《设计与实践》一书关于仿函数的疑问

CR苏杭

5.2.5 信息获取和统计 中提到仿函数Class SimpleFunctor
{
public:
    void operator()(int &i)
    {
       .....
    }
};
和如下函数有同样的被调用的方式
SimpleFuncotr(int &i)
{
    ...
}

疑问1
由于成员函数有隐藏参数SimpleFunctor* this，成员函数和普通函数还是有区别的

疑问2
很长，先贴书中代码

1. #include <osg\io_utils>
   
2. #include <osg\TriangleFunctor>
   
3. #include <osg\Drawable>
   
4. #include <osgDB\ReadFile>
   
5. #include <iostream>
   
6. 
   
7. class AttributePrinter : public osg::Drawable::AttributeFunctor
   
8. {
   
9. public :
   
10. typedef osg::Drawable::AttributeType AttributeType;
    
11. inline const char * getTypeName(AttributeType type)
    
12. {
    
13. static const char* typeNames[]=
    
14. {
    
15. "Vertices","Weights","Normals","Colors","Secondary Colors",
    
16. "Fog Coords","Attribute6","Attribute7",
    
17. "Texture Coords 0","Texture Coords 1","Texture Coords 2",
    
18. "Texture Coords 3","Texture Coords 4","Texture Coords 5",
    
19. "Texture Coords 6","Texture Coords 7"
    
20. };
    
21. return typeNames[type];
    
22. }
    
23. 
    
24. template < typename T>
    
25. void printInfo(AttributeType type, unsigned int size, T* front)
    
26. {
    
27. std::cout << "***" << getTypeName(type) <<":" << size <<std::endl;
    
28. for (unsigned int i=0; i<size ;i++)
    
29. {
    
30. std::cout << "(" << *(front + 1) << ");" ;
    
31. }
    
32. std::cout <<std::endl<< std::endl;
    
33. }
    
34. 
    
35. virtual void apply(AttributeType type ,unsigned int size ,float* front)
    
36. {
    
37. printInfo(type,size,front);
    
38. }
    
39. 
    
40. 
    
41. virtual void apply(AttributeType type ,unsigned int size ,osg::Vec2* front)
    
42. {
    
43. printInfo(type,size,front);
    
44. }
    
45. 
    
46. virtual void apply(AttributeType type ,unsigned int size ,osg::Vec3* front)
    
47. {
    
48. printInfo(type,size,front);
    
49. }
    
50. 
    
51. virtual void apply(AttributeType type ,unsigned int size ,osg::Vec4* front)
    
52. {
    
53. printInfo(type,size,front);
    
54. }
    
55. 
    
56. 
    
57. };
    
58. 
    
59. struct TrianglePrinter
    
60. {
    
61. TrianglePrinter()
    
62. {
    
63. std::cout<< "****Triangles***" << std::endl;
    
64. }
    
65. 
    
66. void operator()(const osg::Vec3 & v1,const osg::Vec3 & v2,
    
67. const osg::Vec3 & v3,bool) const
    
68. {
    
69. std::cout << "(" << v1 << ");" << "(" << v2 << ");" << "(" << v3 << ")" << std::endl;
    
70. }
    
71. };
    
72. 
    
73. class FindGeometryVisitor: public osg::NodeVisitor
    
74. {
    
75. public:
    
76. FindGeometryVisitor()
    
77. :osg::NodeVisitor(TRAVERSE_ALL_CHILDREN){}
    
78. virtual void apply(osg::Node &node)
    
79. {
    
80. traverse(node);
    
81. }
    
82. 
    
83. virtual void apply(osg::Geode &node)
    
84. {
    
85. for (unsigned int i=0; i<node.getNumDrawables(); i++)
    
86. {
    
87. osg::Drawable* drawable = node.getDrawable(i);
    
88. if (!drawable)
    
89. {
    
90. continue;
    
91. }
    
92. std::cout << "[" << drawable->libraryName()
    
93. << "::" << drawable->className() << "]" <<std::endl;
    
94. 
    
95. AttributePrinter attrPrinter;
    
96. drawable->accept(attrPrinter);
    
97. 
    
98. // 这里就是疑问产生处
    
99. osg::TriangleFunctor<TrianglePrinter> triPrinter;
    
100. drawable->accept(triPrinter);
     
101. 
     
102. std::cout<< std::endl;
     
103. }
     
104. traverse(node);
     
105. }
     
106. };
     
107. 
     
108. int main(int argc, char** argv)
     
109. {
     
110. osg::ArgumentParser arguments(&argc, argv);
     
111. osg::Node * model = osgDB::readNodeFiles(arguments);
     
112. if (!model)
     
113. {
     
114. model = osgDB::readNodeFile("exported.ive");
     
115. }
     
116. 
     
117. FindGeometryVisitor fgv;
     
118. if (model)
     
119. {
     
120. model->accept(fgv);
     
121. }
     
122. 
     
123. getchar();
     
124. 
     
125. return 0;
     
126. }

复制代码

osg::TriangleFunctor<TrianglePrinter> triPrinter;
drawable->accept(triPrinter);

运行后，triPrinter确实被输出了，也就是重载()被顺利调用，
要达到这个效果我理解应该满足：
1，TriangleFunctor实现了apply()方法
2，在被实现的apply()方法中有一个和TrignlePrinter的操作符()同样参数格式的函数；

通过看源码，1的出处找到了。但是2没有找到。
疑问2：
被重载的()是何时被调用的？

array

include/osg/TriangleFunctor，看一看drawElements的实现

至于drawElements函数的调用时机，看一看Geometry::accept的实现

CR苏杭

呃，geometry::accept的省略下来就是
functor.begin()
  functor.vertex()
functor.end()

functor.end()中 调用了functor::drawarray;
而drawarray调用了operator()
我用的2.8.2。
===
看了2.9.6的trianglefunctor，它的end()里面也是调用了drawarray啊

array

一样吧~~都要调用operator()啊

CR苏杭

嗷。嗷。。嗷。酱。还以为版本更新以后这里变化了。