import 'dart:convert';
main() async {
// json 转化为 map
String jsonStr = '''
[
{"name": "ajanuw"},
{"name": "suou"}
]
''';
var jsonObj = jsonDecode(jsonStr);
print(jsonObj[0]['name'] == 'ajanuw'); // true
// list<Map> 转化为 json字符串
var scores = [
{'score': 40},
{'score': 80},
{'score': 100, 'overtime': true, 'special_guest': null}
];
var jsonText = jsonEncode(scores);
print(jsonText);
}
使用对象添加模板 JSON to Dart
import 'dart:convert';
class MyInfo {
MyInfo({this.age, this.name});
String name;
int age;
factory MyInfo.fromJson(Map<String, dynamic> jsonMap) {
return MyInfo(
name: jsonMap['name'],
age: jsonMap['age'],
);
}
}
main(List<String> args) {
String jsonStr = '''
{
"name": "ajanuw",
"age": 12
}
''';
var parsed = jsonDecode(jsonStr);
MyInfo data = MyInfo.fromJson(parsed);
print(data.age);
}
使用“built_value”库来处理json
我在这里使用"stagehand console-full"创建的项目示例，项目名叫"dart_test"
1） 安装依赖
dependencies:
...
built_value:
built_collection:
dev_dependencies:
...
build_runner:
built_value_generator:
- 准备json数据
{
"id": 157538,
"date": "2017-07-21T10:30:34",
"date_gmt": "2017-07-21T17:30:34",
"type": "post",
"link": "https://example.com",
"title": {
"rendered": "Json 2 dart built_value converter"
},
"tags": [
1798,
6298
]
}
- 创建文件"lib/models/hello.dart"，文件名很重要必须要要和你的class名一样
import 'dart:convert';
import 'package:built_collection/built_collection.dart';
import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';
part 'hello.g.dart';
abstract class Hello implements Built<Hello, HelloBuilder> {
Hello._();
factory Hello([updates(HelloBuilder b)]) = _$Hello;
@BuiltValueField(wireName: 'id')
int get id;
@BuiltValueField(wireName: 'date')
String get date;
@BuiltValueField(wireName: 'date_gmt')
String get dateGmt;
@BuiltValueField(wireName: 'type')
String get type;
@BuiltValueField(wireName: 'link')
String get link;
@BuiltValueField(wireName: 'title')
Title get title;
@nullable // 可为空，返回null
@BuiltValueField(wireName: 'tags')
BuiltList<int> get tags;
String toJson() {
return jsonEncode(serializers.serializeWith(Hello.serializer, this));
}
static Hello fromJson(String jsonString) {
return serializers.deserializeWith(
Hello.serializer, jsonDecode(jsonString));
}
static Serializer<Hello> get serializer => _$helloSerializer;
}
abstract class Title implements Built<Title, TitleBuilder> {
Title._();
factory Title([updates(TitleBuilder b)]) = _$Title;
@BuiltValueField(wireName: 'rendered')
String get rendered;
String toJson() {
return jsonEncode(serializers.serializeWith(Title.serializer, this));
}
static Title fromJson(String jsonString) {
return serializers.deserializeWith(
Title.serializer, jsonDecode(jsonString));
}
static Serializer<Title> get serializer => _$titleSerializer;
}
- 保存文件后，在项目根目录下运行命令, 生成"lib/models/hello.g.dart"文件
flutter packages pub run build_runner build // 执行一次build命令
flutter packages pub run build_runner watch // 文件更改自动build
flutter packages pub run build_runner watch --delete-conflicting-outputs // 删除旧文件在build
- 创建"lib/models/serializers.dart"文件，编写下面的代码后，保存会生成"lib/models/serializers.g.dart"文件
import 'package:built_collection/built_collection.dart';
import 'package:built_value/serializer.dart';
import 'package:built_value/standard_json_plugin.dart';
import 'package:dart_test/models/hello.dart';
part 'serializers.g.dart';
@SerializersFor(const [
Hello
])
final Serializers serializers = (_$serializers.toBuilder()..addPlugin(StandardJsonPlugin())).build();
- 编写“bin/main.dart"
import 'package:dart_test/models/hello.dart';
String jsonStr = '''
{
"id": 157538,
"date": "2017-07-21T10:30:34",
"date_gmt": "2017-07-21T17:30:34",
"type": "post",
"link": "https://example.com",
"title": {
"rendered": "Json 2 dart built_value converter"
},
"tags": [
1798,
6298
]
}
''';
main(List<String> args) {
Hello hello = Hello.fromJson(jsonStr);
print(hello.title.rendered);
print(hello.tags.length);
}
- 保存文件后执行
> dart bin/main.dart
Json 2 dart built_value converter
2
在vscode中隐藏 “*.g.dart”生成的文件
"files.exclude": {
"**/*.g.dart": true
}
built_value处理json不要有这样的数据 { key: [[{}], [{}],...] } 转换为这样: { key: [{key: []}, {key: []},...] }
创建枚举
int get age;
TypeStatus get type => age < 10 ? TypeStatus.a : TypeStatus.b;
enum TypeStatus {
a,
b,
}
// or
class TypeStatus extends EnumClass {
static const TypeStatus a = _$a;
static const TypeStatus b = _$b;
const TypeStatus._(String name) : super(name);
static BuiltSet<TypeStatus> get values => _$values;
static TypeStatus valueOf(String name) => _$valueOf(name);
}
手动创建dto模型
import 'dto/hello_dto/hello_dto.dart';
String jsonStr = '''
{
"id": 157538,
"date": "2017-07-21T10:30:34",
"date_gmt": "2017-07-21T17:30:34",
"type": "post",
"link": "https://example.com",
"title": {
"rendered": "Json 2 dart built_value converter"
},
"tags": [
1798,
6298
]
}
''';
main(List<String> args) {
var r = HelloDto(
(b) => b
..id = 1
..date = 'date'
..dateGmt = 'dateGmt'
..type = 'get'
..link = 'link'
..title.rendered = 'title'
..tags.addAll([1, 2]),
);
print(r);
}
λ dart test.dart
HelloDto {
id=1.0,
date=date,
dateGmt=dateGmt,
type=get,
link=link,
title=TitleDto {
rendered=title,
},
tags=[1, 2],
arrobj=[],
}
rebuild重建实例
var hello = HelloDto.fromJson(jsonStr);
var hello2 = hello.rebuild((b) => b.type = 'get');
print(hello == hello2); // false
// 数据一样是相等的
var hello = HelloDto.fromJson(jsonStr);
var hello2 = HelloDto.fromJson(jsonStr);
print(hello == hello2); // true
在flutter中更新数据
import 'package:flutter/material.dart';
import 'package:flutter_demo/dto/hello_dto/hello_dto.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: HomePage(),
);
}
}
class HomePage extends StatefulWidget {
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
List<HelloDto> data;
@override
void initState() {
super.initState();
data = HelloDto.fromListJson('''[{"a":"a1","b":"b1"},{"a":"a2","b":"b2"}]''');
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Home Page'),
),
body: ListView(
children: <Widget>[
for (var it in data)
ListTile(
title: Text(it.a),
subtitle: Text(it.b),
),
],
),
floatingActionButton: FloatingActionButton(
onPressed: () {
setState(() {
data[0] = data[0].rebuild((b) => b.a = 'new title');
});
},
child: Icon(Icons.hot_tub),
),
);
}
}
为可能为null的数据设置默认值
@nullable
@BuiltValueField()
int get id;
static HelloDto fromJson(String jsonString) {
return serializers
.deserializeWith(HelloDto.serializer, jsonDecode(jsonString))
.rebuild(
// 在这里设置
(b) => b..id ??= 0,
);
}
var hello = HelloDto.fromJson('{"id": null}');
print(hello);
print(hello.id); //=> 0