How would I do the Dart equivalent of this Java code?
Class<?> c = Class.forName("mypackage.MyClass");
Constructor<?> cons = c.getConstructor(String.class);
Object object = cons.newInstance("MyAttributeValue");
(From Jeff Gardner)
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3 Answers
The Dart code:
ClassMirror c = reflectClass(MyClass);
InstanceMirror im = c.newInstance(const Symbol(''), ['MyAttributeValue']);
var o = im.reflectee;
Learn more from this doc: http://www.dartlang.org/articles/reflection-with-mirrors/
(From Gilad Bracha)
1 Comment
ringstaff
Both 'first' and 'classes' properties are not on LibraryMirror any more (I'm using 30188). How would you do this with Dart v1?
Using built_mirrors you can do it next way:
library my_lib;
import 'package:built_mirrors/built_mirrors.dart';
part 'my_lib.g.dart';
@reflectable
class MyClass {
String myAttribute;
MyClass(this.myAttribute);
}
main() {
_initMirrors();
ClassMirror cm = reflectType(MyClass);
var o = cm.constructors[''](['MyAttributeValue']);
print("o.myAttribute: ${o.myattribute}");
}
Comments
This was an issue that has plagued me until I figured that I could implement a crude from method to handle the conversion of encoded Json Objects/strings or Dart Maps to the desired class.
Below is a simple example that also handles nulls and accepts JSON (as the string parameter)
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
);
}
}
Below is it's implementation
PaymentDetail payDetail = new PaymentDetail().from(object: new Map());
PaymentDetail otherPayDetail = new PaymentDetail().from(object: {"AccountNumber": "1234", "Amount": 567.2980908});
Once again, this is simplistic and tedious to clone throughout the project but it works for simple cases.
