Is it possible in J2ME to call/invoke a method by its name.just like we have getDeclaredMethod in java .
The java.lang.reflect package is available only in CDC 1.1.2. If you're not on such configuration, you're out of luck. There is no way to invoke a method by name without reflection.
A workaround would be to create a map from strings (method names) to appropriate classes on which you can invoke the methods.
Closest you can get is to instantiate a class by name using Class.forName("com.class.ClassName").newInstance() -- that will execute a parameterless constructor.
Related
I'm learning android studio 4.1 using Kotlin from a 2020 book. In one of the examples they are using a MutableLiveData object. When I try to use code completion with this line:
result.setValue(value.toFloat()*usd_to_eu_rate)
the only option is the setter result.value tough result.setValue does work just fine. So I was wondering what the difference is between the two and why value does not show up in code compleation.
Thanks to this link - kotlinlang.org/docs/reference/java-interop.html#getters-and-setters - provided by #IR42 and other information by other contributors whos comments were unfortunately deleted I found my answer:
MutableLiveData is a Java class and Kotlin will infer a property when the Java class has methods that follow the Java conventions for getters and setters (no-argument methods with names starting with get and single-argument methods with names starting with set)
Code completion will not suggest the Java getter methods (i.e. getValue and setValue) but it will suggest the Kotlin inferred property (i.e. value)
You can still use the Java getter/setter methods but this is discouraged.
I'm trying to use AutoMapper in a API wrapper class library project to map from API models to our domain models. While looking at the AutoMapper documentation I ran into the inline mapping feature.
Documentation says:
AutoMapper creates type maps on the fly (new in 6.2.0). When you call Mapper.Map for the first time, AutoMapper will create the type map configuration and compile the mapping plan. Subsequent mapping calls will use the compiled map.
So I wrote the following line of code in my wrapper class library:
var data = response.Results.Select(Mapper.Map<Session, Media>).ToList();
basically just trying to map the Session object I get from the API into our Media objects. But this throws the following error:
Mapper not initialized. Call Initialize with appropriate configuration. If you are trying to use mapper instances through a container or otherwise, make sure you do not have any calls to the static Mapper.Map methods, and if you're using ProjectTo or UseAsDataSource extension methods, make sure you pass in the appropriate IConfigurationProvider instance.
I was under the impression that inline mapping is exactly supposed to bypass having to initialize and define configuration for AutoMapper? Am I wrong?
Also if I am indeed wrong then how are you supposed to configure and initialize AutoMapper inside a class library to where it happens only once? I would like the library to be independent, meaning I don't want the programmer using the library to have to configure AutoMapper in his project in order for the library to work properly.
I have a question that keeps bothering me. Currently, I have started using Kohana 3.2 Framework. I've written a helper to handle some functionality - I have a number of methods, which are (as it should be) declared STATIC. But, all of these methods are somehow working with the database, so I need to load a model. Currently, every method has a non-static variable like this:
$comment = new Model_Comments;
$comment->addComment("abc");
OK, it seems to be working, but then I wanted to get rid of this redundancy by using class attribute to hold the instance of the model (with is class as well).
Something like this:
private static $comment; // Declaring attribute
self::$comment = new Model_Comment; // This is done within helper __constuct method
self::$comment->addComment("abc"); // And call it within the method.
But, I got failed with: Call to a member function addComment() on a non-object
Question is: is it possible to do it ? Maybe there are some other approaches ?
Sorry for a long story and, thanks in advice! :P
A static method cannot call a non-static method without operating on an instance of the class. So, what you're proposing won't work. There may be a way do accomplish something similar, but what about trying the following:
You could implement the singleton or factory pattern for your "helper" class. Then, you could create the model (as an attribute) as you instantiate/return the instance. With an actual instance of your "helper" class, you won't have to worry about the static scope issues.
In other words, you can create a helper-like class as a "normal" class in your application that, upon creation, always has the necessary model available.
I'd be happy to help further if this approach makes sense.
David
How can we add some common constraints (i.e. maxLength, nullable) to a property of a Groovy class? I know we can do it at Grails domain class, but is it possible if that is a Groovy class (I use it as a DTO class for my Grails project)?
Thank you so much!
You can add constraints to command classes. If a command class is in the same .groovy file as a controller (in Groovy you can have more than one public class in each .groovy file), you don't need to do anything special for Grails to recongise it as a command class.
However, if your command class is somewhere else (e.g. under src/groovy), you need to annotate it with #Validateable and add the package name to the grails.validateable.packages parameter in Config.groovy. Here's an example of a command that's not in the same file as a controller
pacakge com.example.command
#Validateable
class Person {
Integer age
String name
static constraints = {
name(blank: false)
age(size 0..100)
}
}
Add the following to Config.groovy
grails.validateable.packages = ['com.example.command']
Command classes have a validate() method added by Grails. After this method is called, any errors will be available in the errors property (as per domain classes).
Using a grails Command Object is probably your best bet. It has constraints and validation, but no database backing. It's normally a value object that controllers use, but you could instantiate one outside of a controller without any problems.
Not sure if this is relevant to your use (I am not familiar with DTOs), but in the current version (2.3.8), you can also add Grails constraints to an abstract class, and they will be inherited by the domains that extend it. Your IDE might not like it though ;)
I have a method void abc(IAnimal animal). When I type in another method abc( how do I make ReSharper show a list of objects implementing IAnimal?
Thx
On my installation CTRL-ALT-B gives you a list of implementations of an interface.