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第二十课数组类的创建（下）

在创建StaticArray时，数组的大小必须是明确指定的，我们需要创建一个新的数组类，数组的大小可以动态的指定。

课程目标：

实验：

新建文件DynamicArray.h文件，如下：

  1 #ifndef DYNAMICARRAY_H
  2 #define DYNAMICARRAY_H
  3 
  4 #include "Array.h"
  5 #include "Exception.h"
  6 
  7 namespace DTLib
  8 {
  9 
 10 template < typename T >
 11 class DynamicArray : public Array<T>
 12 {
 13 protected:
 14     int m_length;
 15 public:
 16     DynamicArray(int length)
 17     {
 18         this->m_array = new T[length];
 19 
 20         if(this->m_array != NULL)
 21         {
 22             this->m_length = length;
 23         }
 24         else
 25         {
 26             THROW_EXCEPTION(NoEnoughMemoryException, "No memory to create DynamicArray Object...");
 27         }
 28     }
 29 
 30     DynamicArray(const DynamicArray<T>& obj)
 31     {
 32         this->m_array = new T[obj.m_length];
 33 
 34         if(this->m_array != NULL)
 35         {
 36             this->m_length = obj.m_length;
 37 
 38             for(int i=0; i<obj.m_length; i++)
 39             {
 40                 this->m_array[i] = obj.m_array[i];
 41             }
 42         }
 43         else
 44         {
 45             THROW_EXCEPTION(NoEnoughMemoryException, "No memory to create DynamicArray Object...");
 46         }
 47     }
 48 
 49     DynamicArray<T>& operator= (const DynamicArray<T>& obj)
 50     {
 51         if( this != &obj )
 52         {
 53             T* array = new T[obj.m_length];
 54 
 55             if( array != NULL )
 56             {
 57                 for(int i=0; i<obj.m_length; i++)
 58                 {
 59                     array[i] = obj.m_array[i];
 60                 }
 61 
 62                 T* temp = this->m_array;
 63 
 64                 this->m_array = array;
 65                 this->m_length = obj.length;
 66 
 67                 delete[] temp;     //先保存原来的指针，赋值新指针成功再释放原来的，保证异常安全
 68             }
 69             else
 70             {
 71                 THROW_EXCEPTION(NoEnoughMemoryException, "No memory to copy Object...");
 72             }
 73         }
 74     }
 75 
 76     int length() const
 77     {
 78         return m_length;
 79     }
 80 
 81     void resize(int length)     //动态重置数组的长度
 82     {
 83         if( length != m_length)
 84         {
 85             T* array = new T[length];
 86 
 87             if( array != NULL )
 88             {
 89                 int size = (length < m_length) ? length : m_length;
 90 
 91                 for(int i=0; i<size; i++)
 92                 {
 93                     array[i] = this->m_array[i];
 94                 }
 95 
 96                 T* temp = this->m_array;
 97 
 98                 this->m_array = array;
 99                 this->m_length = length;
100 
101                 delete[] temp;
102             }
103             else
104             {
105                 THROW_EXCEPTION(NoEnoughMemoryException, "No memory to resize Object...");
106             }
107         }
108     }
109 
110     ~DynamicArray()
111     {
112         delete[] this->m_array;
113     }
114 };
115 
116 }
117 
118 #endif // DYNAMICARRAY_H

测试程序如下：

#include <iostream>
#include "DynamicArray.h"


using namespace std;
using namespace DTLib;


int main()
{

    DynamicArray<int> s1(5);

    for(int i = 0; i<s1.length(); i++)
    {
        s1[i] = i * i;
    }

    for(int i = 0; i < s1.length(); i++)
    {
        cout << s1[i] << endl;
    }

    return 0;
}

结果如下：

第二个测试程序：

 1 #include <iostream>
 2 #include "DynamicArray.h"
 3 
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 
 9 int main()
10 {
11 
12     DynamicArray<int> s1(5);
13 
14     for(int i = 0; i<s1.length(); i++)
15     {
16         s1[i] = i * i;
17     }
18 
19     for(int i = 0; i < s1.length(); i++)
20     {
21         cout << s1[i] << endl;
22     }
23 
24     DynamicArray<int> s2(10);
25 
26     s2 = s1;
27 
28     for(int i = 0; i < s2.length(); i++)
29     {
30         cout << s2[i] << endl;
31     }
32 
33 
34 
35     return 0;
36 }

结果如下：

可以看到赋值之后，s2就只有5个元素了。

第三个测试程序：

 1 #include <iostream>
 2 #include "DynamicArray.h"
 3 
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 
 9 int main()
10 {
11 
12     DynamicArray<int> s1(5);
13 
14     for(int i = 0; i<s1.length(); i++)
15     {
16         s1[i] = i * i;
17     }
18 
19     for(int i = 0; i < s1.length(); i++)
20     {
21         cout << s1[i] << endl;
22     }
23 
24     DynamicArray<int> s2(10);
25 
26     s2 = s1;
27 
28     s2.resize(3);
29 
30     for(int i = 0; i < s2.length(); i++)
31     {
32         cout << s2[i] << endl;
33     }
34 
35     s2[4] = 5;
36 
37 
38     return 0;
39 }

结果如下：

问题：

重构后的DynamicArray.h如下：

  1 #ifndef DYNAMICARRAY_H
  2 #define DYNAMICARRAY_H
  3 
  4 #include "Array.h"
  5 #include "Exception.h"
  6 
  7 namespace DTLib
  8 {
  9 
 10 template < typename T >
 11 class DynamicArray : public Array<T>
 12 {
 13 protected:
 14     int m_length;
 15 
 16     T* copy(T* array, int len, int newLen)
 17     {
 18         T* ret = new T[newLen];
 19 
 20         if( ret != NULL )
 21         {
 22             int size = (len < newLen) ? len : newLen;
 23 
 24             for(int i=0; i<size; i++)
 25             {
 26                 ret[i] = array[i];
 27             }
 28         }
 29 
 30         return ret;
 31     }
 32 
 33     void update(T* array, int length)
 34     {
 35         if( array != NULL )
 36         {
 37             T* temp = this->m_array;
 38 
 39             this->m_array = array;
 40             this->m_length = length;
 41 
 42             delete[] temp;
 43         }
 44         else
 45         {
 46             THROW_EXCEPTION(NoEnoughMemoryException, "No memory to update DynamicArray Object...");
 47         }
 48     }
 49 
 50     void init(T* array, int length)
 51     {
 52         if( array != NULL )
 53         {
 54             this->m_array = array;
 55             this->m_length = length;
 56         }
 57         else
 58         {
 59             THROW_EXCEPTION(NoEnoughMemoryException, "No memory to create DynamicArray Object...");
 60         }
 61     }
 62 
 63 public:
 64     DynamicArray(int length)
 65     {
 66         init(new T[length], length);
 67     }
 68 
 69     DynamicArray(const DynamicArray<T>& obj)
 70     {
 71         init(copy(obj.m_array, obj.m_length, obj.m_length), obj.m_length);
 72     }
 73 
 74     DynamicArray<T>& operator= (const DynamicArray<T>& obj)
 75     {
 76         if( this != &obj )
 77         {
 78             update(copy(obj.m_array, obj.m_length, obj.m_length), obj.m_length);
 79         }
 80 
 81         return *this;
 82     }
 83 
 84     int length() const
 85     {
 86         return m_length;
 87     }
 88 
 89     void resize(int length)     //动态重置数组的长度
 90     {
 91         if( length != m_length)
 92         {
 93            update(copy(this->m_array, m_length, length), length);
 94         }
 95     }
 96 
 97     ~DynamicArray()
 98     {
 99         delete[] this->m_array;
100     }
101 };
102 
103 }
104 
105 #endif // DYNAMICARRAY_H

测试程序如下：

 1 #include <iostream>
 2 #include "DynamicArray.h"
 3 
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 
 9 int main()
10 {
11 
12     DynamicArray<int> s1(5);
13 
14     for(int i = 0; i<s1.length(); i++)
15     {
16         s1[i] = i * i;
17     }
18 
19     for(int i = 0; i < s1.length(); i++)
20     {
21         cout << s1[i] << endl;
22     }
23 
24     DynamicArray<int> s2(10);
25 
26     s2 = s1;
27 
28     s2.resize(3);
29 
30     for(int i = 0; i < s2.length(); i++)
31     {
32         cout << s2[i] << endl;
33     }
34 
35     return 0;
36 }

结果如下：

小结：

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原文地址：https://www.cnblogs.com/wanmeishenghuo/p/9637539.html

第二十课 数组类的创建（下）

第二十课数组类的创建（下）