轉換

c++中的一些類型轉換 : CString,string,int ,long,double,char*,const char*,date等 收藏

最近做項目用到c++，才發現c++中的數據類型不是一般的BT。尤其是我和婷還是分開操作的。我寫底層，用的是WIN32控制檯；而婷寫MFC。由於沒有經驗，所以沒有寫中間的轉換程序。當集成時，類型轉換特別麻煩。以下都是我收集的類型轉換的方法和一些經驗，供大家參考。歡迎補充~~

1. char* to string
string s(char *);
注：在不是初始化的地方最好用assign().
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2. string to const char*
string a="strte";
const char* r=a.c_str();
注意是const的。還要轉到char*：
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2.2. const char* to char*
const char* r="123";
char *p1 = new char[strlen(r)+1];
strcpy(p1,r);
附：http://hi.baidu.com/cfans/blog/item/06970ef4b671f366dcc4745d.html
這個頁面是具體講述區別的。
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3. cstring to string
vs2005 Unicode下：
CStringW str(L"test");
CStringA stra(str.GetBuffer(0));
str.ReleaseBuffer();
std::string strs (stra.GetBuffer(0));
stra.ReleaseBuffer();

非Unicode下：
CString cs("test");
std::string str=cs.getBuffer(0);
cs.ReleaseBuffer();

注：GetBuffer()後一定要ReleaseBuffer(),否則就沒有釋放緩衝區所佔的空間.
++++++++++++++++++++++++++++++++++++++++++++++++++++
4. double ,int to string
#include <sstream>
using namespace std;

stringstream ss;
string result;
long n=11111;
stream << n; //從long型數據輸入
stream >>result; //轉換爲 string


===================================================

5.char* to int, double ,long

char *s; double x; int i; long l;

s = " -2309.12E-15"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s/tfloat: %e/n", s, x );

s = "7.8912654773d210"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s/tfloat: %e/n", s, x );

s = " -9885 pigs"; /* Test of atoi */
i = atoi( s );
printf( "atoi test: ASCII string: %s/t/tinteger: %d/n", s, i );

s = "98854 dollars"; /* Test of atol */
l = atol( s );
printf( "atol test: ASCII string: %s/t/tlong: %ld/n", s, l );
------------------------------------------------------------------------------------------------
6. string to int ,long ,double
int s;
string str="123";
stringstream ss;
ss<<str;//從str輸入
ss>>s;//輸出到int
ss.clear();


——————————————————————————————————————————
7. date to string
#include <time>
using namespace std;

char dateStr [9];
char timeStr [9];
_strdate( dateStr);
printf( "The current date is %s /n", dateStr);
_strtime( timeStr );
printf( "The current time is %s /n", timeStr);

--------實踐證明是正確的版本--------------------------------------------------------------
#include <iostream>
#include <ctime>
#include <cerrno>

int main()
{
//Find the current time
time_t curtime = time(0);

//convert it to tm
tm now=*localtime(&curtime);

//BUFSIZ is standard macro that expands to a integer constant expression
//that is greater then or equal to 256. It is the size of the stream buffer
//used by setbuf()
char dest[BUFSIZ]={0};

//Format string determines the conversion specification's behaviour
const char format[]="%A, %B %d %Y. The time is %X";

//strftime - converts date and time to a string
if (strftime(dest, sizeof(dest)-1, format, &now)>0)
std::cout<<dest<<std::endl;
else
std::cerr<<"strftime failed. Errno code: "<<errno<<std::endl;
}

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8.string to cstring

+++++++++++++++++++++++++++++++++++++++++++++++++++++
非Unicode下：
int 轉 CString：
CString.Format("%d",int);
...............................
string 轉 CString
CString.format("%s", string.c_str());
用c_str()確實比data()要好.
.......................................
char* 轉 CString
CString.format("%s", char*);
CString strtest;
char * charpoint;
charpoint="give string a value";
strtest=charpoint; //直接付值
.....................................................
CString 轉 int
CString ss="1212.12";
int temp=atoi(ss); //atoi _atoi64或atol
...................................................................................................................................
9.在Unicode下的CString to double
CSting sTemp("123.567");
double dTemp = _wtof(sTemp.GetString());