I've read some documentation and downloaded samples but I still got a question.
In most sample, the GIN module uses something like :
bind(MainActivityMapper.class);
bind(VerticalMasterActivityMapper.class);
I don't understand what it does? If I remove it from the sample code, everything works perfectly.
Thanks for any answer.
Someone pointed me to the GUICE page : http://google-guice.googlecode.com/git/javadoc/com/google/inject/Binder.html
There is no reason for it to be different in Gin.
Here is what it says for this particular case :
This statement does essentially nothing; it "binds the
class to itself" and does not change Guice's default behavior. You may
still want to use this if you prefer your Module class to serve as an
explicit manifest for the services it provides. Also, in rare cases,
Guice may be unable to validate a binding at injector creation time
unless it is given explicitly.
Note: I'm not sure wether or not I should Accept my own answer, so I'll leave it as is.
Related
I have a use case where I need to create a class based on user input.
For example, the user input could be : "(Int,fieldname1) : (String,fieldname2) : .. etc"
Then a class has to be created as follows at runtime
Class Some
{
Int fieldname1
String fieldname2
..so..on..
}
Is this something that Scala supports? Any help is really appreciated.
Your scenario doesn't seem to make sense. It's not so much an issue of runtime instantiation (the JVM can certainly do this with reflection). Really, what you're asking is to dynamically generate a class, which is only useful if your code makes use of it later on. But how can your code make use of it later on if you don't know what it looks like? For example, how would your later code know which fields it could reference?
No, not really.
The idea of a class is to define a type that can be checked at compile time. You see, creating it at runtime would somewhat contradict that.
You might want to store the user input in a different way, e.g. a map.
What are you trying to achieve by creating a class at runtime?
I think this makes sense, as long as you are using your "data model" in a generic manner.
Will this approach work here? Depends.
If your data coming from a file that is read at runtime but available at compile time, then you're in luck and type-safety will be maintained. In fact, you will have two options.
Split your project into two:
In the first run, read the file and write the new source
programmatically (as Strings, or better, with Treehugger).
In the second run, compile your generated class with the rest of your project and use it normally.
If #1 is too "manual", then use Macro Annotations. The idea here is that the main sub-project's compile time follows the macro sub-project's runtime. Therefore, if we provide the main sub-project with an "empty" class, members can be added to it dynamically at compile time using data that the macro sees at runtime. - To get started, Modify the macro to read from a file in this example
Else, if you're data are truly only knowable at runtime, then #Rob Starling's suggestion may work for you as it did me. I'll share my attempt if you want to be a guinea pig. For debugging, I've got an App.scala in there that shows how to pass strings to a runtime class generator and access it at runtime with Java reflection, even define a Scala type alias with it. So the question is, will your new dynamic class serve as a type-parameter in Slick, or fail to, as it sometimes does with other libraries?
What we want is basically this:
/foo/* controllers.FooController.foo
However this doesn't work.
We have found the following workaround:
/foo/*ignore controllers.FooController.foo(ignore)
But this makes the code of the method controllers.FooController.foo slightly ugly. Is there a better way to do this?
Looking at the code over here, the router isn't able to deal with the "slug" part without specifying an identifier... the parser combinator doesn't declare it as optional, and the map (^^) is clearly using it as is.
It could be a good feature request if it wouldn't induce other problems where a pattern will hide all other routes because it's defined higher in the file (or even worst, included).
And it looks like it has been done on purpose if we look here, we can figure out that dynamic parameter cannot be assigned a default value -- indeed, in this case we'll fall in the case I've just mentioned :-/.
My first advice would be to tell you to use ignore as an Option[String] and the action definition to set it as None (rather than an empty String because it's more expressive).
My second would be to incite you to wonder if such case is really relevant, because it's error prone and could hide further problems
I tried searching on google, and got literally no results when trying to figure out what this means. My console is logging:
objc[17048]: Class _NSZombie_GEOLatLng is implemented in both ?? and ??. One of the two will be used. Which one is undefined.
objc[17048]: Class _NSZombie_GEOLatLng is implemented in both ?? and ??. One of the two will be used. Which one is undefined.
objc[17048]: Class _NSZombie_GEOLocation is implemented in both ?? and ??. One of the two will be used. Which one is undefined.
objc[17048]: Class _NSZombie_GEOLocation is implemented in both ?? and ??. One of the two will be used. Which one is undefined.
Anyone seen this before, or have any idea what it means, what's causing it, and if it's a problem?
I've seen it. Specifically, on OS X - but the cause should be the same. GEOLocation (and others) is defined in two images which are loaded into the process.
If that were a class you wrote, the class' symbols are defined in multiple object files (would likely be a linker error though…), in the linked libraries, loaded bundles, or some combination of - when code may be loaded dynamically.
If it's not a class you wrote (or synthesized), file a bug with the creator of the class.
It's also possible that the class is defined in your app, and also defined in a linked library. In that event, you would need to change the name of your class.
It is definitely a problem. The class (with that name) is being loaded into the objc runtime twice, and there are no guarantees as to which implementation will be returned when an instance is created since objc uses a flat namespace.
In this case, the class exists in the system frameworks so... send it to the bug reporter - it deserves be fixed quickly.
This is a harmless warning that occurs when you have enabled zombie warnings in the build scheme. You can ignore it.
I had this obscure message and noticed that a NIB had been removed from the project, but code was still using it. You may want to check if any resources have been removed from the bundle that are still in use.
(I am also using .NET 4.0 and VS 2010.)
I created a function import returning a complex type, as explained at http://msdn.microsoft.com/en-us/library/bb896231.aspx. The function import and new complex type appear in my .edmx file and in the Designer.cs file. However, the function does not appear when I view the service in the browser, and when I add or update a service reference in the client project, the function does not appear there either - as is to be expected, given the first result.
Creating an imported function and using it seems conceptually very simple and straightforward, and one would think it would just work, as Microsoft's step-by-step instructions appear to suggest: http://msdn.microsoft.com/en-us/library/cc716672.aspx#Y798 (which article shows the SP returning entity types - I tried this also, and it doesn't work for me either).
This blog post shows the addition of a method to the DataService class, which Microsoft's instructions omit: http://www.codegain.com/articles/wcf/miscellaneous/how-to-use-stored-procedure-in-wcf-data-service.aspx I tried adding one method returning a list of entity types and another returning a list of complex types, and still had no success. I still could not access the functions, either directly via the browser or from the client application via a service reference.
Thanks in advance for any help with this.
config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
MS would do well to add a note to the walkthroughs stating that the above bit of code must be there. (It may be better to enable each operation explicitly than to use "*".)
http://www.codegain.com/articles/wcf/miscellaneous/how-to-use-stored-procedure-in-wcf-data-service.aspx shows that line of code. Also, something it is there in the code, commented out, when one creates the WCF Data Service. Some of us like to delete commented-out code that we aren't using and that seems irrelevant - perhaps doing so a bit prematurely, sometimes.
...and why has the package this misleading name (I assumed it had something to do with JavaME or mobile/smart phones)?
I found no references on the internet about scala.mobile.Code or scala.mobile.Location at all nor did I manage to do anything with those classes except getting ClassCastExcetions or NoSuchMethodErrors.
Actually there is not even a single test against scala.mobile in the Scala's test tree which could help understanding that code.
The classes really smell like they were forgotten in the source tree a long time ago and got accidentally released since that.
Maybe I just missed something about them?
Update:
scala.mobile was removed in Scala 2.9.
I just checked the source code.
When Scala changed the name mangling of class files a few years ago and it seems people forgot to update these classes accordingly.
So my answer would be:
At least Location has no purpose, because it is not possible to get anything sensible out of it (except exceptions) and Code without Location is severely limited. It works though if you pass the class literal to Code directly:
import scala.mobile._
val c = new Code(classOf[scala.collection.mutable.StringBuilder])
c.apply[StringBuilder, String]("append")("Foo")
c.apply[String]("toString")() // returns "Foo"
c.apply[Int]("length")() // returns 3
Looks like yet-another implementation in the standard library of reflection-slightly-nicer.
The description of Location pretty much explains what that is about:
The class Location provides a create method to instantiate objects
from a network location by specifying the URL address of the jar/class file.
It might be used by remote actors. Maybe.
As for why it has this misleading name? Well, back in 2004 smart phones had really low penetration, so maybe the association wasn't all that strong.