A summary of the transition between CString, char *, char [], string, int, double

Note: The fp variable in the below is defined by myself. You can ignore it.
Please also take your attention:
1. The CString is a wide string(word not byte), which is a part of MFC. The others are narrow string.
2. They are run in visual studio.

1. char * to CString

method 1: Use Format

char *temp = "Hello MFC";

CString str;

str.Format(L"%S\n", temp);
//Notice that S is uppercase, otherwise it will be garbled

MessageBox(str);

Method 2: Use the constructor directly

char *temp1 = "你好";

CString str1(temp1); 
//This way will not be garbled code, use method one, 
//Chinese will be garbled code

MessageBox(str1);

2. CString to char *

CString str("Hello MFC");
CString str1("你好");

//This must be in the closest position before using T2A
USES_CONVERSION;
char *buf = T2A(str);
char *buf1 = T2A(str1);

3. char [] to CString

Method 1: Use Format

char temp[10] = "Hello MFC";

CString str;
str.Format(L"%S\n", temp);
//Notice that S is uppercase, otherwise it will be garbled
MessageBox(str);

Method 2: Use the constructor directly

char temp1[10] = "你好";
CString str1(temp1); 
//This way will not be garbled code, use method one, 
//Chinese will be garbled code

MessageBox(str1);

4. CString to char[]

//First convert CString to char *
CString str1("你好");

//This must be in the closest position before using T2A
USES_CONVERSION;
char *buf = T2A(str);

//Use strcpy convert char* to char[]
char temp[10];
strcpy(temp, buf1);
fprintf(fp, "%s\n", temp);

5. string to char*

string s1 = "abc你好";
const char *tt = s1.c_str();
const char *t = s1.data();
fprintf(fp,"%s\t%s\n", tt, t);

6. char* to string

char *temp = "abc你好";
string str = temp;
fprintf(fp, "%s\n", str.c_str());

7. char[] to string

char temp[14] = "abc你好def";
string str = temp;
fprintf(fp, "%s\n", str.c_str());

8. string to char[]

method 1: First convert string to char *, then convert to char[]

string str = "hello world";
const char *temp = str.c_str();
char temp1[20];
strcpy(temp1, temp);
fprintf(fp, "%s\n", temp);

method 2: Convert byte by byte

string str = "hello world";
char temp2[20];
int i = 0;
for (i = 0; i < str.length(); i++) {
	temp2[i] = str[i];
}
temp2[i] = '\0';
fprintf(fp, "%s\n", temp2);

9. int to char*

Method 1: Use sprintf

int i = 123;
char str[10];
sprintf(str, "%d", i);
fprintf(fp, "%s\n", str);

Method 2: Use _itoa

 
int number = 12345;
char str[32];
_itoa(number, str, 10); 
//The third parameter means the scale. 10 means dec, 2 means binary.
fprintf(fp, "%s\n", str);

10. char * to int

char *str = "123";
int num = atoi(str);
fprintf(fp, "%d\n", num);

11. int，double to CString

int a = 123;
double b = 123.4;
CString str;
str.Format(L"%d %lf", a, b);
MessageBox(str);

12. CString to int,double

CString str("123");
int num = _ttoi(str);
fprintf(fp, "%d\n", num);

CString str1("123.4");
double num1 = _ttof(str1);
fprintf(fp, "%lf\n", num1);

13. int，double to string

int num = 123;
double number = 123.4;

string sss = to_string(num);
string str = to_string(number);
fprintf(fp, "%s, %s\n", sss.c_str(), str.c_str());

//Can't use fprintf(fp, "%s, %s\n", sss, str); 
//Because sss is the string type，it belongs to STL container. 
//but %s format means to print string. sss.c_str() is the string.

14. string to int，double

string ss = "124";
string sss = "123.4";
int num = atoi(ss.c_str());
double number = atof(sss.c_str());
fprintf(fp, "%d, %lf\n", num, number);

Have fun.

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