C构造函数与析构函数构造函数和析构函数是C类的特殊成员函数负责对象的初始化和清理工作。理解它们的工作机制对于编写正确的C代码至关重要。默认构造函数在没有参数的情况下创建对象。#include#include#includeclass Person {std::string name_;int age_;public:Person() : name_(Unknown), age_(0) {std::cout Default constructor called\n;}Person(const std::string name, int age) : name_(name), age_(age) {std::cout Parameterized constructor called for name_ \n;}~Person() {std::cout Destructor called for name_ \n;}void display() const {std::cout Name: name_ , Age: age_ \n;}};void constructor_basics() {Person p1;Person p2(Alice, 30);p1.display();p2.display();}成员初始化列表是初始化成员变量的首选方式比在构造函数体内赋值更高效。class Rectangle {const int width_;const int height_;int area_ref_;int area_;public:Rectangle(int w, int h, int ref): width_(w), height_(h), area_ref_(ref), area_(w * h) {std::cout Rectangle constructed: width_ x height_ \n;}int area() const { return area_; }};void initializer_list_example() {int external_area 0;Rectangle rect(10, 20, external_area);std::cout Area: rect.area() \n;}委托构造函数允许一个构造函数调用同一个类的另一个构造函数。class Point {int x_, y_;public:Point() : Point(0, 0) {std::cout Default constructor delegates\n;}Point(int x) : Point(x, 0) {std::cout Single parameter constructor delegates\n;}Point(int x, int y) : x_(x), y_(y) {std::cout Main constructor: ( x_ , y_ )\n;}void display() const {std::cout Point( x_ , y_ )\n;}};void delegating_constructor() {Point p1;Point p2(5);Point p3(3, 4);}拷贝构造函数用于从另一个对象创建新对象。class Array {int* data_;size_t size_;public:explicit Array(size_t size) : data_(new int[size]), size_(size) {std::cout Constructor: allocated size_ ints\n;}Array(const Array other) : data_(new int[other.size_]), size_(other.size_) {std::copy(other.data_, other.data_ size_, data_);std::cout Copy constructor: copied size_ ints\n;}~Array() {delete[] data_;std::cout Destructor: freed memory\n;}size_t size() const { return size_; }};void copy_constructor_example() {Array arr1(10);Array arr2 arr1;Array arr3(arr1);}移动构造函数通过转移资源所有权来避免不必要的拷贝。class String {char* data_;size_t length_;public:String(const char* str ) {length_ strlen(str);data_ new char[length_ 1];strcpy(data_, str);std::cout Constructor: data_ \n;}String(const String other) : length_(other.length_) {data_ new char[length_ 1];strcpy(data_, other.data_);std::cout Copy constructor: data_ \n;}String(String other) noexcept : data_(other.data_), length_(other.length_) {other.data_ nullptr;other.length_ 0;std::cout Move constructor\n;}~String() {delete[] data_;}const char* c_str() const { return data_ ? data_ : ; }};void move_constructor_example() {String s1(Hello);String s2 std::move(s1);String s3 String(World);}explicit关键字防止隐式类型转换。class Integer {int value_;public:explicit Integer(int v) : value_(v) {}int value() const { return value_; }};void explicit_constructor() {Integer i1(42);std::cout Value: i1.value() \n;}析构函数在对象生命周期结束时自动调用用于释放资源。class File {FILE* file_;std::string filename_;public:explicit File(const std::string filename) : filename_(filename) {file_ fopen(filename.c_str(), w);if (file_) {std::cout File opened: filename_ \n;}}~File() {if (file_) {fclose(file_);std::cout File closed: filename_ \n;}}void write(const std::string data) {if (file_) {fwrite(data.c_str(), 1, data.size(), file_);}}File(const File) delete;File operator(const File) delete;};void destructor_example() {File file(test.txt);file.write(Hello, World!\n);}虚析构函数确保通过基类指针删除派生类对象时正确调用派生类的析构函数。class Base {public:Base() {std::cout Base constructor\n;}virtual ~Base() {std::cout Base destructor\n;}};class Derived : public Base {int* data_;public:Derived() : data_(new int[100]) {std::cout Derived constructor\n;}~Derived() override {delete[] data_;std::cout Derived destructor\n;}};void virtual_destructor_example() {Base* ptr new Derived();delete ptr;}构造函数和析构函数的调用顺序遵循特定规则理解这些规则对于避免资源泄漏很重要。class Component {std::string name_;public:explicit Component(const std::string name) : name_(name) {std::cout Component name_ constructed\n;}~Component() {std::cout Component name_ destructed\n;}};class System {Component comp1_;Component comp2_;public:System() : comp1_(A), comp2_(B) {std::cout System constructed\n;}~System() {std::cout System destructed\n;}};void construction_order() {System sys;}构造函数和析构函数是RAII模式的基础确保资源的正确管理。