how to update JSON value. I am using flutter with a REST API to change the data but I'm struggling how to refresh my JSON data sorry friends I don't know much about the flutter so please help me out about it please find JSON'S Object below:
{
id: 1,
clef: "Y8F5eEo0",
IndiceSensibilite: "0.04",
Objectif: "1.00"
}
I want to update the value of IndiceSensibilite using a textField.
I m here for more clarification.
i will be very thankful if there's someone who gonna help me.
You can transform the JSON into an Object, make your modifications and back to JSON:
import 'dart:convert'; // make sure you imported this library
String jsonValue = '{"id": 1, "clef": "Y8F5eEo0", "indiceSensibilite": "0.04", "objectif": "1.00" }'; // original JSON
Use a Future to convert it into Object:
Future<ToObject> jsonToObject() async {
var parse = json.decode(jsonValue);
return ToObject.parseJson(parse);
}
and your Object (ToObject in my case) will have the following model and methods:
class ToObject {
int id;
String clef;
String indiceSensibilite;
String objectif;
ToObject({this.id, this.clef, this.indiceSensibilite, this.objectif});
factory ToObject.parseJson(Map<String, dynamic> json) => ToObject(
id: json['id'], clef: json['clef'], indiceSensibilite: json['indiceSensibilite'], objectif: json['objectif']);
Map<String, dynamic> toJson() =>
{'id': id, 'clef': clef, 'indiceSensibilite': indiceSensibilite, 'objectif': objectif};
}
I used a FutureBuilder to get the data, modify the value and back to JSON:
FutureBuilder<ToObject>(
future: jsonToObject(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
var object = snapshot.data;
object.indiceSensibilite = "43.00";
return Text(json.encode(object.toJson()));
} else {
return Text("Loading...");
}
},
)
Your end result is a modified JSON to use as you wish:
Related
I'm new in flutter and I have issue with parsing JSON on HTTP response.
I'm using Airtable backend, to store information about posts. These always contain images, and sometimes attachments - PDFs.
I built PODO, like this:
class Post {
String recordid;
String timecreated;
String title;
String content;
String imgurl;
List<Pdf>? pdf;
Post({
required this.recordid,
required this.timecreated,
required this.title,
required this.content,
required this.imgurl,
required this.pdf
});
factory Post.fromJson(Map<String, dynamic> json) {
return Post(
// fields: Fields.fromJson(json['fields']),
recordid: json['id'] as String,
timecreated: json['createdTime'] as String,
title: json['fields']['field1'] as String,
content: json['fields']['field2'] as String,
imgurl: json['fields']['IMG'][0]['url'] as String,
pdf: json['fields']['PDF'] == null ? null : List<Map<String, dynamic>>.from(json['fields']['PDF']).map((dynamic value) => Pdf.fromJson(value)).toList()
);
}
Map<String, dynamic> toJson() => {
"recordid": recordid,
"timecreated": timecreated,
"title": title,
"content": content,
"imgurl": imgurl,
"pdf": pdf
// "fields": List<dynamic>.from(fields.map((x) => x.toJson())),
};
}
class Pdf {
Pdf({
required this.url,
required this.filename
});
Pdf.fromJson(Map<String, dynamic> json) :
url = json['url'],
filename = json['filename'];
final String? url;
final String? filename;
}
I'm not getting any errors, but when I'm trying to use PDF URL in UI, eg. in Text:
ListTile(title: Text(post.pdf.url)),
I'm getting error:
The property 'url' can't be unconditionally accessed because the
receiver can be 'null'.
I'm aiming to create a button on a page, that is clickable when PDF URL exists. When it exists, button navigates to PDF view that use PDF URL to get and display PDF.
Any ideas?
The pdf attribute is nullable, hence it cannot be accessed unconditionally. This is assuming you somehow have the pdf not as a list, otherwise you would need to index your list, your code is incomplete. You could try to do something like this:
if (post.pdf != null) {
//wrap it with a button or whatever
return ListTile(title: Text(post.pdf!.url));
}
else {
return Text('no pdf');
}
Well, sth seems to work, but still cannot parse pdf URL.
I'm getting Text "sth is there" when post.pdf != null and it works, but when I'm changing to get value from model using post.pdf!.url I'm getting same error:
Try correcting the name to the name of an existing getter, or defining
a getter or field named 'url'.
child:Text(post.pdf!.url));
Here's piece of code:
LayoutBuilder(builder: (context, constraints) {
if(post.pdf != null){
return ElevatedButton(onPressed: () => Navigator.of(context).push(
MaterialPageRoute(builder: (context) => PDFview(pdf: [])
)),
child:Text(post.pdf!.url));
}else{
return ElevatedButton(onPressed: null,
child:Text("no PDF"));
}
}
)
A fix in PODO worked for me.
Here's solution for my problem :)
pdf: json['fields']['PDF'] == null ? null : json['fields']['PDF'][0]['url'] as String,
I have the following JSON scalar:
"""
The `JSON` scalar type represents JSON values as specified by [ECMA-404](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf).
"""
scalar JSON
which I am trying to convert since my query is accepting input: JSON. When testing using graphql playground, query is JSON object thus the following works:
query {
carts(where: {
owner:{id: "xxx"}
store:{name: "yyy"}
}) {
id
}
}
# query is the starting from the where: {...}
# build.yaml
# build.yaml
gql_build|schema_builder: #same for gql_build|schema_builder + gql_build|var_builder + ferry_generator|req_builder:
options:
type_overrides:
DateTime:
name: DateTime
JSON:
name: BuiltMap<String, dynamic>
import: 'package:built_collection/built_collection.dart'
gql_build|serializer_builder:
enabled: true
options:
schema: myapp|lib/graphql/schema.graphql
custom_serializers:
- import: 'package:myapp/app/utils/builtmapjson_serializer.dart'
name: BuiltMapJsonSerializer
This is the custom serializer (builtmapjson_serializer.dart)
//// lib/app/utils/builtmapjson_serializer.dart
import 'package:built_collection/built_collection.dart';
import "package:gql_code_builder/src/serializers/json_serializer.dart";
class BuiltMapJsonSerializer extends JsonSerializer<BuiltMap<String, dynamic>> {
#override
BuiltMap<String, dynamic> fromJson(Map<String, dynamic> json) {
print('MyJsonSerializer fromJson: $json');
return BuiltMap.of(json);
}
#override
Map<String, dynamic> toJson(BuiltMap<String, dynamic> operation) {
print('MyJsonSerializer toJson: ${operation.toString()}');
return operation.asMap();
}
}
and the usage:
Future testQuery() async {
Map<String, dynamic> queryMap = {
"where": {
"owner": {
"id": "xxx",
"store": {"name": "yyy"}
}
}
};
final req = GFindCartsReq((b) {
return b..vars.query.addAll(queryMap);
});
var resStream = _graphQLService.client.request(req);
var res = await resStream.first;
print(
'linkExceptions: ${res.linkException}'); // Map: LinkException(Bad state: No serializer for '_InternalLinkedHashMap<String, Map<String, Object>>'.)
}
So whenever I try to query, it is throwing the linkException stated in the comment on the last line of usage. Any idea what should be the way of serializing it?
// Write query like this
query FindCarts($owner_id: String!, $store_name: String!) {
carts(where: {
owner:{id: $owner_id}
store:{name: $store_name}
}) {
id
}
}
// And make request like this:
final req = GFindCartsReq((b) => b..vars.store_name = 'XXX'..vars.owner_id = 'YYY');
I think you may be misunderstanding the use case. they are there to serialize and deserialize the response if you want to end up with a Dart object that's different from graphql representation. you may want to try rereading this section:
https://ferrygraphql.com/docs/custom-scalars/#create-a-custom-serializer
in the example in the docs, the graphql schema returns an int for the timestamp, but we want to actually use a Date object, so that's the purpose of the serializer. it tells ferry to deserialize the int in our responses to a Date so we can use a Date in our dart code. you could still use a json serializer (like in the examples you linked to) but it still would not be in the way you're trying to use it -- it would be if your schema returns a json string and you want to deserialize the json string. for example, in my case, my graphql schema actually does return a "jsonb" type on some objects. in order to handle that, i'm using built_value's default json_object like this:
(
...
type_overrides:
jsonb:
name: JsonObject
import: "package:built_value/json_object.dart"
custom_serializers:
- import: "package:built_value/src/json_object_serializer.dart"
name: JsonObjectSerializer
I am calling an Api that returns data in XMl
I then convert it from XML to Json using Xml2Json, to then decode and acheive a JsonMap, which is returning a map well.
When I then go to do locations.fromJson to be able to call data from my model is is returning as null.
I guess converting from XML may complicate but I have tried all possibilities, parsing the entire response, the section I need and modifying the model in all the ways I could.
The data is returning fine as Json, but there is just some disconnect when parsing it with my model, made via quicktype.io
When I call it in any way, be it print or a data retrieval, it returns on null at vehicleActivity
The call
Future<Locations> fetchLiveLocations() async {
var client = http.Client();
var locations;
Xml2Json xml2Json = new Xml2Json();
try{
var response = await client.get(
'https_call');
if (response.statusCode == 200) {
xml2Json.parse(response.body);
var jsonString = xml2Json.toGData();
var jsonMap = json.decode(jsonString);
//jsonMap is returning fine
locations = Locations.fromJson(jsonMap);
//Returning as null
}
} catch(Exception) {
return locations;
}
return locations;
}
Top part of Json Model
import 'dart:convert';
Locations locationsFromJson(String str) => Locations.fromJson(json.decode(str));
String locationsToJson(Locations data) => json.encode(data.toJson());
class Locations {
Locations({
this.vehicleActivity,
});
List<VehicleActivity> vehicleActivity;
factory Locations.fromJson(Map<String, dynamic> json) => Locations(
vehicleActivity: List<VehicleActivity>.from(json["VehicleActivity"].map((x) => VehicleActivity.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"VehicleActivity": List<dynamic>.from(vehicleActivity.map((x) => x.toJson())),
};
}
class VehicleActivity {
VehicleActivity({
this.recordedAtTime,
this.itemIdentifier,
this.validUntilTime,
this.monitoredVehicleJourney,
this.extensions,
});
DateTime recordedAtTime;
String itemIdentifier;
DateTime validUntilTime;
MonitoredVehicleJourney monitoredVehicleJourney;
Extensions extensions;
factory VehicleActivity.fromJson(Map<String, dynamic> json) => VehicleActivity(
recordedAtTime: DateTime.parse(json["RecordedAtTime"]),
itemIdentifier: json["ItemIdentifier"],
validUntilTime: DateTime.parse(json["ValidUntilTime"]),
monitoredVehicleJourney: MonitoredVehicleJourney.fromJson(json["MonitoredVehicleJourney"]),
extensions: Extensions.fromJson(json["Extensions"]),
);
XML File Returned
<Siri xmlns="http://www.siri.org.uk/siri" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.siri.org.uk/siri http://www.siri.org.uk/schema/2.0/xsd/siri.xsd" version="2.0">
<ServiceDelivery>
<ResponseTimestamp>2021-12-03T18:11:05.408806+00:00</ResponseTimestamp>
<ProducerRef>ItoWorld</ProducerRef>
<VehicleMonitoringDelivery>
<ResponseTimestamp>2021-12-03T18:11:05.408806+00:00</ResponseTimestamp>
<RequestMessageRef>5747b24f</RequestMessageRef>
<ValidUntil>2021-12-03T18:16:05.408806+00:00</ValidUntil>
<ShortestPossibleCycle>PT5S</ShortestPossibleCycle>
<VehicleActivity>
<RecordedAtTime>2021-12-03T18:10:01+00:00</RecordedAtTime>
<ItemIdentifier>ad2c7031-ceac-4e7c-bc0c-9e667ad00dfe</ItemIdentifier>
<ValidUntilTime>2021-12-03T18:16:05.408968</ValidUntilTime>
<MonitoredVehicleJourney>
<LineRef>4</LineRef>
<DirectionRef>inbound</DirectionRef>
<FramedVehicleJourneyRef>
<DataFrameRef>2021-12-03</DataFrameRef>
<DatedVehicleJourneyRef>4_20211203_18_04</DatedVehicleJourneyRef>
</FramedVehicleJourneyRef>
<PublishedLineName>4</PublishedLineName>
<OperatorRef>FTVA</OperatorRef>
<DestinationRef>03700324</DestinationRef>
<VehicleLocation>
<Longitude>-0.719601</Longitude>
<Latitude>51.520305</Latitude>
</VehicleLocation>
<Bearing>30.0</Bearing>
<BlockRef>801312</BlockRef>
<VehicleRef>69921</VehicleRef>
</MonitoredVehicleJourney>
<Extensions>
<VehicleJourney>
<Operational>
<TicketMachine>
<TicketMachineServiceCode>B4</TicketMachineServiceCode>
<JourneyCode>1815</JourneyCode>
</TicketMachine>
</Operational>
<VehicleUniqueId>69921</VehicleUniqueId>
<DriverRef>801312</DriverRef>
</VehicleJourney>
</Extensions>
</VehicleActivity>
Here's an example VehicleActivity class - note that it doesn't handle any errors like missing XML tags or unparsable dates, which you should add yourself.
class VehicleActivity {
VehicleActivity({
this.recordedAtTime,
this.itemIdentifier,
this.validUntilTime,
});
DateTime? recordedAtTime;
String? itemIdentifier;
DateTime? validUntilTime;
factory VehicleActivity.fromElement(XmlElement vaElement) => VehicleActivity(
recordedAtTime: DateTime.parse(
vaElement.findElements('RecordedAtTime').first.text,
),
itemIdentifier: vaElement.findElements('ItemIdentifier').first.text,
validUntilTime: DateTime.parse(
vaElement.findElements('ValidUntilTime').first.text,
),
);
}
You would use the factory method from the enclosing tag (similar to how your JSON parsers are written), for each of the vehicle activity tags it finds. (Note that XML can have multiple identically named tags, which is why the code is using first to find the (hopefully) one and only tag. If you want to parse XML correctly you need to deal with this - and note that the trip through JSON could break this - but not with your simple schema.)
Here's a simple example that just finds all the vehicle activity tags:
final doc = XmlDocument.parse(utf8.decode(response.bodyBytes));
final allActivities = doc
.findAllElements('VehicleActivity')
.map((e) => VehicleActivity.fromElement(e))
.toList();
print(allActivities);
Can anyone tell me how to parse arrays of object in flutter. When I am parsing the json I am getting error as List is not a subtype of type Map<String, dynamic>.
Below is my json file which needs to be parsed. Please help me to fix this issue.
[
{
"empPayslipsId": "2021012000440",
"month": "Jan",
"description": "Payslip for JAN 2021 (Month End)",
"paymentPeriod": "1/1/2021 12:00:00 AM - 1/31/2021 12:00:00 AM",
"lastAccessBy": "0002\r\n118.200.199.70",
"lastAccessDate": "20210202",
"lastAccessTime": "105706",
"successAccess": "2",
"failAccess": "2"
}
]
Future<void> loadQueryPeriod(int year, var month) async {
String baseURL = '${domainURL}api/PaySlip?year=$year&month=$month';
try {
final response = await http.get(baseURL, headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization':
'Bearer ${Provider.of<UserVM>(navigatorKey.currentContext, listen: false).accessToken}',
});
print('UIC PDF response : ${response.body}');
print(
'UIC Token response : ${Provider.of<UserVM>(navigatorKey.currentContext, listen: false).accessToken}');
if (response.statusCode == 200) {
final Map<String, dynamic> data = json.decode(response.body);
print('result type: ${data.runtimeType}');
}
} catch (e) {
print(e);
throw Exception('Download PDF Fail! ${e.toString()}');
}
}
}
Change it to this:
final Map<String, dynamic> data = json.decode(response.body)[0];
This is because your map is inside a list. Look at the square brackets [ ] enclosing your map. The map that you need, is at index[0] of this list.
use this podo class :
// Generated by https://quicktype.io
// To parse this JSON data, do
//
// final sample = sampleFromJson(jsonString);
import 'dart:convert';
List<Sample> sampleFromJson(String str) {
final jsonData = json.decode(str);
return new List<Sample>.from(jsonData.map((x) => Sample.fromJson(x)));
}
String sampleToJson(List<Sample> data) {
final dyn = new List<dynamic>.from(data.map((x) => x.toJson()));
return json.encode(dyn);
}
class Sample {
String empPayslipsId;
String month;
String description;
String paymentPeriod;
String lastAccessBy;
String lastAccessDate;
String lastAccessTime;
String successAccess;
String failAccess;
Sample({
this.empPayslipsId,
this.month,
this.description,
this.paymentPeriod,
this.lastAccessBy,
this.lastAccessDate,
this.lastAccessTime,
this.successAccess,
this.failAccess,
});
factory Sample.fromJson(Map<String, dynamic> json) => new Sample(
empPayslipsId: json["empPayslipsId"],
month: json["month"],
description: json["description"],
paymentPeriod: json["paymentPeriod"],
lastAccessBy: json["lastAccessBy"],
lastAccessDate: json["lastAccessDate"],
lastAccessTime: json["lastAccessTime"],
successAccess: json["successAccess"],
failAccess: json["failAccess"],
);
Map<String, dynamic> toJson() => {
"empPayslipsId": empPayslipsId,
"month": month,
"description": description,
"paymentPeriod": paymentPeriod,
"lastAccessBy": lastAccessBy,
"lastAccessDate": lastAccessDate,
"lastAccessTime": lastAccessTime,
"successAccess": successAccess,
"failAccess": failAccess,
};
}
Now inorder to parse json call,
Sample sample = sampleFromJson(jsonString);
via this you will get the access to sample PODO class and you can access any object you want.
The initial data you received by calling a get request isn't stored in a map, but rather in a list.
You should do something like this to receive your initial data.
if (response.statusCode == 200) {
final List<dynamic> data = json.decode(response.body);
}
From there, they're numerous ways to get the data from your data variable. You can use lists here if you want, for example to get the value of month in the JSON.
final String month = data[0]['month'];
If you'd prefer to use Maps, the syntax it'll look like this
final Map<String, dynamic> endpointData = data[0];
final String responseKey = 'month';
final var result = endpointData[responseKey];
if you have data model you can do it like this
fromJsonList(List<dynamic> jsonList) {
List<YourModel> yourModelList = [];
jsonList.forEach((jsonModel) {
menuModelsOfferList.add(YourModel.fromJson(jsonModel));
});
i have class that generate json list this is my class
class Tool{
String Name;
bool selection;
String englishName;
Map<String, dynamic> toJson() {
return {
'Name': persianName,
'selection': selection,
'englishName': englishName
};
}
}
List<Tool> tools=new List();
setTool(tool){
tools.add(tool);
}
toolsLength(){
return tools.length;
}
updatetool(index,goal){
tools[index]=goal;
}
getTool(index){
return tools[index];
}
getAllTools(){
return tools;
}
and this is dio library that send my list to server every thing is ok but my array is into Double quotation in other word my list is string how to pick up double quotation around of json array . if assume my json array hase
"tools": [{"name":"jack","selection" : false " ,"englishName":"jock"}]
result is :
"tools": "[{"name":"jack","selection" : false " ,"englishName":"jock"}]"
how fix it this is my class for send
FormData formData = new FormData.from({
"tools":jsonEncode(getAllTools().map((e) => e.toJson()).toList()) ,
});
response = await
dio.post("${strings.baseurl}/analyze/$username/$teacher", data:
formData);
print("----------> response is :"+response.toString());
Edit
You can paste the following code to DarPad https://dartpad.dartlang.org/
The following demo shows transform your Json String to Tool List and Convert your Tool List to JSON string again and use map.toJson
var yourresult = toolList.map((e) => e.toJson()).toList();
you can see result in picture
use FormData.from need to know what your api's correct JSON String.
Please test your web api with Postman, if you success, you will know correct format string.
In your code
FormData formData = new FormData.from({
"tools":jsonEncode(getAllTools().map((e) => e.toJson()).toList()) ,
});
if you are trying to to do
FormData formData = new FormData.from({
"tools":'[{"name":"jack","selection" : false ,"englishName":"jock"}, {"name":"jack2","selection" : false ,"englishName":"jock2"}]' ,
});
so you can get your json string first and put it in FormData
var toolsJson = toolsToJson(toolList);
FormData formData = new FormData.from({
"tools":toolsJson ,
});
full demo code, you can paste to DartPad to see string and list conversion
import 'dart:async';
import 'dart:io';
import 'dart:core';
import 'dart:convert';
class Tools {
String name;
bool selection;
String englishName;
Tools({
this.name,
this.selection,
this.englishName,
});
factory Tools.fromJson(Map<String, dynamic> json) => new Tools(
name: json["name"],
selection: json["selection"],
englishName: json["englishName"],
);
Map<String, dynamic> toJson() => {
"name": name,
"selection": selection,
"englishName": englishName,
};
}
main() {
List<Tools> toolsFromJson(String str) => new List<Tools>.from(json.decode(str).map((x) => Tools.fromJson(x)));
String toolsToJson(List<Tools> data) => json.encode(new List<dynamic>.from(data.map((x) => x.toJson())));
var toolsStr = '[{"name":"jack","selection" : false ,"englishName":"jock"}, {"name":"jack2","selection" : false ,"englishName":"jock2"}]';
var toolList = toolsFromJson(toolsStr);
var toolsJson = toolsToJson(toolList);
print("toolsJson ${toolsJson} \n");
var toolsmap = toolList[0].toJson();
print("toolsmap ${toolsmap.toString()}\n");
var yourresult = toolList.map((e) => e.toJson()).toList();
print(yourresult.toString());
}
you can paste your JSON string to https://app.quicktype.io/, you will get correct Dart class
correct JSON string of your sample. in false keyword followed by a " cause JSON string parsing error.
[
{"name":"jack",
"selection" : false ,
"englishName":"jock"
}
]
code to parse JSON string and encode to List, use toJson will convert to JSON string you need to send with dio form
// To parse this JSON data, do
//
// final tools = toolsFromJson(jsonString);
import 'dart:convert';
List<Tools> toolsFromJson(String str) => new List<Tools>.from(json.decode(str).map((x) => Tools.fromJson(x)));
String toolsToJson(List<Tools> data) => json.encode(new List<dynamic>.from(data.map((x) => x.toJson())));
class Tools {
String name;
bool selection;
String englishName;
Tools({
this.name,
this.selection,
this.englishName,
});
factory Tools.fromJson(Map<String, dynamic> json) => new Tools(
name: json["name"],
selection: json["selection"],
englishName: json["englishName"],
);
Map<String, dynamic> toJson() => {
"name": name,
"selection": selection,
"englishName": englishName,
};
}