I have a function that handles two types: NVector and NMatrix; the former is derived from the latter. This function is basically a specialized copy constructor. I want it to return an object of the same type as that upon which it was called, so, NVector returns NVector, not NMatrix.
static VALUE nm_init_modifiedcopy(VALUE self) {
// ... some code ...
// formerly, I had cNMatrix where klass is. But it could also be cNVector!
return Data_Wrap_Struct(klass, mark_func, delete_func, unwrapped_self_copy);
}
How do I get the class property of an object to pass into Data_Wrap_Struct?
Like clockwork, as soon as I ask a question on Stackoverflow, I find the answer.
The macro is CLASS_OF.
static VALUE nm_init_modifiedcopy(VALUE self) {
// ... some code ...
return Data_Wrap_Struct(CLASS_OF(self), mark_func, delete_func, unwrapped_self_copy);
}
Related
I've recently taken upon myself to add setter and getter methods to my class.
Since doing this, many parts of my code got broken and I'm unable to access getter methods.
Take the example below:
private loadInputs() : Input[] {
var inputs = <Input[]>this.get('inputs');
inputs.sort((a,b) => a.QuoteRef().localeCompare(b.QuoteRef()))
return( inputs || [] );
}
My input class has 2 variables,
_Project: string
_line: string
Which I access using a method QuoteRef()
public QuoteRef(): string {
return this._Project.concat('-' + this._Line.toString().padStart(3,'0'));
}
Whenever I try to access a method or a getter from my class on an item that is casted as an Input, I can see the variables (though not access them as they are private), but the prototype section doesn't contain any of the methods.
This triggers the following error in the website console:
TypeError: a.QuoteRef is not a function
What am I doing wrong?
Update
I got it to work by updating the code as follows:
inputs.sort((a,b) => {
let first = new Input(a);
let second = new Input(b);
return first.QuoteRef().localeCompare(second.QuoteRef());
});
Without seeing your complete class I can only guess, but I think that a and b in your sort are not of the type you expect. I can't see what this.get('inputs') does, but I suspect it is not returning an array with Input class objects. Hence the function cannot be found (is not a function). You could try:
inputs.sort((a,b) => {
console.log(typeof a);
console.log(typeof b);
a.QuoteRef().localeCompare(b.QuoteRef());
})
and check what the type is. Then check what your this.get actually returns.
Edit: forgot to mention that your IDE probably does not warn you because you cast the output of this.get to <Input[]>.
I am attempting to implement a solution from How to set canBecomeKeyWindow? Into my native C application using Objective-C runtime (The app is already written with objective C Runtime). Is there a way to create a subclass purely in Objective-C Runtime?
Right now I just create NSWindow object but need to be able to create my own so I can override the function specified in that question.
objc_msgSend((id)objc_getClass("NSWindow"), sel_registerName("alloc"));
The signature of can_become_key_window_true is slightly incorrect. According to the documentation (https://developer.apple.com/documentation/objectivec/objective-c_runtime/imp?language=objc) the function should have at least two arguments: "self" and "_cmd". So the signature should be like:
static bool can_become_key_window_true(__unused id _self, __unused SEL _cmd) {
return true;
}
You could also use #encode to construct the type encoding for the function.
char encoding[10]; // should be enough
snprintf(encoding, 10, "%s%s%s", #encode(BOOL), #encode(id), #encode(SEL));
... or you could get a method from UIWindow and get its type encoding like:
Method m = class_getInstanceMethod(objc_lookUpClass("UIWindow"), sel_getUid("canBecomeKeyWindow"));
const char *encoding = method_getTypeEncoding(m);
And as you might have noticed you could use sel_getUid() instead of sel_registerName as you expect this selector to be already registered by this time (because you are about to override an existing method).
To allocate a new instance you could use
window = class_createInstance(__UIWindow);
Figured it out after a lot of code searching:
// Subclass NSWindow with overridden function
Class __NSWindow =
objc_allocateClassPair(objc_getClass("NSWindow"), "__NSWindow", 0);
class_addMethod(__NSWindow,
sel_registerName("canBecomeKeyWindow"),
(IMP)can_become_key_window_true, "B#:");
objc_registerClassPair(__NSWindow);
// Allocate a new __NSWindow
window = objc_msgSend((id)__NSWindow, sel_registerName("alloc"));
And then can_become_key_window_true is defined as:
static bool can_become_key_window_true() {
return true;
}
I use objc_allocateClassPair to subclass the object and return a Class of that object. Then I use class_addMethod to override the method canBecomeKeyWindow. And finally use objc_registerClassPair to register my new class before using it as I would a normal NSWindow.
there is my program：
static class Vprog extends AbstractFunction3< Object, OddRange, OddRange, OddRange> implements Serializable {
#Override
public OddRange apply(Object l, OddRange self, OddRange sumOdd) {
System.out.println(self.getS()+self.getI()+" ---> "+sumOdd.getS()+sumOdd.getI());
self.setS(sumOdd.getS() + self.getS());
self.setI(self.getI() + sumOdd.getI());
return new OddRange(self.getS(), self.getI());
}
}
the question is if I use return new OddRange like above in class Vprog，I can change the vertexRDD
But, if I use retuen self, like:
static class Vprog extends AbstractFunction3< Object, OddRange, OddRange, OddRange> implements Serializable {
#Override
public OddRange apply(Object l, OddRange self, OddRange sumOdd) {
System.out.println(self.getS()+self.getI()+" ---> "+sumOdd.getS()+sumOdd.getI());
self.setS(sumOdd.getS() + self.getS());
self.setI(self.getI() + sumOdd.getI());
return self;
}
}
The vertexRDD didn't change.
I know RDD is immutable, but how can I update the vectexRDD in spark.graphx.pregel correctly？Can you give me any advise？
I have found the same question:
Spark Pregel is not working with Java
But I use spark 2.3.0,maybe it have the same problem?
I think I have found the answer:
We must return a new one, if we wanna change the data which will be used in next sendMsg in Vprog.
that's because Vprog changes the vertexRDD, but sendMsg uses the tripletsRDD. And what's more, the verteies in the tripletsRDD are not equels to vertexRDD, it's just a copy of vertexRDD. So，the problem is when to update the verteies in tripletsRDD when vertexRDD is changed.
We can follow the source below to find out the reason：
first part：pregel(in Pregel.scala)->joinVertices（in GraphOps.scala）->outerJoinVertices(in GraphImpl.scala)->diff(in VertexRddImpl.scala)
And then:
second part：pregel(in Pregel.scala)->mapReduceTriplets(in GraphXUtils.scala)->aggregateMessagesWithActiveSet(in GraphImpl.scala).
In first part, I found that Vprog will compare the VertexRDD data before and after execution. SO, if it is modified on the source data, they will be the same. Then a data structure named replicatedVertexView will be generated to store different VertexRDD info. If they are same, nothing will be stored.
In second part, it will update the tripletsRDD with the infomations which stored in the relicatedVertexView. And then, use the tripletsRDD in sendMsg.
So, if we don't return new in Vprog, the tripletsRDD will not be changed with VertexRDD, and the results will be wrong.
I created some classes with Ruby's C API. I want to create a function whose behavior will change depending on the class of the Ruby object.
I tried to use is_a? from Ruby, however, I don't think it's the good way to do this. I checked "Creating Extension Libraries for Ruby" without success. The only direct way to check classes is with the default types.
I have my class "Klass" already created:
VALUE rb_cKlass = rb_define_class("Klass", rb_cObject);
And how I wanted to check if the class is the good one:
VALUE my_function(VALUE self, VALUE my_argument) {
if(rb_check_class(my_argument), rb_cKlass)) {
// do something if my_argument is an instance of Klass
} else {
return Qnil;
}
}
Is there a way to do this?
I came across this recently, and used the RBASIC_CLASS macro, but was getting segfaults in certain scenarios for some unexplained reason.
After scanning through ruby.h, I found the CLASS_OF macro, which returns the class as VALUE of a given object.
VALUE obj = INT2NUM(10);
VALUE klass = CLASS_OF(obj); // rb_cInteger
Using Ruby 2.5
Every ruby object is internally represented by RObject struct (I will copy the source here for the sake of future readers):
struct RObject {
struct RBasic basic;
union {
struct {
uint32_t numiv;
VALUE *ivptr;
void *iv_index_tbl; /* shortcut for RCLASS_IV_INDEX_TBL(rb_obj_class(obj)) */
} heap;
VALUE ary[ROBJECT_EMBED_LEN_MAX];
} as;
};
The very first member, RBasic, defines the class:
struct RBasic {
VALUE flags;
const VALUE klass;
}
To get an access to RBasic metadata of anything, one might use RBASIC macro:
RBASIC(my_argument)
To get the class directly, one might use RBASIC_CLASS macro:
RBASIC_CLASS(my_argument)
If you want to stay close to the is_a? Ruby fashion (i.e. check if any of the ancestors is the expected class), you could directly use the C implementation of is_a?, rb_obj_is_kind_of:
rb_obj_is_kind_of(my_argument, rb_cKlass) // Qtrue OR Qfalse
And since Qfalse == 0, you can just use that method as a condition:
VALUE my_function(VALUE self, VALUE my_argument) {
if(rb_obj_is_kind_of(my_argument, rb_cKlass)) {
// do something if my_argument is an instance of Klass
} else {
return Qnil;
}
}
To find this method, just check Object#is_a? documentation and click to toggle source, you'll see the C implementation if it is a C function (hence this will work for most of the standard lib).
How do you define a static extension method in Kotlin? Is this even possible? I currently have an extension method as shown below.
public fun Uber.doMagic(context: Context) {
// ...
}
The above extension can be invoked on an instance.
uberInstance.doMagic(context) // Instance method
but how do I make it static method like shown below.
Uber.doMagic(context) // Static or class method
To achieve Uber.doMagic(context), you can write an extension to the companion object of Uber (the companion object declaration is required):
class Uber {
companion object {}
}
fun Uber.Companion.doMagic(context: Context) { }
This is what the official documentation says:
Kotlin generates static methods for package-level functions. Kotlin
can also generate static methods for functions defined in named
objects or companion objects if you annotate those functions as
#JvmStatic. For example:
Kotlin static methods
class C {
companion object {
#JvmStatic fun foo() {}
fun bar() {}
}
}
Now, foo() is static in Java, while bar() is not:
C.foo(); // works fine
C.bar(); // error: not a static method
I actually had this exact question 30 minutes ago, so I started digging around and couldn't find any solution or workaround for this, BUT while searching I found this section on the Kotlinglang website that states that:
Note that extensions can be defined with a nullable receiver type. Such extensions can be called on an object variable even if its value is null.
So then I had the craziest idea ever, why not define an extension function with a nullable receiver (without actually using that receiver) and then call it on a null object!
So I tried that, and it worked pretty well, but it looked so ugly. It was like this:
(null as Type?).staticFunction(param1, param2)
So I went around that by creating a val in my extensions file of the receiver type that had a value of null and then use it in my other class.
So, as an example, here is how I implemented a "static" extension function for the Navigation class in Android:
In my NavigationExtensions.kt file:
val SNavigation: Navigation? = null
fun Navigation?.createNavigateOnClickListener(#IdRes resId: Int, args: Bundle? = null, navOptions: NavOptions? = null,
navigationExtras: Navigator.Extras? = null) : (View) -> Unit {
//This is just implementation details, don't worry too much about them, just focus on the Navigation? part in the method declaration
return { view: View -> view.navigate(resId, args, navOptions, navigationExtras) }
}
In the code that uses it:
SNavigation.createNavigateOnClickListener(R.id.action_gameWonFragment_to_gameFragment)
Obviously, this isn't a class name, it is just a variable of the class type that has a null value. This is obviously ugly on the extension maker side (because they have to create the variable) and on the developer side (because they have to use the SType format instead of the actual class name), but it is the closest that can be achieved right now compared to actual static functions. Hopefully, the Kotlin language makers will respond to the issue that was created and add that feature in the language.
Since I keep coming across this when searching, here's a different approach I haven't seen anyone mention that works in a static way and it works with generics!
Extension definitions:
// Extension function
fun <T> KClass<T>.doSomething() = /* do something */
// Extension Property
val <T> KClass<T>.someVal get() = /* something */
Usage:
MyType::class.doSomething()
MyType::class.someVal
As you can see, the trick is attaching the extension function to the KClass of the type instead since that can be referenced statically.
You can create a static method with using Companion object like:
class Foo {
// ...
companion object {
public fun bar() {
// do anything
}
}
}
and then you can call it like:
class Baz {
// ...
private fun callBar() {
Foo.bar()
}
}
Recomend you to look at this link. As you can see there, you just should declare method at the top-level of the package (file):
package strings
public fun joinToString(...): String { ... }
This is equal to
package strings;
public class JoinKt {
public static String joinToString(...) { ... }
}
With constans everything are the same. This declaration
val UNIX_LINE_SEPARATOR = "\n"
is equal to
public static final String UNIX_LINE_SEPARATOR = "\n";
I also required the ability to extend a Java object with a static method and found the best solution for me was to create a Kotlin object that extended the Java class and add my method there.
object Colour: Color(){
fun parseColor(r: Int?, g: Int?, b: Int?) = parseColor(String.format("#%02x%02x%02x", r, g, b))
}
invocation:
val colour = Colour.parseColor(62, 0, 100)
I'm also quite fond of having the possibility to add static extension methods in Kotlin. As a workaround for now I'm adding the exntension method to multiple classes instead of using one static extension method in all of them.
class Util
fun Util.isDeviceOnline(context: Context): Boolean {
val connMgr = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
val networkInfo = connMgr.activeNetworkInfo
return networkInfo != null && networkInfo.isConnected
}
fun Activity.isDeviceOnline(context: Context) = { Util().isDeviceOnline(context) }
fun OkHttpClient.isDeviceOnline(context: Context) = { Util().isDeviceOnline(context) }
To create an extension method in kotlin you have to create a kotlin file(not a class) then declare your method in the file
Eg:
public fun String.toLowercase(){
// **this** is the string object
}
Import the function in the class or file you are working on and use it.