Hello sword4869/learn_cpp

# 1. Normal

To create objects of the template class for different types, specify the data type in angle brackets, as we did when defining the function outside of the class.

#include <iostream>
using namespace std;

template <class T>
class MyClass {
public:
    T first;
    MyClass(T x):first(x){}
    void print1();
    void print2(T y);
};

template <class T>
void MyClass<T>::print1(){
    cout << first << endl;
}

template <class T>
void MyClass<T>::print2(T y){
    cout << y << endl;
}

int main() {
    MyClass<int> m(10);
    m.print1();
    // m.print2("str"); 只能写同样的T
    m.print2(100);
    MyClass<string> n("hello");
    n.print1();
}

模板类中的函数的语法，就是函数模板的语法多了个MyClass<T>::.

# 2. Specialization

Template specialization allows for the definition of a different implementation of a template when a specific type is passed as a template argument.

First of all, notice that we precede the class name with template<>, including an empty parameter list. This is because all types are known and no template arguments are required for this specialization. More important than this prefix, is the <string> specialization parameter after the class template name and the inner part of the class also uses a specific string type.

Keep in mind that there is no member "inheritance" from the generic template to the specialization, so all members of the template class specializations must be defined on their own.

#include <iostream>
using namespace std;

template <class T>
class MyClass {
public:
    T first;
    MyClass(T x):first(x){
        cout << x << " is not string" << endl;
    }
};

template <>
class MyClass<string> {
public:
    string first;
    MyClass(string x):first(x){
        cout << x << " is string" << endl;
    }
};

int main() {
    MyClass<int> m(10);
    MyClass<double> n(3.14);
    MyClass<string> p("hello");
}

# 代码分离

如果需要代码分离，即 template class 的声明、定义，以及 main 函数分属不同文件。例如：

src_dir
|____MyStack.h
|____MyStack.cpp
|____main.cpp

则 main.cpp 文件中需要同时包含 .h 文件和 .cpp 文件，不然会出现链接错误。

// main.cpp
#include "MyStack.h"
#include "MyStack.cpp"

// 其他include
// main函数主体

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