如何通过字段访问JSON ?

Question

有一个JSON

jsonData

{
"data": {
"splashPage": {
"title": "Splash"
},
"homePage": {
"title": "Home"
}
}
}

List<String> accessField = ['data','splashPage']; 
final out = accessField.map((e) => "['$e']").join();
Map jsonMapData = jsonDecode(jsonData); 
Map<String, dynamic> splashPageJson = '${jsonMapData}$out' as Map<String, dynamic>; 
print(splashPageJson);

我得到一个错误，不能访问splashPage.

_CastError (type 'String' is not a subtype of type 'Map<String, dynamic>' in type cast)

如何从JSON访问splashPage ?

注意:accessField是动态值

如果我想访问splashPage，声明

accessField = ['data','splashPage'];

如果我想访问主页，声明

accessField = ['data','homePage'];

Answer 1

这是你想要的吗?

var jsonData = {
"data": {
"splashPage": {
"title": "Splash"
},
"homePage": {
"title": "Home"
}
}
}
Map jsonMapData = jsonDecode(jsonData); 
List<String> accessField = ['data','splashPage'];
Map<String, dynamic> requiredResult = jsonMapData[accessField[0]][accessField[1]];

Answer 2

解决方案如下:

第一进口:

import 'dart:convert';

将JSON存储到映射中:

final Map<String, dynamic> map = json.decode('{"data":{"splashPage":{"title":"Splash"},"homePage":{"title":"Home"}}}');

打印您的需求:

print(map["data"]["splashPage"]["title"]);

Answer 3

模型代码:

class Model {
Model({
this.data,
});
Model.fromJson(Map<String, dynamic> json) {
data = json["data"] != null ? Data.fromJson(json["data"]) : null;
}
Data? data;
Map<String, dynamic> toJson() {
final Map<String, dynamic> map = <String, dynamic>{};
if (data != null) {
map["data"] = data?.toJson();
}
return map;
}
}
class Data {
Data({
this.splashPage,
this.homePage,
});
Data.fromJson(Map<String, dynamic> json) {
splashPage = json["splashPage"] != null
? SplashPage.fromJson(json["splashPage"])
: null;
homePage =
json["homePage"] != null ? HomePage.fromJson(json["homePage"]) : null;
}
SplashPage? splashPage;
HomePage? homePage;
Map<String, dynamic> toJson() {
final Map<String, dynamic> map = <String, dynamic>{};
if (splashPage != null) {
map["splashPage"] = splashPage?.toJson();
}
if (homePage != null) {
map["homePage"] = homePage?.toJson();
}
return map;
}
}
class HomePage {
HomePage({
this.title,
});
HomePage.fromJson(Map<String, dynamic> json) {
title = json["title"];
}
String? title;
Map<String, dynamic> toJson() {
final Map<String, dynamic> map = <String, dynamic>{};
map["title"] = title;
return map;
}
}
class SplashPage {
SplashPage({
this.title,
});
SplashPage.fromJson(Map<String, dynamic> json) {
title = json["title"];
}
String? title;
Map<String, dynamic> toJson() {
final Map<String, dynamic> map = <String, dynamic>{};
map["title"] = title;
return map;
}
}

供您使用的代码:

final Model model = Model.fromJson(
json.decode(
'{"data":{"splashPage":{"title":"Splash"},"homePage":{"title":"Home"}}}',
),
);

print(model.data?.splashPage?.title ?? "");
print(model.data?.homePage?.title ?? "");

不要忘记导入:

import 'dart:convert';

Answer 4

• 这是一个关于Json数据格式转换为本地数据模型的问题。如果你早点发布Json数据，问题可能不会那么复杂
• 试试这个。

void test() {
var json =
'{"data":{"splashPage":{"title":"Splash"},"homePage":{"title":"Home"}}}';
var map = jsonDecode(json) as Map<String, dynamic>;
var model = DataResponseModel.fromJson(map);
pr(model.data?.homePage?.title); // Home
pr(model.data?.splashPage?.title); // Splash
}

class TitleModel {
String? title;
TitleModel({required this.title});
factory TitleModel.fromJson(Map<String, dynamic> map) =>
TitleModel(title: map['title']);
}
class DataModel {
TitleModel? splashPage;
TitleModel? homePage;
DataModel({required this.splashPage, this.homePage});
factory DataModel.fromJson(Map<String, dynamic> map) => DataModel(
splashPage: TitleModel.fromJson(map['splashPage']),
homePage: TitleModel.fromJson(map['homePage']),
);
}
class DataResponseModel {
DataModel? data;
DataResponseModel({required this.data});
factory DataResponseModel.fromJson(Map<String, dynamic> map) =>
DataResponseModel(
data: DataModel.fromJson(map['data']),
);
}