c++ class 用法中的 try catch 块

Question

这是导致错误的 v1

#include <iostream>
#include "exceptionHandlingV2.h"
using namespace std;
int main() {
    exceptionHandlingV2 ob(4,0);
    cout<<ob.divide();
    cout<<"\nbye";
    return 0;
}

#ifndef EXCEPTION_HANDLING_V2_EXCEPTIONHANDLINGV2_H
#define EXCEPTION_HANDLING_V2_EXCEPTIONHANDLINGV2_H
#include <iostream>
using namespace std;

class exceptionHandlingV2 {
private:
    int numerator;
    int denominator;
    string error;
public:
    exceptionHandlingV2();
    exceptionHandlingV2(int ,int);

    void setDenominator(int );
    void setNumerator(int );

    void readAgain ();
    void print_errors();

    double divide() const;
};
#endif //EXCEPTION_HANDLING_V2_EXCEPTIONHANDLINGV2_H

#include "exceptionHandlingV2.h"
exceptionHandlingV2::exceptionHandlingV2(){
    numerator=1;
    denominator=1;
}
exceptionHandlingV2::exceptionHandlingV2(int numerator,int denominator){
    setNumerator(numerator);
    try {
        setDenominator(denominator);
        error = "";
    }catch (const char * e){
        error = e;
        print_errors();
        readAgain();
    }
}

void exceptionHandlingV2::setDenominator(int denominator){
    if ( denominator == 0 ){
        throw "divided by zero\n";
    }

    (*this).denominator = denominator;
}

void exceptionHandlingV2::readAgain (){
    int temp;
    cout<<"enter denominator again other than 0\n";
    cin >> temp;
    exceptionHandlingV2 ( numerator,temp );
}
void exceptionHandlingV2::print_errors(){
    cout<<error;
}
void exceptionHandlingV2::setNumerator(int numerator){
    (*this).numerator = numerator;
}

double exceptionHandlingV2::divide() const{
    return (double)numerator/denominator;
}

这是 v2 设计，我在构造函数中停止与用户交互

exceptionHandlingV2::exceptionHandlingV2(int numerator,int denominator){
    setNumerator(numerator);
    setDenominator( denominator );
}

void exceptionHandlingV2::setDenominator(int denominator){

    try
    {
        if ( denominator == 0 )
            throw "divided by zero\n";

        (*this).denominator = denominator;
        error = "";
    }
    catch (const char * e)
    {
        error = e;
        print_errors();
        readAgain();
    }

}

在 v3 设计中，我添加了一个新函数来处理 class 自身内部的异常

exceptionHandlingV4::exceptionHandlingV4(int numerator,int denominator){
    setNumerator(numerator);
    setDenominator( denominator );
}

void exceptionHandlingV4::setDenominator(int denominator){

    try {
        runtime_set_denominator_error ( denominator );

    }
    catch ( const char *e )
    {
        error = e;
        print_errors();
        readAgain();
    }
}

void exceptionHandlingV4 :: runtime_set_denominator_error  ( int denominator ){

    if ( !denominator )
        throw "divided by zero \n";
  
    (*this).denominator = denominator;
    error = "";
}

我做了一个 v4 设计来停止在 class 中处理异常，而是在 main() 中进行。哪一个是正确的？在 class 中处理异常，或者只是从 class 中抛出异常并在 main 中处理？，问题是我不能再继续从用户读取 readAgain() 直到用户输入写输入，因为异常将会消失在 catch 块内，无法处理 catch 块中的运行时错误，所以我从设计中删除了 readagain() 函数，只在 main() 部分

中打印错误

exceptionHandlingV5::exceptionHandlingV5(int numerator,int denominator){
    setNumerator(numerator);
    setDenominator( denominator );
}
void exceptionHandlingV5::setDenominator(int denominator){

        if ( !denominator ){
            error = "divided by zero \n";
            throw "divided by zero\n";
        }

    (*this).denominator = denominator;
        error = "";
}

//and also I had to move obj creation 
//out of try block, and therefore 
//because of set_denominator(); handles exception
// I had to forget initializing when creating obj 
//and instead used set methods 
int main() {

     exceptionHandlingV5 ob;

    ob.setNumerator(4);

    try {
        ob.setDenominator(0);
        // logic
        cout << ob.divide();
    }
    catch(char const *e)
    {
       // I can only print errors now
       // can't keep reading
        ob.print_errors();
    }
}

Answer 1

感谢@sonulohani、@RichardCritten 和@molbdnilo 指导我并修改了我的愚蠢问题，我的意思是现在我看看我的第一个设计，我发现我犯了很多错误和错误通过您的帮助和评论。无论如何，我最终修改了我的整个设计并为 division 制作了一个新的 class 和 main() 函数。我一开始想做的就是从 class 练习运行时错误处理，现在我想我终于明白了。这是最后一个设计。它可能会帮助将来的人。

#ifndef EXCEPTION_HANDLING_FINAL_V1_EXCEPTION_HANDLING_FINAL_V1_H
#define EXCEPTION_HANDLING_FINAL_V1_EXCEPTION_HANDLING_FINAL_V1_H
class exception_handling_final_v1 {
private:
    double numerator;
    double denominator;
    char * error;
public:
    exception_handling_final_v1();
    exception_handling_final_v1( double , double );

    void set_numerator ( double );
    void set_denominator ( double );

    double divide ( );
    char * errors();
};
#endif //EXCEPTION_HANDLING_FINAL_V1_EXCEPTION_HANDLING_FINAL_V1_H

#include "exception_handling_final_v1.h"
exception_handling_final_v1::exception_handling_final_v1() {
    numerator = 1;
    denominator = 1;
    error = "";
}
exception_handling_final_v1::exception_handling_final_v1( double numerator,
                                                          double denominator) {
    set_numerator( numerator );
    set_denominator ( denominator );
}
void exception_handling_final_v1::set_numerator ( double numerator ){
    (*this).numerator = numerator;
}
void exception_handling_final_v1::set_denominator( double denominator ) {
    if ( !denominator ){
        error = "denominator can not be zero\n";
        throw "denominator can not be zero\n";
    }
    (*this).denominator = denominator;
    error = "";
}
double exception_handling_final_v1 :: divide () {
    return denominator / numerator;
}
char * exception_handling_final_v1::errors() {
    return error;
}

#include <iostream>
#include "exception_handling_final_v1.h"
using namespace std;

int main() {

    exception_handling_final_v1 ob;
    double numerator , denominator , result;
    cout << "enter nummerator\n";
    cin >> numerator;
    ob.set_numerator( numerator );

    cout << "enter denominator\n";
    cin >> denominator ;

    try{
        ob.set_denominator( denominator );
        result = ob.divide();
    }
    catch( char const * error){
        cout << ob.errors();
    }

    cout<<"bye";
    return 0;
}

c++ class 用法中的 try catch 块

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