C++ Template Example

Templates can be viewed as a form of static compile time virtualization. Was that a mouthful or what?!? Here is a template example that highlights template specialization and default template parameters that can be over-riden by a class. Remember to always have your template definitions AND implementations in the one cpp file. Do not have a seperate header file for the definitions and a seperate file for the implementation as is customary.

Let us take a look at the example. I strongly suggest you copy this code and compile it and run it on your desktop for a better understanding.

1. #include <stdio.h> 2. 3. class deer{ 4. public: 5. char* getWhat(){return (char*)"I'm a deer";} 6. }; 7. 8. class hog{ 9. public: 10. char* getWhat(){return (char*)"I'm a hog";} 11. }; 12. 13. class buffalo{ 14. public: 15. char* getWhat(){return (char*)"I'm a buffalo";} 16. }; 17. 18. class man{ 19. public: 20. char* getWhat(){return (char*)"I'm a man - dear god";} 21. }; 22. 23. /*Default digestive classes*/ 24. template <typename T> 25. class crocdigest{ 26. public: 27. void digest(T& t){ 28. printf("default template digest %s\n", t.getWhat()); 29. } 30. }; 31. 32. /*Special digestive class*/ 33. template <typename T> 34. class special_crocdigest{ 35. public: 36. void digest(T& t){ 37. printf("special class digest %s\n", t.getWhat()); 38. } 39. }; 40. 41. 42. /*Default croc's meals*/ 43. template <class T, class c_crocdigest = crocdigest<T> > 44. class crocsmeal{ 45. c_crocdigest crocdig; 46. public: 47. int gobble(T&); 48. }; 49. template <typename T, class c_crocdigest> 50. int crocsmeal<T,c_crocdigest>::gobble(T& t){ 51. crocdig.digest(t); 52. return 0; 53. } 54. 55. /*specialized template for hogs meal*/ 56. template <> 57. class crocsmeal<hog>{ 58. public: 59. int gobble(const hog& t){ 60. printf("template specialization gobbling the hog\n"); 61. return 0; 62. } 63. }; 64. 65. 66. int main(){ 67. 68. hog h; 69. deer d; 70. man m; 71. buffalo b; 72. 73. crocsmeal<deer> mealdeer; 74. crocsmeal<hog> mealhog; 75. crocsmeal<buffalo> mealbuffalo; 76. crocsmeal<man, special_crocdigest<man>> mealman; 77. 78. mealhog.gobble(h); 79. mealdeer.gobble(d); 80. mealbuffalo.gobble(b); 81. mealman.gobble(m); 82. } Hide line numbers