I have the following code (simplified), that uses reflection to iterate a class's fields and getters and output the values. The ContainsGetter
class contains a getter, and the ContainsField
class contains a simple field.
Using dart:mirrors
library, I can get the value of the field by using instanceMirror.getField(fieldName)
), but not the getter by using instanceMirror.invoke(fieldName,[])
.
The following Dart script (using the build 17463) gives the output below:
app script
import 'dart:mirrors';
class ContainsGetter { // raises an error
String get aGetter => "I am a getter";
}
class ContainsField { // works fine
String aField = "I am a field";
}
void main() {
printFieldValues(reflect(new ContainsField()));
printGetterValues(reflect(new ContainsGetter()));
}
void printFieldValues(instanceMirror) {
var classMirror = instanceMirror.type;
classMirror.variables.keys.forEach((key) {
var futureField = instanceMirror.getField(key); // <-- works ok
futureField.then((imField) => print("Field: $key=${imField.reflectee}"));
});
}
void printGetterValues(instanceMirror) {
var classMirror = instanceMirror.type;
classMirror.getters.keys.forEach((key) {
var futureValue = instanceMirror.invoke(key,[]); // <-- fails
futureValue.then((imValue) => print("Field: $key=${imValue.reflectee}"));
});
}
output
Field: aField=I am a field
Uncaught Error: Compile-time error during mirrored execution: <Dart_Invoke: did not find instance method 'ContainsGetter.aGetter'.>
Stack Trace:
#0 _LocalObjectMirrorImpl._invoke (dart:mirrors-patch:163:3)
#1 _LocalObjectMirrorImpl.invoke (dart:mirrors-patch:125:33)
(An acceptable could be that "this bit just hasn't been written yet!")
Aah, I've just worked it out. Although
aGetter
is like a method in its implementation, you use thegetField()
rather thaninvoke
to retrieve its value.