由于Flutter从它的SDK中取出了dart：mirror,因此不再可能像dartson这样的库使用
JSON来对象序列化/反序列化.但是我读过build_value是达到类似目的的另一种方式.我找不到任何关于如何实施它的好例子,因为它包含大量的锅炉板代码.有人能举个例子吗？例如,这是我正在尝试序列化到对象的JSON：
{
"name":"John","age":30,"cars": [
{ "name":"Ford","models":[ "Fiesta","Focus","Mustang" ] },{ "name":"BMW","models":[ "320","X3","X5" ] },{ "name":"Fiat","models":[ "500","Panda" ] }
]
}
解决方法
我希望从提供的答案中获得更多细节.尽管它们是很好的建议,但它们对我来说太过普遍了解.所以在做了我自己的研究之后,我将把我的实现分享给我提供的上述JSON示例,希望它可以节省别人的时间.以下是我遵循的步骤：
>在我的Flutter项目中,首先我导入了以下库：
dependencies:
built_value: ^1.0.1
built_collection: ^1.0.0dev_dependencies:
build_runner: ^0.3.0
built_value_generator:^1.0.1
>我创建了一个名为tool的文件夹.在其中,我放了2个文件：build.dart和watch.dart.这些文件的实现如下所示
build.dart
// copyright (c) 2015,Google Inc. Please see the AUTHORS file for details.
// All rights reserved. Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
import 'dart:async';
import 'package:build_runner/build_runner.dart';
import 'package:built_value_generator/built_value_generator.dart';
import 'package:source_gen/source_gen.dart';
/// Example of how to use source_gen with [BuiltValueGenerator].
///
/// Import the generators you want and pass them to [build] as shown,/// specifying which files in which packages you want to run against.
Future main(List<String> args) async {
await build(
new PhaseGroup.singleAction(
new GeneratorBuilder([new BuiltValueGenerator()]),new InputSet('built_value_example',const [
'lib/model/*.dart','lib/*.dart',])),deleteFilesByDefault: true);
}
watch.dart
// copyright (c) 2016,Google Inc. Please see the AUTHORS file for details.
// All rights reserved. Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
import 'dart:async';
import 'package:build_runner/build_runner.dart';
import 'package:built_value_generator/built_value_generator.dart';
import 'package:source_gen/source_gen.dart';
/// Example of how to use source_gen with [BuiltValueGenerator].
///
/// This script runs a watcher that continuously rebuilds generated source.
///
/// Import the generators you want and pass them to [watch] as shown,/// specifying which files in which packages you want to run against.
Future main(List<String> args) async {
watch(
new PhaseGroup.singleAction(
new GeneratorBuilder([new BuiltValueGenerator()]),'lib/*.dart'])),deleteFilesByDefault: true);
}
>我创建了一个serializers.dart文件,它将我的json字符串序列化为我的自定义dart对象,以及我的模型对象person.dart
serializers.dart
library serializers;
import 'package:built_collection/built_collection.dart';
import 'package:built_value/serializer.dart';
import 'package:built_value/standard_json_plugin.dart';
import 'model/person.dart';
part 'serializers.g.dart';
Serializers serializers = (
_$serializers.toBuilder()..addplugin(new StandardJsonPlugin())
).build();
person.dart
library person;
import 'package:built_collection/built_collection.dart';
import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';
part 'person.g.dart';
abstract class Person implements Built<Person,PersonBuilder> {
String get name;
int get age;
BuiltList<Car> get cars;
Person._();
factory Person([updates(PersonBuilder b)]) = _$Person;
static Serializer<Person> get serializer => _$personSerializer;
}
abstract class Car implements Built<Car,CarBuilder> {
String get name;
BuiltList<String> get models;
Car._();
factory Car([updates(CarBuilder b)]) = _$Car;
static Serializer<Car> get serializer => _$carSerializer;
}
>创建上面的4个文件后,它将显示一些编译器错误.不要介意他们.这是因为build.dart文件尚未运行.因此,在此步骤中,运行build.dart.如果您正在使用Webstorm,只需右键单击build.dart并点击“Run build.dart”即可.这将创建2个文件：“person.g.dart”和“serializers.g.dart”.如果您仔细注意,在我们的build.dart文件中,我们将’lib / model / .dart’和’lib / .dart’放在一起.构建通过遍历指定的路径知道在哪里查找这些文件,并查找包含部分“内容”的文件.因此,在运行build.dart文件之前,将该行保留在这些文件中非常重要
>最后,现在我可以在main.dart文件中使用序列化程序将json字符串序列化为我的自定义dart对象类Person.在我的main.dart中,我在initState()中添加了以下代码
main.dart
Person _person;
@override
void initState() {
super.initState();
String json = "{"
"\"name\":\"John\",\"age\":30,\"cars\": "
"["
"{ \"name\":\"Ford\",\"models\":[ \"Fiesta\",\"Focus\",\"Mustang\" ] },"
"{ \"name\":\"BMW\",\"models\":[ \"320\",\"X3\",\"X5\" ] },"
"{ \"name\":\"Fiat\",\"models\":[ \"500\",\"Panda\" ] }"
"]}";
setState(() {
_person = serializers.deserializeWith(
Person.serializer,JSON.decode(json));
});
}
我的示例项目也可以在Github Built value sample project上获得