c++ - 在一次调用中重置使用 iomanip : setprecision, setfill 和标志所做的所有更改的类

Question

所以我知道有很多次我想重置我使用 iomanip 所做的格式更改。我创建了一个类，您可以使用它来获取 ostream 对象的格式，例如用于写入/读取文件的 std::cout 或 fstream 对象也可以。我这样做主要是为了练习并帮助其他有同样问题的人。

您所要做的就是使用 ResetIOmanip 类创建一个对象。如果您创建时不带参数，它将使用 std::cout 作为默认值。您可以将 ostream/istream 对象作为参数放入，它将对文件起作用。确保在进行任何格式更改之前调用它。然后当它完成时从对象调用成员函数 resetAll() ，它将重置标志、重置精度和重置填充字符。

请随时就如何改进我的头文件提出意见。我仍在学习，并且一直在寻找建设性的批评。谢谢。

Answer 1

这是头文件:

ResetIOmanip.h

/*
File:   ResetIOmanip.h
Author: kingcobra1986
Date:   7/11/2016
Class:  ResetIOmanip
Purpose: 
        When the instance of the class ResetIOmanip is created, the 
        current settings will be saved and can be recalled by calling
        the member function resetAll().
*/

#ifndef _RESETIOMANIP
#define _RESETIOMANIP
#include <iostream>
#include <iomanip>

class ResetIOmanip {
private:
    std::ostream * _ostream;
    std::istream * _istream;
    std::streamsize _precision;
    std::ios_base::fmtflags _flags;
    char _fill;

    //Set the original precision
    void set_precision () {
        if (this->_ostream != nullptr)
            this->_precision = this->_ostream->precision ();
        if (this->_istream != nullptr)
            this->_precision = this->_istream->precision ();
    }

    //Set the original flags
    void set_flags () { 
        if (this->_ostream != nullptr)
            this->_flags = this->_ostream->flags ();
        if (this->_istream != nullptr)
            this->_flags = this->_istream->flags ();
    }

    //Set the original fill
    void set_fill () { 
        if (this->_ostream != nullptr)
            this->_fill = this->_ostream->fill ();
        if (this->_istream != nullptr)
            this->_fill = this->_istream->fill ();
    }

public:
    //Default Constructor
    ResetIOmanip ( std::ostream & stream = std::cout ) {
        this->_ostream = &stream;
        this->_istream = nullptr;
        this->set_precision ();
        this->set_flags ();
        this->set_fill ();
        stream << "Fill: " << this->get_fill () << std::endl;
    }

    //Overloaded Constructor
    ResetIOmanip ( std::istream & stream ) {
        this->_ostream = nullptr;
        this->_istream = &stream;
        this->set_precision ();
        this->set_flags ();
        this->set_fill ();
    }

    //Get the original precision
    std::streamsize get_precision () { return this->_precision; }

    //Get the original flags
    std::ios_base::fmtflags get_flags () { return this->_flags; }

    //Get the original fill
    char get_fill () { return this->_fill; }

    //Reset to the original precision
    void reset_precision () {
        if (this->_ostream != nullptr)
            this->_ostream->precision ( this->_precision );
        if (this->_istream != nullptr)
            this->_istream->precision ( this->_precision );
    }

    //Reset to the original flags
    void reset_flags () {
        if (this->_ostream != nullptr)
            this->_ostream->flags ( this->_flags );
        if (this->_istream != nullptr)
            this->_istream->flags ( this->_flags );
    }

    //Reset to the original fill
    void reset_fill () { 
        if (this->_ostream != nullptr) {
            this->_ostream->fill ( this->_fill );
        }
        if (this->_istream != nullptr)
            this->_istream->fill ( this->_fill );
    }

    //Reset to all of the original settings
    void resetAll () {
        this->reset_precision ();
        this->reset_flags ();
        this->reset_fill ();
    }
};

#endif

我是这样测试的:

main.cpp

//This is to test ResetIOmanip objects
#include <iostream>
#include <fstream>
#include "ResetIOmanip.h"

int main () {
    using std::cout;
    using std::endl;

    double randNumb1 = 45.235723;
    double randNumb2 = 1.49;

    ResetIOmanip resetFormats1;
    cout << "Original 1: " << randNumb1 << endl;
    cout << "Original 2: " << randNumb2 << endl;
    cout << "setprecision(4) for #1: " << std::setprecision ( 4 ) << randNumb1 << endl;
    cout << "setprecision(4) for #2: " << std::setprecision ( 4 ) << randNumb2 << endl << endl;

    cout << "setprecision(4) and fixed for #1: " << std::fixed << std::setprecision ( 4 ) << randNumb1 << endl;
    cout << "setprecision(4) and fixed for #2: " << std::fixed << std::setprecision ( 4 ) << randNumb2 << endl;

    cout << "setfill(x) and setw(10) for #1: " << std::setfill ( 'x' ) << std::setw ( 10 ) << randNumb1 << endl;
    cout << "setfill(x) and setw(10) for #2: " << std::setfill ( 'x' ) << std::setw ( 10 ) << randNumb2 << endl << endl;

    cout << "Testing Format #1: " << randNumb1 << endl;
    cout << "Testing Format #2: " << randNumb2 << endl;

    cout << "Testing Format with set width(10) #1: " << std::setw(10) << randNumb1 << endl;
    cout << "Testing Format with set width(10) #2: " << std::setw ( 10 ) << randNumb2 << endl << endl;

    cout << "RESETING - TESTING CLASS" << endl;

    resetFormats1.resetAll ();
    cout << "Testing Format #1: " << randNumb1 << endl;
    cout << "Testing Format #2: " << randNumb2 << endl;

    cout << "Testing Format with set width(10) #1: " << std::setw ( 10 ) << randNumb1 << endl;
    cout << "Testing Format with set width(10) #2: " << std::setw ( 10 ) << randNumb2 << endl << endl;



    cout << "Testing with ostream to testResetIOmanip.txt" << endl;
    std::ofstream testingOut;
    testingOut.open ( "testResetIOmanip.txt", std::ios::out );
    if (testingOut.fail ()) {
        cout << "ERROR: Cannot open the file" << endl;
        return 0;
    }
    ResetIOmanip resetFormats2 ( testingOut );

    testingOut << "Original 1: " << randNumb1 << endl;
    testingOut << "Original 2: " << randNumb2 << endl;
    testingOut << "setprecision(4) for #1: " << std::setprecision ( 4 ) << randNumb1 << endl;
    testingOut << "setprecision(4) for #2: " << std::setprecision ( 4 ) << randNumb2 << endl << endl;

    testingOut << "setprecision(4) and fixed for #1: " << std::fixed << std::setprecision ( 4 ) << randNumb1 << endl;
    testingOut << "setprecision(4) and fixed for #2: " << std::fixed << std::setprecision ( 4 ) << randNumb2 << endl;

    testingOut << "setfill(x) and setw(10) for #1: " << std::setfill ( 'x' ) << std::setw ( 10 ) << randNumb1 << endl;
    testingOut << "setfill(x) and setw(10) for #2: " << std::setfill ( 'x' ) << std::setw ( 10 ) << randNumb2 << endl << endl;

    testingOut << "Testing Format #1: " << randNumb1 << endl;
    testingOut << "Testing Format #2: " << randNumb2 << endl;

    testingOut << "Testing Format with set width(10) #1: " << std::setw ( 10 ) << randNumb1 << endl;
    testingOut << "Testing Format with set width(10) #2: " << std::setw ( 10 ) << randNumb2 << endl << endl;

    testingOut << "RESETING - TESTING CLASS" << endl;
    resetFormats2.resetAll ();

    testingOut << "Testing Format #1: " << randNumb1 << endl;
    testingOut << "Testing Format #2: " << randNumb2 << endl;

    testingOut << "Testing Format with set width(10) #1: " << std::setw ( 10 ) << randNumb1 << endl;
    testingOut << "Testing Format with set width(10) #2: " << std::setw ( 10 ) << randNumb2 << endl << endl;

    testingOut.close ();

    return 0;
}