Flutter Models to get a List of string - json

Question

I have a problem trying to make a special model with this JSON.
I actually need to get a list of organization and a list of projects.
I have no problem getting the list of projects since it's an array.
But to get the list of Organizations I admit I need help to do something like making a forEach "MyContexts" and save every Organizations in a list and return her. (Maybe this is not the best way)
Here is a example of the JSON :
{
"MyContexts": [
{
"Organisation": {
"ID": "xxx",
"Name": "xxx"
},
"Projects": [
{
"ID": "xxx",
"Name": "xxx"
}
]
}
]
}
To be more precise, I need a list of String because the value will be inserted in a DropdownFormField list of value.
I hope I have made it clear for you to understand, else you can ask me question.
Thank you in advance for your help.

Answer 1

You don't need a list of strings, you need a model from your json and list of it's objects. You need a class like this
class MyContextModel {
List<MyContexts>? myContexts;
MyContextModel({this.myContexts});
MyContextModel.fromJson(Map<String, dynamic> json) {
if (json['MyContexts'] != null) {
myContexts = <MyContexts>[];
json['MyContexts'].forEach((v) {
myContexts!.add(new MyContexts.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.myContexts != null) {
data['MyContexts'] = this.myContexts!.map((v) => v.toJson()).toList();
}
return data;
}
}
class MyContexts {
Organisation? organisation;
List<Projects>? projects;
MyContexts({this.organisation, this.projects});
MyContexts.fromJson(Map<String, dynamic> json) {
organisation = json['Organisation'] != null
? new Organisation.fromJson(json['Organisation'])
: null;
if (json['Projects'] != null) {
projects = <Projects>[];
json['Projects'].forEach((v) {
projects!.add(new Projects.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.organisation != null) {
data['Organisation'] = this.organisation!.toJson();
}
if (this.projects != null) {
data['Projects'] = this.projects!.map((v) => v.toJson()).toList();
}
return data;
}
}
class Organisation {
String? iD;
String? name;
Organisation({this.iD, this.name});
Organisation.fromJson(Map<String, dynamic> json) {
iD = json['ID'];
name = json['Name'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['ID'] = this.iD;
data['Name'] = this.name;
return data;
}
}
And then you need to make list of it, and you can show it's variables in your DropdownFormField widget like Text(object.Organisation!.name!)

Answer 2

I may be understanding it in the wrong way, but I am thinking the JSON contains a map, which values are {"Organisation": ..., "Projects": ...}. If that's not the case, you can stop reading and correct me now.
Let's say json is the variable containing the JSON structure of your example.
Then you can do
final orgs = json.values.map((context) => context['Organisation']).toList();
final projs = json.values.map((context) => context['Projects']).toList();
Or you can use forEach like you mentioned, which requires slightly more coding, but that's not much other than a style of preference. If you think a particular approach is more straightforward and more understandable, go for it.
A side note: usually we use for loops explicit instead of forEach.