在dart中是否可以从字符串中实例化一个类?
例如:
var myObject = window[classNameString];
id myclass = [[NSClassFromString(@"MyClass") alloc] init];
您需要知道库名称和类名称才能使其正常工作。假设您都知道,下面的示例将实例化TestClass
并在其上调用doStuff
。
library test;
import "dart:mirrors";
class TestClass {
doStuff() => print("doStuff was called!");
}
main() {
MirrorSystem mirrors = currentMirrorSystem();
LibraryMirror lm = mirrors.libraries['test'];
ClassMirror cm = lm.classes['TestClass'];
Future tcFuture = cm.newInstance('', []);
tcFuture.then((InstanceMirror im) {
var tc = im.reflectee;
tc.doStuff();
});
}
关于这个解决方案的几点说明:
语法已更改。我这样做了
library test;
import "dart:mirrors";
class TestClass {
doStuff() => print("doStuff was called!");
}
main() {
MirrorSystem mirrors = currentMirrorSystem();
LibraryMirror lm = mirrors.libraries.values.firstWhere(
(LibraryMirror lm) => lm.qualifiedName == new Symbol('test'));
ClassMirror cm = lm.declarations[new Symbol('TestClass')];
InstanceMirror im = cm.newInstance(new Symbol(''), []);
var tc = im.reflectee;
tc.doStuff();
}
如果有更多的库名为'test',那么这将失败。
这是一个困扰我的问题,直到我认为我可以实现一个粗略的方法来处理编码的Json对象/字符串或Dart映射到所需类的转换。
下面是一个简单的例子,它也处理空值并接受JSON(作为字符串参数)
import 'dart:convert';
class PaymentDetail
{
String AccountNumber;
double Amount;
int ChargeTypeID;
String CustomerNames;
PaymentDetail({
this.AccountNumber,
this.Amount,
this.ChargeTypeID,
this.CustomerNames
});
PaymentDetail from ({ string : String, object : Map }) {
var map = (object==null) ? (string==null) ? Map() : json.decode(string) : (object==null) ? Map() : object;
return new PaymentDetail(
AccountNumber : map["AccountNumber"] as String,
Amount : map["Amount"] as double,
ChargeTypeID : map["ChargeTypeID"] as int,
CustomerNames : map["CustomerNames"] as String
);
}
}
以下是它的实现
PaymentDetail payDetail = new PaymentDetail().from(object: new Map());
PaymentDetail otherPayDetail = new PaymentDetail().from(object: {"AccountNumber": "1234", "Amount": 567.2980908});
再一次,这在整个项目中克隆是简单而乏味的,但它适用于简单的情况。