使用cin与矢量和类 [英] Using cin with vector and class
问题描述
使用vector.push_back函数在类中使用cin的最佳方法是什么？
我知道它是否是正常向量我可以这样做然后使用sentinel代码来提示结束
int myint;
vector< int> Ÿ;
cout<< vector integer<< ENDL;
while （（cin>> myint）&& myint！= 9999 ）
y.push_back（myint）;
for （ int i = 0 ; i < y.size（）; i ++）
cout<< y =<< y [i]<<这是我的代码：
#include< iostream>
#include< fstream>
#include< vector>
using namespace std;
类账户{
protected：
int accno;
双倍余额;
public：
Account（int accno，double balance）：accno（accno），balance（balance）{};
double getBalance（）{return balance;}
void setBalance（double balance）{this-> balance = balance; }
int getAccno（）{return accno;}
void setAccno（int accno）{this-> accno = accno; }
无效存款（双倍金额）{
余额=余额+金额;
}
};
class保存：公共账户{
public：
Saving（）：Account（accno，balance）{};
Saving（int accno，double balance）：Account（accno，balance）{};
bool withdraw（double amount）{
if（balance< amount）{
cout<< 不充足的资金;
返回false;
}
else {
余额=余额 - 金额;
返回true;
}
}
void compute_interest（）{
balance = balance * 1.05;
}
void print（）{
cout<< ID：<< accno<< balance：<<余额<< ENDL;
}
朋友istream&运算符>>（istream& input，Saving& account）{
cout<< ID： ;
输入>> account.accno;
cout<< 平衡：;
输入>>账户余额;
返回输入;
}
朋友ostream&运算符<<（ostream& output，const Saving& account）{
output<< ID：<< account.accno<< balance：<< account.balance<< ENDL;
}
//朋友布尔运算符！=（保存a，int b）
};
int main（）
{
保存储蓄[5];
cout<< 保存数组<< ENDL;
for（int i = 0; i< 5; i ++）{
cin>>节省[I];
saving [i] .print（）;
cout<< ENDL;
}
保存myvec;
vector< Saving> savingV;
cout<< 保存矢量<< ENDL;
while（（cin>> myvec）&&（myvec.getAccno（）！= 9999））{
int i = 0;
savingV.push_back（myvec）;
savingV [i] .print（）;
cout<< ENDL;
i ++;
}
返回0;
}
正如您在主要功能中看到的那样，我首先使用数组进行测试。
基本上我真正想做的事情使用cin with class（vector not array）是为了保持插入值，直到提示sentinel值或字符或字符串。
&我仍然无法设计运算符重载函数（比如！=）
这就是我想通过重载！=运算符来做的事情
while（（cin>> myvec）&& myvec！= 9999）;
但是idk是否可以完成。
我尝试过：
do {
int i = 0;
cin>> myvec;
savingV.push_back（myvec）;
savingV [i] .print（）;
cout<< endl;
i ++;
} while（cin>> myvec&&（（myvec.getAccno（）！= 9999）||（myvec.getBalance （）！= 9999）））;
解决方案
你基本上有正确的想法。你可以写一个规范的运算符！= as：
bool operator ！=（保存const& lhs，保存const& rhs）
{
// 详细信息省略
}
然后声明一个sentinel值（例如 Saving sentinel（9999，-1.0）），或者你可以编写一个运算符，将 Saving 与 int 进行比较（或者任何其他类型）：
bool operator ！=（保存const& lhs， int rhs）
{
// 详细信息省略
}
任何一种方法都应该有效。
请注意，如果您声明 operator！= ，最好同时声明 operator ==
What are the best ways to use cin with class using vector.push_back function?
I know if it's normal vector I can do it like this and then use a sentinel code to prompt the end
int myint;
vector<int> y;
cout << "vector integer" << endl;
while ((cin >> myint) && myint != 9999)
y.push_back(myint);
for (int i = 0; i < y.size(); i++)
cout << "y = " << y[i] << endl;*
Here's my code:
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
class Account{
protected:
int accno;
double balance;
public:
Account(int accno, double balance) : accno(accno), balance(balance){};
double getBalance() {return balance;}
void setBalance(double balance){ this->balance=balance; }
int getAccno() {return accno;}
void setAccno(int accno){ this->accno=accno; }
void deposit(double amount){
balance = balance + amount;
}
};
class Saving : public Account{
public:
Saving () : Account(accno,balance){};
Saving (int accno, double balance) : Account(accno,balance){};
bool withdraw (double amount){
if (balance < amount){
cout << "Insufficient funds";
return false;
}
else{
balance = balance - amount;
return true;
}
}
void compute_interest(){
balance = balance * 1.05;
}
void print(){
cout << "ID: " << accno << " balance: " << balance << endl;
}
friend istream& operator >>(istream& input, Saving& account){
cout << "ID: ";
input >> account.accno;
cout << "balance: ";
input >> account.balance;
return input;
}
friend ostream& operator <<(ostream& output, const Saving& account){
output << "ID: " << account.accno << " balance: " << account.balance << endl;
}
//friend bool operator !=(Saving a, int b)
};
int main()
{
Saving saving[5];
cout << "saving array" << endl;
for (int i = 0; i < 5; i++){
cin >> saving[i];
saving[i].print();
cout << endl;
}
Saving myvec;
vector<Saving> savingV;
cout << "saving vector" << endl;
while ((cin >> myvec) && (myvec.getAccno() != 9999)){
int i = 0;
savingV.push_back(myvec);
savingV[i].print();
cout << endl;
i++;
}
return 0;
}
As you can see in the main function i tested first using an array.
Basically what I really want to do using cin with class(vector not array) is to keep inserting value until a sentinel value or character or string is prompted.
& I'm still having trouble designing operator overloading functions (like the !=)
This is what I thought of doing by overloading the "!=" operator
while ((cin >> myvec) && myvec != 9999);
But idk whether it can be done.
What I have tried:
do{
int i = 0;
cin >> myvec;
savingV.push_back(myvec);
savingV[i].print();
cout << endl;
i++;
} while (cin >> myvec && ((myvec.getAccno() != 9999) || (myvec.getBalance() != 9999)));
解决方案 You basically have the correct idea. You can either write a "canonical" operator != as:
bool operator !=(Saving const& lhs, Saving const& rhs)
{
// details omitted
}
and then declare a sentinel value (e.g. Saving sentinel(9999, -1.0)), or you can write an operator that compares Saving to int (or any other type):
bool operator !=(Saving const& lhs, int rhs)
{
// details omitted
}
Either method should work.
Note that if you declare operator !=, it is a good practice to also declare operator ==
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