Question

以下是我的功能，它假设列出一些国家/地区我尝试使用＆lt;＆lt;固定，但似乎没有帮助

这是我的输出：

�ѿra
�ѿd Arab Emirates
�ѿnistan
�ѿua and Barbuda
�ѿlla
�ѿia
�ѿia
�ѿrlands Antilles
�ѿa
�ѿctica
�ѿtina
�ѿcan Samoa

我的文本文件没问题，我想知道我的数据投放是否有问题。

这是我的CountryData.cpp文件

#include <iostream>
#include <string.h>
#include "CountryData.h"

using namespace std;
// ====================================================================

void readData ()
{
    FILE * pFile;
    NoOfRecordsRead = 0;
    char buffer [Line_Char_Buffer_Size];

    pFile = fopen (INPUT_FILE_NAME , "r");

    if (pFile == NULL) 
        perror ("Error opening file 'Countries.txt' !");
    else
    {
        while ( !feof (pFile) )
        {
            char* aLine = get_line (buffer, Line_Char_Buffer_Size, pFile);

            if (aLine != NULL)
            {
//              printf ("%d] aLine => %s\n", NoOfRecordsRead, aLine);
                globalCountryDataArray [NoOfRecordsRead++] = createCountryRecord (aLine);
            }
        }

     fclose (pFile);

    }
}

// ====================================================================

char* get_line (char *s, size_t n, FILE *f)
{
    char *p = fgets (s, n, f);

    if (p != NULL) 
    {
        size_t last = strlen (s) - 1;
        if (s[last] == '\n') 
            s[last] = '\0';
    }
    return p;
}

// ====================================================================

CountryRecordType createCountryRecord (char* aLine)
{
    CountryRecordType ctryRec;
    char* pch = strtok (aLine, LINE_DATA_DELIMITER);

    // 1) Retrieve TLD
    strcpy (ctryRec.TLD, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 2) Retrieve Country
    strcpy (ctryRec.Country, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 3) Retrieve FIPS104
    strcpy (ctryRec.FIPS104, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 4) Retrieve ISO2
    strcpy (ctryRec.ISO2, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 5) Retrieve ISO3
    strcpy (ctryRec.ISO3, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 6) Retrieve ISONo
    ctryRec.ISONo = atof (pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 7) Retrieve Capital
    strcpy (ctryRec.Capital, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 8) Retrieve Region
    strcpy (ctryRec.Region, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 9) Retrieve Currency
    strcpy (ctryRec.Currency, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 10) Retrieve CurrencyCode
    strcpy (ctryRec.CurrencyCode, pch);
    pch = strtok (NULL, LINE_DATA_DELIMITER);

    // 11) Retrieve Population
    ctryRec.Population = atof (pch);

    return (ctryRec);

}

// ====================================================================

char* displayRecordContent (CountryRecordType ctryRec)
{
    char * output = ctryRec.Country;
    return output;

}

// ====================================================================

void showAllRecords ()
{
    int i=0;
    string stroutput;
    char * result;
    for (i=0; i<NoOfRecordsRead; i++)
    {

        result = displayRecordContent (globalCountryDataArray [i]);
        stroutput += result;
        stroutput += "\n";
    }

cout << fixed << stroutput << endl;

}

// ====================================================================

int findCountryRecord (const char* countryName)
{
    int idx     = -1;
    int found   = 0;

    while (!found && (++idx < Max_Record_Size))
        if (strcmp (globalCountryDataArray [idx].Country, countryName) == 0)
            found = 1;

    if (found)
        return (idx);
    else
        return (-1);
}

// ====================================================================

char* getCapital (const char* countryName)
{
    int idx = findCountryRecord (countryName);

    if (idx < 0)
    {
        printf ("Country '%s' not found!\n", countryName);
        return (NULL);  
    }
    else
        return (globalCountryDataArray [idx].Capital);
}

// ====================================================================

char* getCurrencyCode (const char* countryName)
{
    int idx = findCountryRecord (countryName);

    if (idx < 0)
    {
        printf ("Country '%s' not found!\n", countryName);
        return (NULL);  
    }
    else
        return (globalCountryDataArray [idx].CurrencyCode);
}


// ====================================================================

main ()
{
    readData ();
    showAllRecords ();


}

这是我的CountryData.h文件

#ifndef COUNTRY_DATA_H
#define COUNTRY_DATA_H

// ====================================================================

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

using namespace std;
// ====================================================================

#define TLD_LEN             2
#define COUNTRY_LEN         100
#define FIPS104_LEN         2
#define ISO2_LEN            2
#define ISO3_LEN            3
#define CAPITAL_LEN         100
#define REGION_LEN          100
#define CURRENCY_LEN        50
#define CURRENCY_CODE_LEN   3

#define No_Of_Rec_Fields        11
#define Max_Record_Size         250
#define Line_Char_Buffer_Size   400

#define LINE_DATA_DELIMITER     ","
#define INPUT_FILE_NAME         "Countries.txt"

// ====================================================================

//const char*   LINE_DATA_DELIMITER     = ",";
//const char*   INPUT_FILE_NAME         = "Countries.txt";


typedef struct CountryRecord
{
    char TLD            [TLD_LEN+1];            // Top Level Domain code
    char Country        [COUNTRY_LEN+1];    
    char FIPS104        [FIPS104_LEN+1];        // Ctry code according to FIPS104 standard
    char ISO2           [ISO2_LEN+1];           // Ctry code according to ISO2    standard
    char ISO3           [ISO3_LEN+1];           // Ctry code according to ISO3    standard
    double ISONo;

    char Capital        [CAPITAL_LEN+1];    
    char Region         [REGION_LEN+1];         // E.g. Asia, Europe, etc.
    char Currency       [CURRENCY_LEN+1];       // Full name of currency
    char CurrencyCode   [CURRENCY_CODE_LEN+1];  // Currency abbreviation
    double Population;

}   CountryRecordType;

int NoOfRecordsRead;
CountryRecordType globalCountryDataArray [Max_Record_Size];

// ====================================================================

void readData ();
char* get_line (char *s, size_t n, FILE *f);
CountryRecordType createCountryRecord (char* aLine);
char* displayRecordContent (CountryRecordType ctryRec);
void showAllRecords ();

int findCountryRecord (const char* countryName);
char* getCapital (const char* countryName);
char* getCurrencyCode (const char* countryName);

// ====================================================================

#endif // COUNTRY_DATA_H

这是我的countries.txt文件的一部分

AD,Andorra,AN,AD,AND,20.00,Andorra la Vella,Europe,Euro,EUR,67627.00
AE,United Arab Emirates,AE,AE,ARE,784.00,Abu Dhabi,Middle East,UAE Dirham,AED,2407460.00
AF,Afghanistan,AF,AF,AFG,4.00,Kabul,Asia,Afghani,AFA,26813057.00
AG,Antigua and Barbuda,AC,AG,ATG,28.00,Saint John's,Central America and the Caribbean,East Caribbean Dollar,XCD,66970.00
AI,Anguilla,AV,AI,AIA,660.00,The Valley,Central America and the Caribbean,East Caribbean Dollar,XCD,12132.00
AL,Albania,AL,AL,ALB,8.00,Tirana,Europe,Lek,ALL,3510484.00
AM,Armenia,AM,AM,ARM,51.00,Yerevan,Commonwealth of Independent States,Armenian Dram,AMD,3336100.00
AN,Netherlands Antilles,NT,AN,ANT,530.00,Willemstad,Central America and the Caribbean,Netherlands Antillean guilder,ANG,212226.00
AO,Angola,AO,AO,AGO,24.00,Luanda,Africa,Kwanza,AOA,10366031.00
AQ,Antarctica,AY,AQ,ATA,10.00,--,Antarctic Region, , ,0.00
AR,Argentina,AR,AR,ARG,32.00,Buenos Aires,South America,Argentine Peso,ARS,37384816.00
AS,American Samoa,AQ,AS,ASM,16.00,Pago Pago,Oceania,US Dollar,USD,67084.00
AT,Austria,AU,AT,AUT,40.00,Vienna,Europe,Euro,EUR,8150835.00
AU,Australia,AS,AU,AUS,36.00,Canberra,Oceania,Australian dollar,AUD,19357594.00

Answer 1

由于您将CountryRecordType的值传递给displayRecordContent，因此返回的指针无效，使用它会导致未定义的行为。这是因为您返回一个指向函数调用期间所创建的副本所持有的内容的指针，该函数在函数返回时被破坏。

修改您的displayRecordContent功能，改为使用传递参考。

const char* displayRecordContent (const CountryRecordType &ctryRec)
{
    const char * output = ctryRec.Country;
    return output;

}

Answer 2

我从头开始重写代码，尝试实际使用C ++而不是C，并将几个C ++混合在一起。

#include <vector>
#include <string>
#include <iostream>
#include <iterator>
#include <fstream>

struct CountryRecord { 
    std::string TLD;
    std::string Country;
    std::string FIPS104;
    std::string ISO2;
    std::string ISO3;
    double ISONo;
    std::string Capital;
    std::string Region;
    std::string Currency;
    std::string CurrencyCode;
    double Population;
};

template <class T>
std::istream &get_field(std::istream &is, T &field) {
    is >> field;
    is.ignore(1);
    return is;
}

template<>
std::istream &get_field<std::string>(std::istream &is, std::string &field) {
    return std::getline(is, field, ',');
}

std::istream &operator>>(std::istream &is, CountryRecord &r) { 
    get_field(is, r.TLD);
    get_field(is, r.Country);
    get_field(is, r.FIPS104);
    get_field(is, r.ISO2);
    get_field(is, r.ISO3);
    get_field(is, r.ISONo);
    get_field(is, r.Capital);
    get_field(is, r.Region);
    get_field(is, r.Currency);
    get_field(is, r.CurrencyCode);
    return get_field(is, r.Population);
}

std::ostream &operator<<(std::ostream &os, CountryRecord const &r) { 
    return os << r.Country;
}

int main() { 
    std::ifstream in("countries.txt");
    std::vector<CountryRecord> countries(
        (std::istream_iterator<CountryRecord>(in)),
        std::istream_iterator<CountryRecord>());

    std::copy(countries.begin(), countries.end(), 
              std::ostream_iterator<CountryRecord>(std::cout, "\n"));

    return 0;
}

C ++奇怪的输出与printf

2 个答案: