C++模板

要点

• 模板函数在类的外部定义
• 友元函数在类的外部定义（<<的重载）
• 模板类中静态变量的使用规则

示例

Array.h

#pragma once
#include<iostream>
using namespace std;
template<typename T>
class Array
{
private:
    int len;
    T *data;
    friend ostream& operator<<<T>(ostream &out, Array<T>& array);

public:
    static int x;
    static T y;
    Array(int len);
    ~Array();
    int getLen();
    T* getData();
    T& operator[] (int index);
    Array<T>& operator=(Array<T>& array);
    Array(Array<T>& array);
};

Array.cpp

#include "stdafx.h"
#include "Array.h"
#include<iostream>
using namespace std;
template<typename T>
Array<T>::Array(int len)
{
    this->len = len;
    if(len>0)
        this->data = new T[len];
    else{
        this->data = NULL;
    }
}

template<typename T>
Array<T>::~Array()
{
    if (this->data != NULL) {
        delete []this->data;
    }
}

template<typename T>
int Array<T>::getLen()
{
    return this->len;
}

template<typename T>
T * Array<T>::getData()
{
    return this->data;
}

template<typename T>
T& Array<T>::operator[](int index)
{
    return this->data[index];
}

template<typename T>
Array<T> & Array<T>::operator=(Array<T>& array)
{
    cout << "执行=运算" << endl;
    if (this->data != NULL) {
        delete[]this->data;
    }
    this->len = array.getLen();
    this->data = new T[len];
    for (int i = 0; i < len; i++) {
        this->data[i] = array[i];
    }
    return *this;
}

template<typename T>
Array<T>::Array(Array<T>& array)
{
    cout << "执行copy构造函数" << endl;
    this->len = array.getLen();
    this->data = new T[this->len];
    for (int i = 0; i < this->len; i++) {
        this->data[i] = array[i];
    }
}

template<typename T>
ostream& operator<<(ostream &out, Array<T>& array) {
    for (int i = 0; i < array.len; i++) {
        out << array[i]<<" ";
    }
    out << endl;
    return out;
}
template<typename T>
int Array<T>::x = 10;

template<typename T>
T Array<T>::y;

test.cpp

// ArrayDemo.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "Array.cpp"
#include "iostream"
using namespace std;
int main()
{
    Array<int> array(2);
    array[0] = 1;
    array[1] = 2;
    cout <<"array =>"<< array;
    Array<int> array1 = array;
    cout << "array1=>" << array1;
    Array<int> array2(3);
    array2[0] = 10;
    array2[1] = 20;
    array2[2] = 30;
    cout << "array2=>" << array2 ;
    array2 = array;
    cout << "array2=>" << array2;
    cout << "Array<int>::x  =>" << Array<int>::x << endl;
    Array<int>::x = 100;
    Array<char>::x = 1;
    cout << "Array<int>::x  =>"<<Array<int>::x << endl;
    cout <<"Array<char>::x =>"<< Array<char>::x << endl;
    Array<float>::y = 1000;
    cout << Array<float>::y << endl;
    return 0;
}

运行结果：

运行结果