can enter a multiline JSON inside a <<ITEM block?
To resolve that issue, You can use the jsonencode function to set the item value and put entire JSON object in there. Here is an example in Terraform from my project which creates a DynamoDB table and put an initial item.
resource "aws_dynamodb_table" "customer_table" {
name = "customer"
billing_mode = "PAY_PER_REQUEST"
hash_key = "customerId"
stream_enabled = false
attribute {
name = "customerId"
type = "S"
}
}
resource "aws_dynamodb_table_item" "customer_table_item" {
table_name = aws_dynamodb_table.customer_table.name
hash_key = aws_dynamodb_table.customer_table.hash_key
depends_on = [aws_dynamodb_table.customer_table]
item = jsonencode({
"customerId" : {
"S" : "1"
},
"firstName" : {
"S" : "John"
},
"lastName" : {
"S" : "Doe"
},
})
}
commands:
terrform init
terraform fmt
terraform plan
terraform apply
First of all, I'm very new to JSON concept so sorry if my question is silly or very simple to answer.
I want to use Oxford Dictionary API for simple app which I'm writing in Kotlin, here is the response from API as JSON:
{
"metadata": {
"provider": "Oxford University Press"
},
"results": [
{
"id": "hello",
"language": "en",
"lexicalEntries": [
{
"entries": [
{
"etymologies": [
"early 19th century: variant of earlier hollo; related to holla"
],
"homographNumber": "000",
"senses": [
{
"definitions": [
"used as a greeting or to begin a telephone conversation"
],
"examples": [
{
"text": "hello there, Katie!"
}
],
"id": "m_en_gbus0460730.012",
"short_definitions": [
"used as greeting"
],
"subsenses": [
{
"definitions": [
"used to express surprise"
],
"examples": [
{
"text": "hello, what's all this then?"
}
],
"id": "m_en_gbus0460730.017",
"regions": [
"British"
],
"short_definitions": [
"used to express surprise"
]
},
{
"definitions": [
"used as a cry to attract someone's attention"
],
"examples": [
{
"text": "‘Hello below!’ he cried"
}
],
"id": "m_en_gbus0460730.018",
"short_definitions": [
"used attract attention"
]
},
{
"definitions": [
"used informally to express sarcasm or anger"
],
"examples": [
{
"text": "Hello! Did you even get what the play was about?"
}
],
"id": "m_en_gbus0460730.019",
"short_definitions": [
"used informally to express sarcasm or anger"
]
}
]
And now, I would like to extract only "definitions" from this JSON object but as you can see it is nested within other JSON arrays, my code so far looks like this:
var resultJSON = JSONObject(result)
var JSON_results = resultJSON.getJSONArray("results")
var JSON_lexical = JSON_results.getJSONObject(0).getJSONArray("lexicalEntries")
var JSON_entries = JSON_lexical.getJSONObject(0).getJSONArray("entries")
var JSON_senses = JSON_entries.getJSONObject(0).getJSONArray("senses")
var JSON_definitions = JSON_senses.getJSONObject(0).getJSONArray("definitions")
Log.i("JSON", JSON_definitions.getString(0))
I know that there needs to be a better way of doing this but I can't find how.
Kotlin actually makes it easier to map such responses with something called "data classes". So you can simply paste the JSON response in an online JSON to Kotlin Data Class Generator e.g. https://json2kotlin.com
It churns out .kt files like this:
data class Json4Kotlin_Base (
val metadata : Metadata,
val results : List<Results>
)
and thn you can simply pass on the response JSON to the Data class mapping like this:
val json = getJson() // your json value here
val topic = Gson().fromJson(json, Json4Kotlin_Base::class.java)
In case you're looking for GSON annotations in the generated models, chose the option when you generate those.
Here's a video tutorial for step by step process about it.
https://www.youtube.com/watch?v=n46WbgNoEnE
Try as follow
val justDefinitions = mutableListOf<String>()
JSON_senses.forEach {
val definitions = it.getJSONArray("definitions")
for (i in 0 until definitions.length()) { {
justDefinitions.add(it.getString(i))
}
}
I get an error when I try to save an array that comes from a JSON string. I've tried to use RLMArray with no success.
The error I receive is:
'RLMException', reason: 'Property 'page' is of type 'RLMArray<(null)>' which is not a supported RLMArray object type.
My model class:
public class Project: Object, Mappable {
dynamic var id = 0
dynamic var user: User!
dynamic var page: RLMArray!
dynamic var error_message: String! = ""
dynamic var status: String! = ""
override public static func primaryKey() -> String? {
return "id"
}
required convenience public init?(_ map: Map) {
self.init()
mapping(map)
}
public func mapping(map: Map) {
user <- map["user"]
page <- map["page"]
error_message <- map["error_message"]
status <- map["status"]
}
}
JSON File:
let parameters = [
"user": [
"username": "Marcus",
"password": "123asd"
],
"page": [
"home": [
[
"kind": "navigation",
"title": "suite",
"image": "ic_suite",
"backgroundImage": "ic_background1"
],
[
"kind": "navigation",
"title": "jardim",
"image": "ic_jardim",
"backgroundImage": "ic_background2"
]
],
"suite": [
[
"kind": "button",
"title": "My Master Suite",
"textColor": "0x000000",
"textSize": "16"
]
]
],
"status": "success",
"error_message": ""
]
self.project = Mapper<Project>().map(parameters)
Your class inherits from Object, Realm Swift's base class, but is attempting to use RLMArray, a Realm Objective-C type, in its interface. You cannot mix Realm Swift and Realm Objective-C in this manner. You should use List<T> for array properties when using Realm Swift.
I have this two tables from the diagrams.For every question i can have multiple answer.
I want to get data by question id in json format like this:
var initialData = [
{question_id: "1", Description: "Danny", Status: "1", answers: [
{ answer_id: "1", description: "AAAAA" },
{ answer_id: "2", description: "Bbbbb" }]
}
];
I use this code
var question = db.Questions.FirstOrDefault((p) => p.questionID== id);
return this.Json(question , JsonRequestBehavior.AllowGet);
and i get this
var initialData = [
{question_id: "1", Description: "Danny", Status: "1", answers:null
}
];
Can you help my please with a solution.
Can you try this please.
var question = db.Questions.Include("Answer").FirstOrDefault((p) => p.questionID== id);
Have a look at the ado.Net blog
I'd like to deserialize this using GSON into a list of Post, but can't figure out how to tell GSON how to ignore the root element "posts" (as its an object) and just process the array.
I've got:
Type postTypeList = new TypeToken<List<Post>>(){}.getType();
JsonParser jsonParser = new JsonParser();
JsonElement jsonElement = jsonParser.parse(myJSONString);
JsonObject postsRootObj = jsonElement.getAsJsonObject();
List<Post> postList = gson.fromJson(postsRootObj.get("posts"), postTypeList);
BUT.. I'd rather not have the whole JsonParser, I'd rather just pass it directly into the gson.fromJson function.. Is there a way to do this?
{ "posts":
[
{
"username": "John",
"message": "I'm back",
"time": "2010-5-6 7:00:34"
"validator":[{
"prog": "Name1",
"name": "Name2",
"computername": "Name3",
"date": "2010-11-20 19:39:55"
}]
}
,
{
"username": "Smith",
"message": "I've been waiting",
"time": "2010-4-6 10:30:26"
"validator":[{
"prog": "Name1",
"name": "Name2",
"computername": "Name3",
"date": "2010-11-20 19:39:55"
}]
}
]}
Create a wrapper class which will have List<Post> as its member
public class PostList{
private List<Post> posts;
// getter and setters for posts
}
And then use fromJson in the similar fashion
List<Post> postList = gson.fromJson(myJSONString,PostList.class);
There is a correction from above. Usage should be :
PostList postList = gson.fromJson(myJSONString,PostList.class);
Post post = postlist.get(index) //index is the index of list you want to access