1 DynamicArray设计要点

类模板

• 动态确定内部数组空间的大小
• 实现函数返回数组长度
• 构造拷贝和赋值操作

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2 继承关系图和接口实现

继承关系图

接口实现

template < typename T >
class DynamicArray : public Array<T>
{
protected:int m_length;public:DynamicArray(int length);DynamicArray(const DynamicArray<T>& obj);DynamicArray<T>& operator= (const DynamicArray<T>& obj);void resize(int length);int length() const;~DynamicArray();
};

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3 代码实现

DynamicArray.h

#ifndef DYNAMICARRAY_H
#define DYNAMICARRAY_H#include "Array.h"
#include "Exception.h"namespace LemonLib {
template < typename T >
class DynamicArray : public Array<T>
{
protected:int m_length;public:DynamicArray(int length = 0){this->m_array = new T[length];if (this->m_array){m_length = length;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to create DynamicArray obj...");}}DynamicArray(const DynamicArray<T>& obj){this->m_array = new T[obj.m_length];if (this->m_array){for (int i=0; i<obj.m_length; i++){this->m_array[i] = obj.m_array[i];}m_length = obj.m_length;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to copy DynamicArray obj...");}}DynamicArray<T>& operator= (const DynamicArray<T>& obj){if (this != &obj){T* array = new T[obj.m_length];if (array){for (int i=0; i<obj.m_length; i++){array[i] = obj.m_array[i];}T* tmp = this->m_array;this->m_array = array;m_length = obj.m_length;delete[] tmp;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to copy DynamicArray obj...");}}return *this;}void resize(int length){if (length != m_length){T* array = new T[length];if (array){int len = (m_length < length) ? m_length : length;for (int i=0; i<len; i++){array[i] = this->m_array[i];}T* tmp = this->m_array;this->m_array = array;m_length = length;delete[] tmp;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to resize DynamicArray obj...");}}}int length() const{return m_length;}~DynamicArray(){delete[] this->m_array;}
};
}#endif // DYNAMICARRAY_H

main.cpp

#include <iostream>
#include "Object.h"
#include "Exception.h"
#include "List.h"
#include "Seqlist.h"
#include "Staticlist.h"
#include "Dynamiclist.h"
#include "Staticarray.h"
#include "DynamicArray.h"using namespace std;
using namespace LemonLib;int main()
{DynamicArray<int> da(5);for (int i=0; i<da.length(); i++){da[i] = i * i;}for (int i=0; i<da.length(); i++){cout << da[i] << endl;}DynamicArray<int> da1 = da;for (int i=0; i<da1.length(); i++){cout << da[i] << endl;}DynamicArray<int> da2(10);da2 = da1;for (int i=0; i<da2.length(); i++){cout << da2[i] << endl;}da2.resize(10);for (int i=0; i<da2.length(); i++){cout << da2[i] << endl;}da2.resize(3);for (int i=0; i<da2.length(); i++){cout << da2[i] << endl;}return 0;
}

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4 代码优化

可以看出DynamicArray类中函数实现存在重复的逻辑，如何进行代码优化呢？

重复代码逻辑的抽象

• init：对象构造时的初始化操作。
• copy：在堆空间中申请新的内存，并执行拷贝操作。
• update：将指定的堆空间作为内部存储数组使用。

#ifndef DYNAMICARRAY_H
#define DYNAMICARRAY_H#include "Array.h"
#include "Exception.h"namespace LemonLib {
template < typename T >
class DynamicArray : public Array<T>
{
protected:int m_length;T* copy(T* array, int len, int newLen){T* ret = new T[newLen];if (ret != NULL){int size = (len < newLen) ? len : newLen;for (int i=0; i<size; i++){ret[i] = array[i];}}return ret;}void update(T* array, int len){if (array != NULL){T* tmp = this->m_array;this->m_array = array;m_length = len;delete[] tmp;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to update DynamicArray obj...");}}void init(T* array, int len){if (array != NULL){this->m_array = array;m_length = len;}else{THROW_EXCEPTION(NoEnoughMemoryException, "No enough memory to init DynamicArray obj...");}}public:DynamicArray(int length){init(new T[length], length);}DynamicArray(const DynamicArray<T>& obj){init(copy(obj.m_array, obj.m_length, obj.m_length), obj.m_length);}DynamicArray<T>& operator= (const DynamicArray<T>& obj){if (this != &obj){update(copy(obj.m_array, obj.m_length, obj.m_length), obj.m_length);}return *this;}void resize(int length){if (length != m_length){update(copy(this->m_array, m_length, length), length);}}int length() const{return m_length;}~DynamicArray(){delete[] this->m_array;}
};
}#endif // DYNAMICARRAY_H