在我的代码中我有这个：
int enemyNumber = numberType.at(0);
numberType是一个字符串。
string numberType中的第一个字符是＆＃39; 1＆＃39;。但是int enemyNumber在该任务之后变为48。
发生了什么以及如何让敌人成为＆＃39; 1＆＃39;？
答案 0 :(得分：7)
要将具有#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#define INITIAL_SIZE 20
int main( void )
{
/**
* Allocate space to store a string; the +1 is to make sure
* we have space for the 0 terminator.
*/
char *str1 = calloc( INITIAL_SIZE+1, sizeof *str1 );
size_t str1size = INITIAL_SIZE + 1;
/**
* str2 will point to a string literal; literals are stored as
* arrays of char such that they are allocated at program startup
* and held until the program terminates. String literals may
* not be modified, so we're declaring the pointer as const char *.
*/
const char *str2 = " of the Emergency Broadcast System";
/**
* Copy a string to that buffer
*/
strcpy( str1, "This is a test" );
/**
* Extend the buffer to hold more stuff; typical strategy is
* to double the buffer size each time. For this particular
* example this loop should only run once.
*/
while ( strlen( str1 ) + strlen( str2 ) > str1size)
{
char *tmp = realloc( str1, 2 * str1size );
if ( !tmp )
{
// realloc failed, for this example we treat it as a fatal error
exit( -1 );
}
str1 = tmp;
str1size *= 2;
}
/**
* Append to the buffer
*/
strcat( str1, str2 );
// do something interesting with str1 here
/**
* Deallocate the buffer
*/
free( str1 );
return 0;
}
到'0'的值的单个字符转换为相应的数字，请减去'9'的值：
'0'如果您想转换包含多个数字的字符串，标准库可以提供帮助：
int enemyNumber = numberType.at(0) - '0';
答案 1 :(得分：6)
这是因为48是#include <QtCore/QDebug>
#include "pinger.h"
Pinger::Pinger():
_pingUrl("8.8.8.8")
{
}
Pinger::~Pinger()
{
}
void Pinger::startPingCheck(const QString& urlToPing, const int& pingInterval)
{
_pingUrl = urlToPing;
// Listen for messages from the ping process
connect(&_pingProcess, SIGNAL(readyRead()), this, SLOT(_handleProcessMessage()));
// Connect the timer to the exec method that actually calls the ping process
_pingTimer.setInterval(pingInterval * 1000);
_pingTimer.setSingleShot(false);
connect(&_pingTimer, SIGNAL(timeout()), this, SLOT(_pingExec()));
_pingTimer.start();
}
void Pinger::_pingExec()
{
QStringList arguments;
arguments << "-n" << "1" << _pingUrl;
_pingProcess.start("ping", arguments);
}
void Pinger::_handleProcessMessage()
{
QByteArray response = _pingProcess.readAll();
QString responseStr(response);
if(responseStr.contains("100% loss"))
{
qDebug() << "Ping failed. " << _pingUrl << " down.";
emit pingFailed();
}
}
的字符代码。要获取整数值，请推导出类似1的{{1}}。这样，您将获得'0'的字符代码减去int enemyNumber = numberType.at(0) - '0';的字符代码，即'1'。这适用于所有数字，因为它们的字符代码是连续数字。
答案 2 :(得分：1)
如果要保留在字符串对象中，可以执行以下操作：
#include <string>
#include <iostream>
int main()
{
std::string numberType("1234");
const int enemyNumber = std::stoi( numberType.substr(0,1) );
std::cout << enemyNumber;
return 0;
}
stoi（）将为您执行从string到int的转换。