C++使用move实现vector

• 此处代码值得挖掘
• 可以放到编译器中调试，学习
• 模板、const、引用、、、、
• 好好思考

#include 
#include 
#include 
using namespace std;
class Element {
private:
	int number;
public:
	Element() :number(0) {
		cout << "ctor" << endl;
	}
	Element(int num) :number(num) {
		cout << "ctor" << endl;
	}
	Element(const Element& e) :number(e.number) {    //复制构造函数
		cout << "copy ctor" << endl;
	}
	Element(Element&& e) :number(e.number) {    //右值引用构造函数
		cout << "right value ctor" << endl;
	}
	~Element() {
		cout << "dtor" << endl;
	}
	void operator=(const Element& item) {
		number = item.number;
	}
	bool operator==(const Element& item) {
		return (number == item.number);
	}
	void operator()() {
		cout << number;
	}
	int GetNumber() {
		return number;
	}
};

template
class Vector {
private:
	T * items;
	int count;
public:
	Vector() :count{ 0 }, items{ nullptr } {

	}

	Vector(const Vector& vector) :count{ vector.count } {
		items = static_cast(malloc(sizeof(T) * count));
		memcpy(items, vector.items, sizeof(T) * count);
	}

	Vector(Vector&& vector) :count{ vector.count }, items{ vector.items } {
		//TODO
		vector.count = 0;
		vector.items = nullptr;
	}

	~Vector() {    //调用Clear（）函数，由于Clear（）并不对items析构，且将count置为0，所以不会引发重复析构错误
		//TODO
		Clear();
		delete items;
	}
	T& operator[](int index) {
		if (index < 0 || index >= count) {
			cout << "invalid index" << endl;
			return items[0];
		}
		return items[index];
	}
	int returnCount() {
		return count;
	}
	void Clear(){	//需要调用各个元素的析构函数，但是并不对items析构
		for (int i = 0; i < count; i++)
		{
			items[i].~T();
		}
		items = nullptr;
		count = 0;
	}

	void Add(const T& item) {    //类似STL的Vector.push_back（），但是STL中Vector有预存的内存（capacity），不需要每次添加都重新分配
		                     //详细可以查看 Vector 的 push_back 实现原理
		T *newitems = static_cast(malloc(sizeof(T)*(count + 1)));
		for (int i = 0; i < count; i++)
		{
			new(&newitems[i])T(move(items[i]));    //在新申请的内存构造对象，使用move可以调用对象的右值引用构造函数，提高效率
		}
		new(&newitems[count])T(move(item));
		for (int i = 0; i < count; i++)
		{
			items[i].~T();    //释放原来的对象
		}
		items = newitems;    //保存重新申请的内存地址
		count++;
	}
	bool Insert(const T& item, int index) {
		//插入元素，操作同Add原理
		if (index < 0 || index >count)    //判断参数合法性
		{
			return false;
		}
		T *newitems = static_cast(malloc(sizeof(T)*(count + 1)));
		for (int i = 0; i < index; i++)
		{
			new(&newitems[i])T(move(items[i]));
		}
		new(&newitems[index])T(move(item));
		for (int i = index; i < count; i++)
		{
			new(&newitems[i + 1])T(move(items[i]));
		}
		for (int i = 0; i < count; i++)
		{
			items[i].~T();
		}
		items = newitems;
		count++;
		return true;
	}
	bool Remove(int index) {
		//移除元素，操作同Add原理
		if (index < 0 || index >=count)
		{
			return false;
		}
		T *newitems = static_cast(malloc(sizeof(T)*(count - 1)));
		for (int i = 0; i < index; i++)
		{
			new(&newitems[i])T(move(items[i]));
		}
		for (int i = index; i < count-1; i++)
		{
			new(&newitems[i])T(move(items[i+1]));
		}
		for (int i = 0; i < count; i++)
		{
			items[i].~T();
		}
		items = newitems;
		count--;
		return true;
	}
	int Contains(const T& item) {    //寻找元素，匹配返回索引，不匹配返回-1
		for (int i = 0; i < count; i++)
		{
			if (items[i] == item)
			{
				return i;
			}
		}
		return -1;

	}
};

template
void PrintVector(Vector& v) {    //遍历Vector输出
	int count = v.returnCount();
	for (int i = 0; i < count; i++)
	{
		v[i]();
		cout << " ";
	}
	cout << endl;
}

int main() {    //测试用例
	Vectorv;
	for (int i = 0; i < 4; i++) {
		Element e(i);
		v.Add(e);
	}

	PrintVector(v);
	Element e2(4);

	if (!v.Insert(e2, 10))
	{
		v.Insert(e2, 2);
	}
	PrintVector(v);

	if (!v.Remove(10))
	{
		v.Remove(2);
	}
	PrintVector(v);

	Element e3(1), e4(10);
	cout << v.Contains(e3) << endl;
	cout << v.Contains(e4) << endl;

	Vectorv2(v);

	Vectorv3(move(v2));
	PrintVector(v3);
	v2.Add(e3);

	PrintVector(v2);

	return 0;
}

ctor
copy ctor
dtor
ctor
right value ctor
copy ctor
dtor
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right value ctor
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0 1 2 3 
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1
-1
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1 
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