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  1. #include <iostream>
  2. #include <functional>
  3. #include <unordered_map>
  4. #include <vector>
  5. #include <memory>
  6.  
  7. // Gemeinsame Basisklasse
  8. class Base {
  9.   public:
  10.   	// Virtueller Destruktor
  11.   	virtual ~Base () {}
  12.     virtual void test () = 0;
  13. };
  14. // Abgeleitete Klassen
  15. class Derived1 : public Base {
  16.   public:
  17.   	virtual ~Derived1 () { std::cout << "Derived1::~Derived1\n"; }
  18.     virtual void test () { std::cout << "Derived1::test\n"; }
  19. };
  20. class Derived2 : public Base {
  21.   public:
  22.   	virtual ~Derived2 () { std::cout << "Derived2::~Derived2\n"; }
  23.     virtual void test () { std::cout << "Derived2::test\n"; }
  24. };
  25.  
  26. // Zuordnung (map) ID->Factory-Funktion
  27. std::unordered_map<int, std::function<std::unique_ptr<Base> ()>> factories {
  28. 	{ 1 , []() { return std::unique_ptr<Base> (new Derived1); }},
  29. 	{ 42, []() { return std::unique_ptr<Base> (new Derived2); }}};
  30.  
  31. std::vector<std::unique_ptr<Base>> getObjects (std::vector<int> input) {
  32. 	// Erzeugte Objekte
  33. 	std::vector<std::unique_ptr<Base>> objects;
  34.  
  35. 	for (int i : input) {
  36. 		// Suche Factory-Funktion...
  37. 		auto f = factories.find (i);
  38. 		if (f != factories.end ())
  39. 			// Rufe Factory-Funktion auf, erstelle Objekt, speichere in "objects"
  40. 			objects.push_back ((f->second) ());
  41. 		else
  42. 			std::cout << "Unbekannte ID " << i << std::endl;
  43. 	}
  44. 	return objects;
  45. }
  46.  
  47.  
  48. int main () {
  49. 	// Angenommen, das hier ist zur kompilezeit nicht bekannt (Dateieingabe o.ä.); enthält Liste an ID's, von denen Objekte angelegt werden sollen
  50. 	std::vector<int> input { 42, 1, 1, 42, 3, 1 };
  51. 	auto objects = getObjects (std::move (input));
  52.  
  53. 	// Rufe virtuelle Funktion auf Objekten auf
  54. 	for (auto& obj : objects)
  55. 		obj->test ();
  56.  
  57. 	// unique_ptr löscht Objekte hier
  58. }
  59.  
  60.  
Success #stdin #stdout 0s 3480KB
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Standard input is empty
stdout
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Unbekannte ID 3
Derived2::test
Derived1::test
Derived1::test
Derived2::test
Derived1::test
Derived2::~Derived2
Derived1::~Derived1
Derived1::~Derived1
Derived2::~Derived2
Derived1::~Derived1
https://ideone.com/h2xEbm
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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