dynamic-binding

问题 I know that Objective-C uses dynamic binding for all method calls. How is this implemented? Does objective-c "turn into C code" before compilation and just use (void*) pointers for everything? 回答1: Conceptually, what is going on is that there is a dispatcher library (commonly referred to as the Objective C runtime), and the compiler converts something like this: [myObject myMethodWithArg:a andArg:b ]; into //Not exactly correct, but close enough for this objc_msgSend(myObject,

问题 I'm currently doing an assignment for one of my classes, and in it, I have to give examples, using Java syntax, of static and dynamic binding . I understand the basic concept, that static binding happens at compile time and dynamic binding happens at runtime, but I can't figure out how they actually work specifically. I found an example of static binding online that gives this example: public static void callEat(Animal animal) { System.out.println("Animal is eating"); } public static void

问题 I read the following from C++ Primer (5th edition, Section 18.1.1): "When we throw an expression, the static, compile-time type of that expression determines the type of the exception object." So I tried the following code: #include <iostream> class Base{ public: virtual void print(std::ostream& os){os << "Base\n";} }; class Derived: public Base{ public: void print(std::ostream& os){os << "Derived\n";} }; int main(){ try{ Derived d; Base &b = d; b.print(std::cout); //line 1 throw b; } catch

问题 The question is from a comment I just added to the answer to this question, but it shouldn't be a duplicate. The answer from @Bavarious to that question makes sense to me, but I am still confused why the runtime can not bind the method to the right object even the object is an id? to my understanding, dynamic binding or dynamic typing is that the compiler has no way of knowing what object behind an id, but the runtime is supposed to know that and choose the right object as the receiver of the

问题 In the following PHP code I would like to replace the __CLASS__ magic constant in the Foo class with a function __X__() (or something similar) so that when the method hello() is called from an instance $bar of the Bar class, it prints hello from Bar (instead of hello from Foo ). And I want to do this without overriding hello() inside Bar . So basically, I want a version of __CLASS__ that binds dynamically at run-time rather than at compile-time. class Foo { public function hello() { echo

问题 According to Apple's Objective C guide, methods with the same name all use the same selector and that they need to have the same return type as well as parameters. Then there is something about "static typed" methods being the exception. So is it that methods with the same name and return type + parameters that share a selector, but if it is only the same name but different return type and/or parameters, it will have a different selector - that if you sent such a message to it ... OK I don't

问题 From the docs, "If a subclass defines a static method with the same signature as a static method in the superclass, then the method in the subclass hides the one in the superclass." I understand the difference between method hiding and overriding. However, it's strange to say that the subclass hides the superclass method because if you have the following: public class Cat extends Animal { public static void testClassMethod() { System.out.println("The static method in Cat"); } public void

问题 The documentation for Clojure with-local-vars and with-bindings doesn't suffice for me to distinguish the two. Any hints? 回答1: New var s are temporarily created by with-local-vars . Existing var s are temporarily rebound by with-bindings . In both cases the bindings are thread-local. Note that with-bindings is, as far as I can tell, primarily useful as a helper to pass bindings from another context by using a map returned by get-thread-bindings . The similar function binding would be more

问题 I created a function that returns a function in Elisp: (defun singleton-set (elem) (defun f (n) (= n elem)) f) I try to run this in IELM, and it fails: ELISP> (singleton-set 5) *** Eval error *** Symbol's value as variable is void: f ELISP> ((singleton-set 5) 5) *** Eval error *** Invalid function: (singleton-set 5) Due to What is the difference between Lisp-1 and Lisp-2? i changed the code to (defun singleton-set (elem) (defun f (n) (= n elem)) #'f) And invocation to (funcall (singleton-set

问题 I have found an issue about static binding. My real class are very extended, so I will use several toy class to express my problem. We suppose that we have the following hierarchy. public class Element{} public class Element1 extends Element{} public class Element2 extends Element{} I have a Stock class which use the different Element specialization defined by Element hierarchy. public class Stock{ public void operation(Element1 e1){ System.out.println("Operation - " + e1.getClass().getName()