Kotlin
My problem is that when I trying to make a query from the database in the Dao annotation interface, the query does not perceive the value, it only sees String
How I can fix this?
implementations:
implementation 'androidx.room:room-ktx:2.5.0'
kapt 'androidx.room:room-compiler:2.5.0'
in plugins I added:
id 'kotlin-kapt'
My code
I try to update all implementations in project it's don't work
Related
I am very new to Kotlin development and I came across custom annotation classes in the documentation.
Is there a way for me to use an annotation on a function as a way to pre-populate some variables, or to run a decorator function before running the annotated function?
Something like:
class TestClass {
#Friendly("Hello World")
private fun testFun() {
greet()
//does something else
}
}
with an annotation class like
#Target(AnnotationTarget.FUNCTION)
#Retention(AnnotationRetention.BINARY)
annotation class Friendly(val message: String) {
fun greet() {
println(message)
}
}
I know this isn't valid Kotlin code, but I can't find any examples on how to actually use values from annotations without using reflection (if it's even possible)
Please let me know if I can do something like this, and more usefully, a better resource on annotation classes for Kotlin?
To make use of your custom annotations, you need to either create your own annotation processor (and use kapt Kotlin compiler plugin) to generate some new sources (but not modify existing!) at compile time, or use #Retention(AnnotationRetention.RUNTIME) meta-annotation (which is default in Kotlin), so that they could be accessed via reflection in runtime.
#Retention(AnnotationRetention.BINARY) meta-annotation you're using is equivalent of #Retention(RetentionPolicy.CLASS) in java, which is mostly useless (see https://stackoverflow.com/a/5971247/13968673).
What you're trying to do with annotations (call some additional code before/after method execution) reminds me aspect-oriented programming. Take a look at Spring AOP and AspectJ frameworks, following this paradigm, and their approach for annotations processing. TL;DR: Spring AOP is processing annotations in runtime, generating proxy-classes with respectful code, while AspectJ is using its own compiler (even not an annotation processor, cause it also introduces its own syntactic extension for java language), and can generate respectful bytecode at compile-time. They both are originally java-oriented, but with some configurational pain could be used with Kotlin too.
I am using mvvm architecture and injecting the repository in the viewmodel using hilt. There is a variable in the activity (i am getting the variable in the activity through an intent) which i need to pass to the viewmodel and i thought viewmodel factories might help. But how to use it alongside hilt?
I am not aware of hilt implementing any sort of "assisted injection" for viewmodels, like the assisted injection library from square. But you can easily manage dynamic data within your viewmodel using this sample from this google sample.
fun setLogin(login: String?) {
if (_login.value != login) {
_login.value = login
}
}
with this code you will only update the livedata if the value is null, thus even if the fragment rotates, the data will remain the same.
If you wanna check a slight outdated assisted injection project, I have this one in Kotlin.
Data classes print out just fine in MPP projects. When I toString() the KClass object for my class, I get:
class com.example.MySimpleClass (Kotlin reflection is not available)
How Can I do what data class does and have a nice clean name without reflection?
I don't have it set up myself to test, so answer is based purely on documentation:
KClass.simpleName is available in Common code; qualifiedName isn't, but since 1.3 it is on every platform, so you could define an expect fun in your multiplatform part and make all actual implementations access qualifiedName.
I'd like to write a plugin for Intellij IDEA that should modify a Java and Kotlin code.
I use the method
PsiClass.getMethods()
in order to get all methods of Java and Kotlin classes. So far so good, so then I use methods like
PsiClass.add(), PsiClass.addAfter(), PsiClass.addBefore()
that all work fine once they are called on Java files, but start to throw an exception
IncorrectOperationException
once I called them on a Kotlin class.
I'd appreciate any hint on how I can modify Kotlin and Java classes (preferably using the same approach).
When you search for a Kotlin class via the JavaPsiFacade, it returns the light class which is a shallow representation that is just based on the information in the class file. In order to add PSI elements, you have to call navigationElement on it. Then, IJ will parse the source and build a full PSI tree that can be modified.
However, if the class is a Kotlin class, navigationElement will return a KtClass which is not derived from PsiClass. You will have to use the facilities in the Kotlin hierarchy to modify it. Method instances in Kotlin are also not instances of PsiMethod, but instances of KtMethod.
For analyzing Java and Kotlin sources in a common fashion there is a different syntax tree called "UAST", but for modifications you need a language-specific approach.
My application has this structure: there's a RepositoryFacade (that is a Singleton) that uses many other ObjectRepository that are Singleton (UserRepository, etc).
Now I'd like to test it, mocking the [Objetct]Repositiries. To do that I made the [Objetct]Repositiry implements an interface, and then i tried to:
final IUserRepository mockIUserRepository= context.mock(IUserRepository.class);
RepositoryFacade.getInstance().setUserRepository(mockIUserRepository);
final User testUser = new User("username");
// expectations
context.checking(new Expectations() {{
oneOf (mockIUserRepository).save(testUser);
}});
// execute
RepositoryFacade.getInstance().save(testUser);
And in RepositoryFacade I added:
public IUserRepository userRepository = UserRepository.getInstance();
But if I try to run the test, I obtain:
java.lang.SecurityException: class "org.hamcrest.TypeSafeMatcher"'s signer
information does not match signer information of other classes in the same
package
p.s. Originally my RepositoryFacade had not a IUserRepository variable, I used it asking always UserRepository.getInstance().what_i_want(). I introduced it to try to use JMock, so if not needed I'll be glad to remove that bad use of Singleton.
Thanks,
Andrea
The error you're getting suggests that you have a classloading issue with the org.hamcrest package rather than any issue with your singletons. See this question for more on this exception and this one for the particular problem with hamcrest and potential solutions.
Check your classpath to make sure you're not including conflicting hamcrest code from multiple jars. If you find hamcrest in multiple jars, this may be corrected by something as simple as changing their order in your classpath.
Junit itself comes in two versions - one may include an old version of hamcrest. Switching to the one not including hamcrest may also fix your problem.
If you can find a way to do it, it would be better in the long run to get rid of the singletons altogether and instead do dependency injection using something like Spring or Guice.
But what you're doing should work, once you deal with the classloading, and it's a reasonable approach to dealing with singletons in a testing context.