c++ - 接收错误: expression must have pointer-to-class type

Question

我收到错误“表达式必须具有指向类的指针类型”。我已经搜索了错误，但未能找到可以弄清楚发生了什么的帖子。我在第 49 行收到关于 Sequence2.cpp 的错误 (data->resize( capacity * 2 );)

Sequence2.h

typedef double value_type;

    class sequence
    {

    private:
        value_type* data;
        int used;
        int current_index;
        int capacity;

    public:
        // TYPEDEFS and MEMBER CONSTANTS
        static const int DEFAULT_CAPACITY = 5;

        // CONSTRUCTORS and DESTRUCTOR
        sequence(int initial_capacity = DEFAULT_CAPACITY);
        sequence(const sequence& source);
        ~sequence();

        // MODIFICATION MEMBER FUNCTIONS
        void insert(const value_type& entry);
        void resize(int new_capacity);

        // ADDITIONAL FUNCTIONS THAT ARE NOT RELEVANT

Sequence2.cpp

#include "stdafx.h"
#include "Sequence2.h"


//     Postcondition: The sequence has been initialized as an empty sequence.
//     The insert/attach functions will work efficiently (without allocating
//     new memory) until this capacity is reached.

sequence::sequence(int initial_capacity)
{
    capacity = initial_capacity;
    current_index = -1;
    data = new value_type[DEFAULT_CAPACITY];
}

sequence::sequence(const sequence & source)
{
    // NEED TO DO
    // Postcondition: the sequence has made a deep copy of the source sequence.
}

sequence::~sequence()
{
    delete[] data;
}

// Postcondition: A new copy of entry has been inserted in the sequence
// before the current item. If there was no current item, then the new entry 
// has been inserted at the front of the sequence. In either case, the newly
// inserted item is now the current item of the sequence.

void sequence::insert(const value_type & entry)
{
    if (current_index < 0) 
    {
        current_index = 0; // Set current index to first index
        data[current_index] = entry;
        used++;
    }
    else 
    {
        if (used < capacity) {
            data[current_index + 1] = entry;
            current_index++;
            used++;
        }
        else 
        {
            data->resize( capacity * 2 );
        }
    }


}



void sequence::resize(int new_capacity)
{
    value_type *temp = new value_type[capacity];
    int temp_capacity = capacity;

    for (int i = 0; i < capacity; i++)
    {
        temp[i] = data[i];
    }

    delete[] data;

    data = new value_type[new_capacity];

    for (int i = 0; i < temp_capacity; i++)
    {
        data[i] = temp[i];
        used++;
        current_index++;
    }

    delete[] temp;

}

Answer 1

resize 也是一个成员函数，您没有正确调用它。改变

data->resize( capacity * 2 );

到

resize( capacity * 2 );

还有一些其他问题:

1. 您可能需要在 insert() 中调用 resize() 之后插入值。

2. 无需在 resize() 中 new/delete 两次。

3. 在 resize() 之后，used 和 current_index 的值似乎不对。