關於將輸入存儲到字符串中，並使用cout來顯示它

Question

我正在編寫一個程序，它將請求用戶輸入INT，並將其存儲在[10]的數組中。我希望能夠讓用戶選擇DISPLAY選項並查看數組中的所有數據。我只是想不通，這裏是我到目前爲止有：

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

這裏是正在調用的函數上面：

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; 
} 

我相信這將會把用戶輸入到字符串last10withdraws。然後我希望用戶能夠調用此函數：

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

並且這將有望顯示數組的內容。關於我做錯什麼的想法？

Answer 1

last10withdraws[10]; 

這什麼都不做。這需要數組的第11個元素的值（不存在），然後將其丟棄。

同樣這樣的：

last10withdraws[amount]; 

取last10withdraws一個元素的值並拋出它扔掉。它不會爲其分配任何價值或將其存儲在任何地方。

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從您的評論：

首先，你需要在你的saving稱爲像nr_of_withdraws一個額外的變量。它將跟蹤已經制造了多少withdraws。在課程結束時它應該被分配到零。

然後每次插入到last10withdraws時，您都會增加nr_of_withdraws。如果nr_of_withdraws大於9，那麼你的數組已滿，你需要做些什麼。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; 
}