函数指针类型别名与智能指针

Posted 2020-09-09 jz_cnblogs

 1 // run in windows: std::system("pause")
 2 #include <cstdlib>
 3 #include <iostream>
 4 #include <memory>
 5 #include <functional>
 6 
 7 using namespace std;
 8 using namespace std::placeholders;
 9 
10 template <typename T>
11 using DeleteFunc = void(T*);
12 
13 class Deleter;
14 
15 template <typename T>
16 using DeleteMemberFunc = void(__thiscall Deleter::*)(T*)const;
17 
18 // normal version
19 template <typename T>
20 inline void Delete(T* ptr)
21 {
22     cout << "[delete] address: " << ptr << ", value: " << *ptr << endl;
23     delete ptr;
24 }
25 
26 // caller operator & static member function
27 class Deleter
28 {
29 public:
30     Deleter() = default;
31     ~Deleter() = default;
32     Deleter(const Deleter&) = default;
33     Deleter(Deleter&&) = default;
34     Deleter& operator=(const Deleter&) = default;
35 
36     template <typename T>
37     void operator()(T* ptr) const { Delete(ptr); }
38 
39     template <typename T>
40     static void StaticDelete(T* ptr) { ::Delete(ptr); }
41 } deleter;
42 
43 // std::function
44 function<DeleteFunc<int>> funcobj = &Delete<int>;
45 function<DeleteFunc<int>> static_funcobj = &Deleter::StaticDelete<int>;
46 function<DeleteFunc<int>> member_funcobj = bind(&Deleter::operator()<int> , &deleter, _1);
47 
48 // lambda
49 auto lambda_delete = [](int* ptr) { Delete(ptr); };
50 
51 using IntSPtr = shared_ptr<int>;
52 template <typename Func> using IntUPtr = unique_ptr<int, Func>;
53 
54 int main(int argc, char* argv[])
55 {
56     {
57         DeleteMemberFunc<int> member_func = &Deleter::operator();
58 
59         IntSPtr s1 = make_shared<int>(10);
60         IntSPtr s2(new int(11), &Delete<int>);
61         IntSPtr s3(new int(12), Deleter());
62         IntSPtr s4(new int(13), &Deleter::StaticDelete<int>);
63         IntSPtr s5(new int(14), funcobj);
64         IntSPtr s6(new int(15), static_funcobj);
65         IntSPtr s7(new int(16), member_funcobj);
66         IntSPtr s8(new int(17), lambda_delete);
67         int* sp9 = new int(18);
68         (deleter.*member_func)(sp9);
69 
70         unique_ptr<int> u1 = make_unique<int>(20);
71         IntUPtr<DeleteFunc<int>*> u2(new int(21), &Delete<int>);
72         IntUPtr<Deleter> u3(new int(22), Deleter());
73         IntUPtr<DeleteFunc<int>*> u4(new int(23), &Deleter::StaticDelete<int>);
74         IntUPtr<decltype(funcobj)> u5(new int(24), funcobj);
75         IntUPtr<decltype(static_funcobj)> u6(new int(25), static_funcobj);
76         IntUPtr<decltype(member_funcobj)> u7(new int(26), member_funcobj);
77         IntUPtr<decltype(lambda_delete)> u8(new int(27), lambda_delete);
78         int* up9 = new int(28);
79         (deleter.*member_func)(up9);
80     }
81 
82     std::system("pause");
83     return 0;
84 }