为什么我在 C++ 的模板中收到所有这些错误？

Question

Here is the list of errors

Errors:

 ||=== Build file: "no target" in "no project" (compiler: unknown) ===|
  F:\C Programs\TemplateClass.cpp|39|error: invalid use of non-static data member 'arraylist<x>::cap'| F:\C
  Programs\TemplateClass.cpp|11|note: declared here| F:\C
  Programs\TemplateClass.cpp||In instantiation of 'void arraylist<x>::fill() [with x = int]':| F:\C
  Programs\TemplateClass.cpp|65|required from here| F:\C
  Programs\TemplateClass.cpp|29|error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'int*')| c:\mingw\lib\gcc\mingw32\9.2.0\include\c++\istream|168|note:
  candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]' <near match>| c:\mingw\lib\gcc\mingw32\9.2.0\include\c++\istream|168|note:  
  conversion of argument 1 would be ill-formed:| F:\C
  Programs\TemplateClass.cpp|29|error: cannot bind non-const lvalue reference of type 'bool&' to an rvalue of type 'bool'

//code

#include <iostream>
using namespace std;
#include <conio.h>

template <class x>
class arraylist {
private:
    x* ptr;
    int cap, I;

public:
    arraylist(int cap)
    {
        ptr = new x[cap];
    }
    arraylist() //default constructor
    {
    }

    void fill()
    {
        cout << "Enter " << cap << " Elements :-\n";

        for (i = 0; i < cap; i++) {
            cout << "Enter " << i + 1 << " Element : ";
            cin >> ptr + i;
            cout << endl;
        }
    }

    void replace(int index, x value) //error message
    {
        *(ptr) + index = value;
    }

    void popdata(int index = cap - 1) //error message
    {
        delete (ptr + index);
    }

    void showdata(int index)
    {
        cout << "The data at index " << index << " is " << *(ptr + index);
    }

    void showlist()
    {

        for (i = 0; i < cap; i++) {
            cout << ptr + i << endl;
        }
    }
};

int main()
{
    arraylist<int> a1;

    a1 = 10;
    a1.fill();
    a1.showlist();
    a1.replace(2, 87);
    a1.showlist();
    a1.popdata(9);
    a1.showlist();
    getch();

    return 1;
}

Answer 1

First stop using this:

#include <conio.h>

The only reason you have it is so that you can use:

getch();

You can change that to ask for use input that will have the same affect:

#include <iostream>
...

std::cout << "Please hit return to exit application\n";
std::cin.get();

---

Please stop using this:

using namespace std;

Yes I know have to add std:: in-front of a couple of things but in the long run this will make your life easier.

---

Bugs:

 // You have not specified the type of i
 for (i = 0; i < cap; i++) {

All variables in C++ need a type. Add a type like this:

 // Note: There are two places to fix this.
 for (int i = 0; i < cap; i++) {

---

Your syntax fo accessing members of the array is slightly off:

 cin >> ptr + i;
 ...
 *(ptr) + index = value;

Change these to:

cin >> ptr[i];
...
ptr[index] = value;

---

void popdata(int index = cap - 1)
                      ^^^^^^^^^^ this part is not valid
                                 outside the class (where this is being called)
                                 you don't have accesses to the members.

To make it work get rid of that part for now.

void popdata(int index)