1. <string> is the C++ version for string type, <cstring> is the C++ version for string in C, <string.h>is the C version;
2.
// In C, it is correct:
int *pr=NULL;
// in C++, it is correct:
int *pr=0;
// if you want keep
int *pr=NULL;
//in C++ code, you should #include<cstdlib>
3. // 1)
int a=10;
int b=20;
int const *pt=&a; // same as: const int *pt=&a ;
*pt=11; //error
pt=&b; // correct
//2)
int a=10;
int b=20;
int *const pt=&a;
*pt=11; //correct
pt=&b; // error
4. conversion between string and char
//1)
char * ch="caozhiguang";
string str(ch); // from char to string;
string str=ch; // same with above
//2)
string str("caozhiguang");
char *ch;
ch=str.c_str(); // from string to char;
5. avoid repeating include, also a better file framework(at least for me)
//Zhiguang.h
#include <string>
using namespace std;
#ifndef ZHIGUANG_H
#define ZHIGUANG_H
Class Zhiguang
{
public:
Zhiguang();
Zhiguang(string the_name, string the_addr);
string getinfo();
private:
string name;
string address;
static double salary;
}
#endif
//Zhiguang.cpp
//you'd better initialize the static var in this file
#include "Zhiguang.h"
salary=3500; //initialize the static var;
Zhiguang::Zhiguang() { }
Zhiguang::Zhiguang(string the_name, string the_addr) { }
string Zhiguang::getinfo(){ }
//main.cpp
#include "Zhiguang.h" // no need to include the cpp file
using namespace std;
int main()
{
Zhiguang zg;
// do whatever you want
}
6. create one object for the class
//1)
Zhiguang zg;
zg.name;
zg.address;
zg.getinfo();
//2)
Zhiguang zg=Zhiguang();
zg.name;
zg.address;
zg.getinfo();
//3)
Zhiguang *zg=new Zhiguang();
zg->name;
zg->address;
zg->getinfo();
7. default constructor needed to initialize members of built-in type
Zhiguang() : name("zhiguang"), address("Singapore"){ }
Note: for the real initialize order, it would be based on the declaration order in the class declaration.
e.g:
private:
string address;
string name;
in this case, the default constructor would initialize the address first even it is listed in the second place in the constructor.
8. 1) if the member method is const, it means it can not change the object's member variable;
2) for const member, there should be keyword const both in declaration and definition;
3) the const object can only use its const member, while non-const object can access both const and non-const members;
4) for non-const member method,
this could not be changed while
*this could;
for const member method, both
this and
*this could not be changed.
