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将C风格字符串用作string对象引用参数

椰果玩安卓 2022-01-04 阅读 48
C++
// strquote.cpp  -- different designs
#include <iostream>
#include <string>
using namespace std;
string version1(const string& s1, const string& s2);
const string& version2(string& s1, const string& s2);  // has side effect
const string& version3(string& s1, const string& s2);  // bad design

int main()
{
    string input;
    string copy;
    string result;

    cout << "Enter a string: ";
    getline(cin, input);
    copy = input;
    cout << "Your string as entered: " << input << endl;
    result = version1(input, "***");
    cout << "Your string enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;

    result = version2(input, "###");
    cout << "Your string enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;

    cout << "Resetting original string.\n";
    input = copy;
    result = version3(input, "@@@");
    cout << "Your string enhanced: " << result << endl;
    cout << "Your original string: " << input << endl;
    // cin.get();
    // cin.get();
    return 0;
}

string version1(const string& s1, const string& s2)
{
    string temp;

    temp = s2 + s1 + s2;
    return temp;
}

const string& version2(string& s1, const string& s2)   // has side effect
{
    s1 = s2 + s1 + s2;
    // safe to return reference passed to function
    return s1;
}

const string& version3(string& s1, const string& s2)   // bad design
{
    string temp;

    temp = s2 + s1 + s2;
    // unsafe to return reference to local variable
    return temp;
}

 

 

 

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