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这可能是一个重复的问题，但已建立的答案并没有解决我的问题。我正在尝试在 QT 中创建一个客户端服务器应用程序，其中客户端向服务器发送一个字符串消息代码，服务器必须连接到 sql server 数据库并检索与客户端消息代码相关的数据。下面是我到目前为止编写的服务器部分。但我收到此错误：无法打开包含文件：'QtSql'：没有这样的文件或目录。当我制作单独的项目并运行数据库部分时，它工作得很好，但是当我把它们放在一起时，它就失败了。任何人都有一些建议可以解决这个问题？

ServerSocket.pro

QT       += core
QT       += network
QT       += sql
QT       -= gui

TARGET = ServerSocket
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app


SOURCES += main.cpp \
    server.cpp

HEADERS += \
    server.h

服务器套接字.h

#ifndef SERVER_H
#define SERVER_H

#include <QObject>
#include <QDebug>
#include <QTcpServer>
#include <QTcpSocket>


class Server : public QObject
{
    Q_OBJECT
public:
    explicit Server(QObject *parent = 0);

signals:

public slots:
    void newConnection();
private:
    QTcpServer *server;

};

#endif // SERVER_H

服务器套接字.cpp

#include …

考虑下面的代码,如果我使用这样的Die类实例会发生什么:

Die d;
d.Roll(20);
d.Roll(15);
d.Roll(30);

在为内存再次分配内存之前,我应该还是不应该释放值占用的内存？delete[ ]之前new？

die.h

#ifndef DIE_H
#define DIE_H
#include<iostream>
#include<time.h>
using namespace std;


class Die
{
private:
    int number;
    int* values;
    int count;
    void roll();
public:
    Die(){srand(static_cast<int>(time(NULL)));number=0;values=NULL;count=0;}
    void Roll(int n);
    int getNumber()const{return number;}
    void printLastValue();
    void printValues();
    ~Die(){delete [] values;}

};

#endif

die.cpp

#include"die.h"
#include<iostream>
#include<time.h>
using namespace std;

void Die::roll()
{

    number=1+rand()%6;
}

void Die::printLastValue()
{
    cout<<number<<endl;
}

void Die::Roll(int n)
{
    count=n;
    values=new int[count];
    for(int i=0;i<count;i++)
    { …

我知道这个话题已经讨论过,但我花了半天时间来弄清楚我做错了什么.我一直有这个错误,我想我已经完成了数以千计的语法检查.谁能帮我？

#ifndef ADDEDITDIALOG_H
#define ADDEDITDIALOG_H

#include <QDialog>
#include <QStandardItemModel>
#include "characteristics.h"
#include "equipment.h"
#include "generaldata.h"
#include "registration.h"
#include "revisiondialog.h"
#include "vehicle.h"
#include "vehiclehelper.h"
#include "verification.h"
#include "verificationdialog.h"


namespace Ui {
class AddEditDialog;
}

class AddEditDialog : public QDialog
{
Q_OBJECT

public:
explicit AddEditDialog(QWidget *parent = 0);
~AddEditDialog();

bool getIsNew() const;
bool getIsEdited() const;
bool getAddRevision() const;

Vehicle getVehicleToAdd() const;

void setVehicleToAdd();
void loadVehicleToEdit(Vehicle car);
void createTableView(const QList<Verification> list);

QList<Verification> getRevisionsList() const;

private slots:
void on_add_revision_clicked();

void on_save_clicked();

void on_cancel_clicked();

void …

我必须创建一个类直方图并在这个类上进行操作.输入可以是一维阵列或二维阵列.当我将数组转换为矩阵时出现问题.这是我到目前为止所尝试的.错误是<Unable to read memory>

histrogram.h

#ifndef HISTOGRAM_H
#define HISTOGRAM_H
#include<iostream>
class Histogram
{
private:
    int** matrix;
    int lines;
    void SortMatrix();
public:
    Histogram(){ }
    Histogram(int elements[], int elementsNr);
    Histogram(int** m, int l);
    void Print();
};
#endif

historgram.cpp

#include"histogram.h"
using namespace std;
Histogram::Histogram(int** m, int l)
{
    matrix=m;
    lines=l;
    SortMatrix();
}

Histogram::Histogram(int elements[], int elementsNr)
{
    lines=0;
    //initialize matrix : elementrNr lines and 2 columns
    int** matrix=new int*[elementsNr];
    for(int i=0;i<elementsNr;i++)
    {
        matrix[i]=new int[2];
        matrix[i][0]=INT_MIN;
        matrix[i][1]=INT_MIN;
    }
    //search each element from the …

可能重复:
当在单个函数c ++中调用时,rand函数返回相同的值

为什么rand()生成相同的数字？

die.h

#ifndef DIE_H
#define DIE_H


class Die
{
private:
    int number;
public:
    Die(){number=0;}
    void roll();
    int getNumber()const{return number;}
    void printValue();
};

#endif

die.cpp

#include"die.h"
#include<iostream>
#include<time.h>
using namespace std;

void Die::roll()
{
    srand(static_cast<int>(time(0)));
    number=1+rand()%6;
}

void Die::printValue()
{
    cout<<number<<endl;
}

main.cpp中

#include"die.h"
#include<iostream>
using namespace std;

int main()
{
    Die d;
    d.roll();
    d.printValue();
    d.roll();
    d.printValue();
    d.roll();
    d.printValue();
}

我正在遍历列表,我想使用const_iterator.但我不知道该怎么做!到现在为止我使用了iterator并以这种方式实现了我的功能.任何人都可以帮我使用const_iterator吗？

void MainWindow::populate(const QList<Vehicle> &vehicles)
{
int j = 0;
QListIterator<Vehicle> iter(vehicles);    
while(iter.hasNext()){
    Vehicle car = iter.next();
    //set car
    QString makeAndModel = car.getGeneralData().getMake() + car.getGeneralData().getModel();
    QStandardItem *mAndM = new QStandardItem(QString(makeAndModel));
    mAndM->setEditable(false);
    model->setItem(j,0,mAndM);

    //set type
    QStandardItem *type = new QStandardItem(QString(car.getGeneralData().getType()));
    type->setEditable(false);
    model->setItem(j,1,type);

    //set mileage
    QString mileageString = QString::number(car.getGeneralData().getMileage());
    QStandardItem *mileage = new QStandardItem(QString(mileageString));
    mileage->setEditable(false);
    model->setItem(j,2,mileage);

    //set year
    QString yearString = QString::number(car.getGeneralData().getYear());
    QStandardItem *year = new QStandardItem(QString(yearString));
    year->setEditable(false);
    model->setItem(j,3,year);

    //set registration
    QString regString = VehicleHelper::convertBoolToString(car.getRegistration().isRegistered());
    QStandardItem *regDate = new QStandardItem(QString(regString));
    regDate->setEditable(false);
    model->setItem(j,4,regDate); …

调试后我收到此错误消息:正常块后检测到HEAP CORRUPTION(#55).如果我增加阵列的大小(no_of_days+1),它正在工作,但我不知道它是否正确.我做错了什么？

int main()
{

    int no_of_days=0;
    int no_operations=0;
    int *a;
    int i;
    FILE *pfile1=NULL;
    FILE *pfile2=NULL;
    char *filename1="input.txt";
    char *filename2="output.txt";

    pfile1=fopen(filename1, "r");
    if(pfile1==NULL)
    {
        printf("Error on opening the file %s.",filename1);
        return 0;
    }
    fscanf(pfile1,"%d%d",&no_of_days,&no_operations);
    a=(int*)malloc((no_of_days)*sizeof(int));
    if(a==NULL)
    {
        printf("Memory allocation failed.");
        return 0;
    }
    for(i=1;i<=no_of_days;i++)
    {
        fscanf(pfile1,"%d",&a[i]);
    }
    pfile2=fopen(filename2,"a");
    if(pfile2==NULL)
    {
        printf("Memory allocation failed!",filename2);
    }
    for(i=1;i<=no_of_days;i++)
    {
        fprintf(pfile2,"%d",a[i]);
    }
    free(a);
    fclose(pfile1);
    fclose(pfile2);

我@OneToOne在以下表格之间存在双向关系：

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table
public class StudentAccount implements DomainModel {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer idstudentaccount;
    @OneToOne(optional = false)
    @JoinColumn(name = "idstudent")
    private Student student;
    private String username;
    private String password;
    //getters and setters
}



@Entity
@Table(name = "student")
public class Student implements DomainModel {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer idStudent;
    private String firstname;
    private String lastname;
    @OneToOne(mappedBy = "student", cascade = CascadeType.ALL, targetEntity=StudentAccount.class)
    private …