method-dispatch | 易学教程

Create a function with different arguments in R

阅读更多关于 Create a function with different arguments in R

问题 I am creating a function that does similar behavior but it would be calling different forecasting algorithms. modelBuild_auto_arima <- function(data, ...) { forecast::auto.arima(data) } modelBuild_ets <- function(data, model, ...) { forecast::ets(data, model = model) } ... Is it the best practice to keep it as separate functions and call it separately or create a generic function with "UseMethod". I tried creating with "UseMthod" modelBuild <- function(x, ...) { UseMethod("modelBuild") }

At runtime, how does Swift know which implementation to use?

阅读更多关于 At runtime, how does Swift know which implementation to use?

问题 protocol A { func f() } struct S1 : A { func f() { print("S1") } } struct S2 : A { func f() { print("S2") } } let array: [A] = [S1(), S2()] for s: A in array { s.f() } // "S1\n" "S2\n" If this was an inheritance hierarchy, I would expect Swift to use a v-table to look up the correct implementation. However, the concrete types in array could be anything that implements A , along with any number of other protocols, so how would the Swift runtime know the structure of the object if it was also

At runtime, how does Swift know which implementation to use?

阅读更多关于 At runtime, how does Swift know which implementation to use?

Itemclick event in datagrid

阅读更多关于 Itemclick event in datagrid

问题 The problem can be summarized as when clicking an item in datagrid, the text area shows the value of the item, but here the compoents are separate and hence events need to be dispatched. My mxml component file : <?xml version="1.0" encoding="utf-8"?> <mx:DataGrid xmlns:mx="http://www.adobe.com/2006/mxml" itemClick="itemClickEvent(event);" creationComplete="init()"> <mx:Metadata> [Event(name="IdSelected", type="one.IdEvent")] </mx:Metadata> <mx:Script> <![CDATA[ import genericReport.*; import

Best/most performant way to add function methods within a different function in Julia

阅读更多关于 Best/most performant way to add function methods within a different function in Julia

问题 In my problem, I have a function, say optim , that takes as one of its arguments another function, say objfunc , along with some other arguments: optim(objfunc, args...) I wish to call this function within another function, let's call it run_expt , and pass a value for objfunc that I have set to be a specific method of some other function myfunc . So specifically, say if myfunc took four arguments: myfunc(a, b, c, d) and I wanted a specific method for it to pass to optim , which fixed the

Work around Java's static method dispatching without Double Dispatch/Visitor patterns

阅读更多关于 Work around Java's static method dispatching without Double Dispatch/Visitor patterns

I am using a class Foo that provides these methods: String overloadedMethod(Object) String overloadedMethod(Goo) Since Java statically dispatches on the non-receiver argument, I cannot just pass my value (which is an Object , but might have dynamic type Goo ) and rely on the JVM to dynamically choose the "correct" method. This is my current (ugly) work-around: Object value = ...; Foo foo = new Foo(); if (value instanceof Goo) { Goo gooValue = (Goo) value; return foo.overloadedMethod(gooValue); // -> overloadedMethod(Goo) } else { return foo.overloadedMethod(value); // -> overloadedMethod

When should I use @classmethod and when def method(self)?

阅读更多关于 When should I use @classmethod and when def method(self)?

While integrating a Django app I have not used before, I found two different ways used to define functions in classes. The author seems to use them both very intentionally. The first one is one I myself use a lot: class Dummy(object): def some_function(self,*args,**kwargs): do something here self is the class instance The other one is one I do not use, mostly because I do not understand when to use it, and what for: class Dummy(object): @classmethod def some_function(cls,*args,**kwargs): do something here cls refers to what? In the Python docs the classmethod decorator is explained with this

Using -performSelector: vs. just calling the method

阅读更多关于 Using -performSelector: vs. just calling the method

I'm still kind of new to Objective-C and I'm wondering what is the difference between the following two statements? [object performSelector:@selector(doSomething)]; [object doSomething]; ennuikiller Basically performSelector allows you to dynamically determine which selector to call a selector on the given object. In other words the selector need not be determined before runtime. Thus even though these are equivalent: [anObject aMethod]; [anObject performSelector:@selector(aMethod)]; The second form allows you to do this: SEL aSelector = findTheAppropriateSelectorForTheCurrentSituation();

Java method dispatch with null argument

阅读更多关于 Java method dispatch with null argument

Why does it (apparently) make a difference whether I pass null as an argument directly, or pass an Object that I assigned the value null ? Object testVal = null; test.foo(testVal); // dispatched to foo(Object) // test.foo(null); // compilation problem -> "The method foo(String) is ambiguous" public void foo(String arg) { // More-specific System.out.println("foo(String)"); } public void foo(Object arg) { // Generic System.out.println("foo(Object)"); } In other words, why is the (commented-out) second call to foo(...) not dispatched to foo(Object) ? Update: I use Java 1.6. I could compile Hemal

Overloading is compile-time polymorphism. Really?

阅读更多关于 Overloading is compile-time polymorphism. Really?

问题 I do know the syntactical difference between overriding and overloading. And I also know that overriding is run-time polymorphism and overloading is compile-time polymorphism. But my question is: "Is overloading is really compile-time polymorphism? Is the method call really solving at compile time?". To clarify my point, let's consider an example class. public class Greeter { public void greetMe() { System.out.println("Hello"); } public void greetMe(String name) { System.out.println("Hello "