关于将输入存储到字符串中，并使用cout来显示它

Question

我正在编写一个程序，它将请求用户输入INT，并将其存储在[10]的数组中。我希望能够让用户选择DISPLAY选项并查看数组中的所有数据。我只是想不通，这里是我到目前为止有：

case 2 : { 
       int SamtW; 
       cout << " Please enter how much you would like to withdraw "<< endl; 
       cin >> SamtW; 
       sa.doWithdraw(SamtW); 
       break; 
      } 

这里是正在调用的函数上面：

int saving:: doWithdraw(int amount) 
{ 
    for (int i = 0; i < 10; i++) 
{ 
    last10withdraws[amount]; 
    } 
    if (amount > 1) 
    { 
    setBalanceW(amount); 
    } 
    else { 
     cout << " ERROR. Number must be greater then zero. " << endl; 
    } 
    return 0; 
} 

我相信这将会把用户输入到字符串last10withdraws。然后我希望用户能够调用此函数：

string saving::display() 
{ 
    last10withdraws[10]; 
    return 0; 
} 

并且这将有望显示数组的内容。关于我做错什么的想法？

Answer 1

last10withdraws[10]; 

这什么都不做。这需要数组的第11个元素的值（不存在），然后将其丢弃。

同样这样的：

last10withdraws[amount]; 

取last10withdraws一个元素的值并抛出它扔掉。它不会为其分配任何价值或将其存储在任何地方。

我想你想：

int saving:: doWithdraw(int amount) 
{ 
    if (amount > 0) 
    { 
     for (int i = 9; i != 0; i--) 
     { // move the 9 elements we're keeping up one 
      last10withdraws[i] = last10withdraws[i-1]; 
     } 
     last10withdraws[0] = amount; // add the latest 
     setBalanceW(amount); // process the withdraw 
    } 
    else 
    { 
     cout << " ERROR. Number must be greater then zero. " << endl; 
    } 
    return 0; 
} 

Answer 2

OK从您的评论：

首先，你需要在你的saving称为像nr_of_withdraws一个额外的变量。它将跟踪已经制造了多少withdraws。在课程结束时它应该被分配到零。

然后每次插入到last10withdraws时，您都会增加nr_of_withdraws。如果nr_of_withdraws大于9，那么你的数组已满，你需要做些什么。所以......

---

// Constructor. 
saving::saving { 
    nr_of_withdraws = 0; 
} 

---

// doWithdraw 
int saving:: doWithdraw(int amount) 
{ 
    // See if you have space 
    if(nr_of_withdraws > 9) 
     cout << "last10withdraws are done. Slow down." 
     return 0; 
    } 
    // These lines. oh thy are needed. 
    last10withdraws[nr_of_withdraws] = amount; 
    nr_of_withdraws++; 

    if (amount > 1) 
    { 
     setBalanceW(amount); 
    } 
    else { 
     cout << " ERROR. Number must be greater then zero. " << endl; 
    } 
    return 0; 
}