I have an annotation like following:
#Arg
internal var stringArg1: String? = null
#Arg
internal var stringArg2: String = "default value"
And I iterate over all of my annotated classes variables like following:
for (e in annotatedElement.enclosedElements) {
if (e.getAnnotation(Arg::class.java) != null) {
val defaultValue = ???
}
}
Question:
Is it possible to get the default value of an annotated variable? In my example I want to retrieve null and "default value" for my two variables.
No, it's not possible.
Default values would have to be stored in Kotlin metadata for you to access them in your annotation processor (and they are not stored there).
You can see some details about that in the Kotlin repository:
Related
Thanks to #roddy for his answer to my query here
Copy pasting from earlier to set the context :
here is my data structure :
public class Premium{
private Map<String,Map<String,String>> valuesMap = new HashMap<String,Map<String,String>>();
public Map<String, Map<String, String>> getValuesMap() {
return valuesMap;
}
}
Sample values that will be present inside this 'valuesMap' :
Map<String,String> m1= new HashMap<String,String>();
m1.put("death","100");
m1.put("income","50");
valuesMap.put("Male",m1);
valuesMap.put("Female",m2);
....
Thanks to #Roddy now I can extract the map 'm1' embedded within 'valuesMap' for "Male"
rule "rule#7 testing me 001 "
when
// below line extracts 'valuesMap' from Premium object
$pr:Premium($masterMap:valuesMap)
// now have a handle to the embedded map for 'Male'
Map( $male: this["Male"] ) from $masterMap
// defining an object in which I want to populate the value from map obtained for male
$rulesResponse:RulesResponse();
then
System.out.println("rule#7 map " + $map);
// this is where in below code it is failing
$rulesResponse.abc = $innerMap.get("income");
end
when I am trying to extract the string from map against key 'income' and assign it to the 'RulesResponse' object it fails with :
[Error: unable to resolve method using strict-mode: java.lang.Object.get(java.lang.String)]
[Near : {... nse.abc = $innerMap.get("income"); ....}]
The response object is a simple POJO with getter and setter for attribute : abc
public class RulesResponse {
private String abc = "";
public String getAbc() {
return abc;
}
public void setAbc(String abc) {
this.abc = abc;
}
If I try and assign a hard coded value - it works and also reflects after the rule is executed
// this works
$rulesResponse.abc = "hard coded value";
When you get this["Male"] out of the map, it's an Object, not anything typed. It's basically due to type erasure -- Map<String, ?>.
You can get "income" out by doing Map( $income: this["income"]) from $male. Of course, now $income will too also be an Object so you'll need to cast it again. Could be as simple as a (String)$income on the right-hand side, or a $incomeStr: String() from $income on the left.
rule "Example"
when
$pr: Premium( $masterMap: valuesMap != null )
Map( $male: this["Male"] != null ) from $masterMap
Map( $income: this["income"] != null ) from $male
$rulesResponse: RulesResponse()
then
$rulesResponse.abc = (String)$income; // cast as necessary
end
We lose the nested type identity because of type erasure -- you've got a Map<String, ?> which becomes Map<String, Object> in practice.
Strongly suggest using a properly structured POJO instead of a Map as a rule input. Even if your actual code uses these nested maps (bad practice!), you should leverage a transform before calling the rules -- not only will your rules be a lot simpler and easier to work with, but they'll also be much more performant.
Even converting that inner map into an object will make things easier:
class GenderValues {
String death;
String income;
}
class Premium {
Map<String, GenderValues> valuesByGender;
}
Best practice would be to omit the Map entirely.
I'm having trouble understanding how to type promote an object's field if it is nullable. Let's say I had the following Comment class and tried to access its one nullable field:
class Comment {
final String? text;
Comment(this.text);
}
void main() {
final comment = Comment("comment");
if (comment.text!= null) {
String text = comment!.text;
}
}
The Dart compiler would give me an error for trying to assign a nullable variable to a non-nullable variable. From what I've gathered from looking into this topic, it's impossible to have type promotion with instance variables because instance variables can be modified which can then break the sound null-safety. I've seen the Null assertion operator (!.) being used in these circumstances, however it doesn't seem to work with fields, only with methods.
With dart null-safety, how should I go about assigning a nullable field such as String? to a non-nullable variable (String). To the same effect, how should I go about passing a nullable field to a function that requires a non-null argument.
You can fix it in different ways:
Use local variable (recommended)
final local = comment.text; // <-- Local variable
if (local != null) {
String text = local;
}
Use ?. and provide a default value
String text = comment?.text ?? 'Default value';
Use Bang operator !
if (comment.text != null) {
String text = comment.text!; // <-- Bang operator
}
Note: Bang operator can result in a runtime error if the text was null.
I would need to map classA fields to classB fields along with localization i.e ClassA field values needs to be converted to localized value before it mapped to classB field. Locale should be passed as an argument to mapper in order get the localized value. Is there any option to pass runtime argument to mapper along with Source and Target classes?
Thanks.
Yes, you can do this. Let's get this example from Dozer docs
BeanMappingBuilder builder = new BeanMappingBuilder() {
protected void configure() {
mapping(Bean.class, Bean.class,
TypeMappingOptions.oneWay(),
mapId("A"),
mapNull(true)
)
.exclude("excluded")
.fields("src", "dest",
copyByReference(),
collectionStrategy(true,
RelationshipType.NON_CUMULATIVE),
hintA(String.class),
hintB(Integer.class),
FieldsMappingOptions.oneWay(),
useMapId("A"),
customConverterId("id")
)
.fields("src", "dest",
customConverter("org.dozer.CustomConverter")
);
}
};
Here we can find an example of dynamically configuration definition. Take a look at this part
customConverter("org.dozer.CustomConverter")
Here you can define a custom converter using this method
FieldsMappingOption customConverter(final String type)
But it has another version
customConverter(final Class<? extends CustomConverter> type, final String parameter)
And that's your case. You can write smth like
customConverter(com.yourproject.TranslatorConverter.class, "en")
in your dynamic code base config to define a parameter for you converter. How to write an implementation of CustumConverter which apply a parameter - take a look here
I am trying to achieve attribute introduction like here but my attributes have property arguments like: [Foo(Bar = "Baz")]
How do I correctly pass the arguments? I'm not copying the attributes from something else, so I don't think I can use CustomAttributeData?
You can set properties of your custom attributes by using ObjectConstruction.NamedArguments dictionary.
For example:
public IEnumerable<AspectInstance> ProvideAspects(object targetElement)
{
Type targetType = (Type) targetElement;
var objectConstruction =
new ObjectConstruction(typeof (MyCustomAttribute).GetConstructor(Type.EmptyTypes));
objectConstruction.NamedArguments["Bar"] = "Baz";
var introduceAttributeAspect = new CustomAttributeIntroductionAspect(objectConstruction);
yield return new AspectInstance(targetType, introduceAttributeAspect);
}
Is it possible to get class of field with null value in haxe?
The function "Type.getClass" gets class of value (setted at runtime), but I need to get class defined in a compilation-time.
Function "getClassFields" returns only names of fields, without classes.
For example:
class MyCls
{
public static var i:Int = null;
public static var s:String = null;
}
trace(Type.getClass(MyCls.i)); // show "null", but I need to get Int
trace(Type.getClass(MyCls.s)); // show "null", but I need to get String
And in my situation I can't to change sources of class MyCls.
Thanks.
You can try Runtime Type Information. It's a Haxe feature which allow go get full description of a type in runtime.
http://haxe.org/manual/cr-rtti.html
Since you need to get the types for null fields, you really need to resort to Haxe's Runtime Type Information (RTTI) (as #ReallylUniqueName recomended).
import haxe.rtti.Rtti;
import haxe.rtti.CType;
class Test {
static function main()
{
if (!Rtti.hasRtti(MyCls))
throw "Please add #:rtti to class";
var rtti = Rtti.getRtti(MyCls);
for (sf in rtti.statics)
trace(sf.name, sf.type, CTypeTools.toString(sf.type));
}
}
Now, obviously, there's a catch...
RTTI requires a #:rtti metadata, but you said you cannot change the MyCls class to add it. The solution then is do add it through a macro in your build file. For instance, if you're using a .hxml file, it should then look like:
--interp
--macro addMetadata("#:rtti", "MyCls")
-main Test
With this and your own MyCls definition, the output would look like:
Test.hx:11: i,CAbstract(Int,{ length => 0 }),Int
Test.hx:11: s,CClass(String,{ length => 0 }),String