| 差异特性 | struct | class |
|---|---|---|
| 成员访问范围 | 默认public | 默认private |
| 继承关系访问范围 | 默认public | 默认private |
| {}初始化 | 1、纯数据或纯数据+普通方法的结构体支持；2、带构造函数或虚方法的结构体不支持 | 不支持 |
struct Person {
int age;
}
Person person = new Person();
person.age = 12;可以正常的编译和执行。
class Person {
int age;
}
Person person = new Person();
person.age = 12; // 编译出错，应改为public int age;【扩展】如果不增加public关键字，又想在某个类如ClassA中能访问到这个Person类中的成员，可以通过友元类(friend class Xxx)来将Person中的private和protected的成员共享出去。
Person类可以这么编写：
struct Person {
friend class ClassA;
int age;
}
Person person = new Person();
person.age = 12;在ClassA中，就可以访问Person中的所有成员了。
void ClassA:setAge() {
Person *person = new Person();
person->age = 12;
}关于友元类的使用，可见c++论坛：https://cplusplus.com/forum/beginner/147733/
指的是子对象是否可访问到父对象中的成员。
struct SBase {
public:
int age = 0;
SBase() = default;
virtual ~SBase() = default;
};
struct Person : SBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}访问正常：
class CBase {
public:
int age = 0;
CBase() = default;
virtual ~CBase() = default;
};
struct Person : CBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}访问正常。
class CBase {
public:
int age = 0;
CBase() = default;
virtual ~CBase() = default;
};
struct Person : private CBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}编译错误：不可访问。
class CBase {
public:
int age = 0;
CBase() = default;
virtual ~CBase() = default;
};
class Person : CBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}编译错误：不可访问。
class CBase {
public:
int age = 0;
CBase() = default;
virtual ~CBase() = default;
};
class Person : public CBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}访问正常。
struct SBase {
public:
int age = 0;
SBase() = default;
virtual ~SBase() = default;
};
struct Person : SBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}访问正常。
struct SBase {
public:
int age = 0;
SBase() = default;
virtual ~SBase() = default;
};
struct Person : public SBase {
public:
Person() = default;
virtual ~Person() = default;
};
int main(int argc, const char **argv)
{
Person* child = new Person();
child->age = 1;
fprintf(stdout, "test: age=%d\n", child->age);
}访问正常。
【总结】
struct StructA {
void send();
int a;
long b;
string str;
};
void StructA::send()
{
fprintf(stdout, "StructA: sending...\n");
}
int main(int argc, const char **argv)
{
StructA aS = {12, 34, "a test"};
aS.send();
fprintf(stdout, "StructA: a=%d, b=%ld, str=%s\n", aS.a, aS.b, aS.str.c_str());
}可直接用{}初始化数据：
struct StructA {
void send();
int a;
long b;
string str;
StructA();
};
void StructA::send()
{
fprintf(stdout, "StructA: sending...\n");
}
int main(int argc, const char **argv)
{
StructA aS = {12, 34, "a test"};
aS.send();
fprintf(stdout, "StructA: a=%d, b=%ld, str=%s\n", aS.a, aS.b, aS.str.c_str());
}编译失败：
struct StructA {
void virtual send();
int a;
long b;
string str;
};
void StructA::send()
{
fprintf(stdout, "StructA: sending...\n");
}
int main(int argc, const char **argv)
{
StructA aS = {12, 34, "a test"};
aS.send();
fprintf(stdout, "StructA: a=%d, b=%ld, str=%s\n", aS.a, aS.b, aS.str.c_str());
}编译失败：
class ClassA {
int a;
long b;
string str;
};
int main(int argc, const char **argv)
{
ClassA cA = {12, 34, "a test"};
}编译失败：
