C# Learning Diary 30---Generic classes, generic methods, generic delegates

Generics allow you to defer writing the specification of a data type for a programming element within a class or method until it is actually used in your program. In other words, when declaring a class or method, because we don’t know what type of parameters the user wants to pass in, we “dig a hole (“＜Ｔ＞”)” where the type is passed in. When we use it, we Fill it in with specific data types.

Generic class:

Based on the knowledge we learned earlier, we define a class:

　class Data
          {
              public int  n_data;
           }

At this time, the data type of n_data has been determined to be the int type , so when assigning a value to it, it can only be of int type. If it is rewritten as the following generic class:

　

　class Data<T>
             {
               public T n_data;
             }

At this time, the data type of n_data is not yet sure what type it is, so it is When he assigns a value, he needs to specify T, which is the type of n_data, that is, to fill in the pit,

　

　Data<int> data = new Data<int>();    //指定Ｔ为int
　　Data<string> data = new Data<string>();  //指定Ｔ为string

Of course, in the above example, T cannot be specified as an array. If you want to If the type of n_data is an array, the following example can be satisfied:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
  
namespace Example  
{  
    class Data<T> //泛型类  
    {  
        public T[] n_data; //泛型变量  
       public Data(int size) //构造方法,new的时候调用构造方法开辟空间  
        {   
          n_data = new T[size];    
        }  
        //输入  
       public void setdata(int index,T value)  
       {  
           n_data[index] = value;  
       }  
        //输出  
       public T getdata(int x)  
       {   
          return n_data[x];  
       }  
    }  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            Data<int> data = new Data<int>(5);  
            data.n_data[2] = 2;  
           Console.WriteLine(data.n_data[2]);  
        }  
    }  
}

The result is: 2

Generic method:

We take the swap exchange method as an example. The swap function in C++ is written like this:

#include <iostream>  
  
using namespace std;  
template <typename T>  
void swap1(T &a,T &b)　//也可以看作泛型  
{  
  T temp;  
  temp = a;  
  a = b;  
  b = temp;  
}  
int main()  
{  
    int a=0,b=1;  
    swap1(a,b);  
    cout<<a<<"\t"<<b<<endl;  
 　　　　　return 0;  
}

Result: 1　0
If a and b are character types, the above functions are also applicable. The C# swap method is as follows:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
  
namespace Example  
{  
    class data  
    {//swap方法，ref是按地址传递  
        public static void swap<T>(ref T a, ref T b)  
        {  
            T temp;  
            temp = a;  
            a = b;  
            b = temp;  
        }  
        static void Main(string[] args)  
        {  
            string a = "HC";  
            string b = "666";  
            swap(ref a,ref b);  
            Console.WriteLine(a+"\t"+b); //结果 666    HC  
        }  
    }  
}

Result: 666 HC This is very similar to C++

Generic delegate:

There are also generic delegates Type, continue the above example:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
  
namespace Example  
{  
    public delegate void MyDelegate<T>();//泛型委托  
    class Data<T>  
    {  
        private T a;  
        private T b;  
        public void setvalue(T x, T y)  
        {  
            a = x;  
            b = y;  
        }  
        //swap方法，ref是按地址传递  
        public void swap()  
        {  
            T temp;  
            temp = a;  
            a = b;  
            b = temp;  
        }  
        public void printvalue()  
        {  
            Console.WriteLine(a + "\t" + b);  
  
        }  
  }  
      class program  
       {   
         static void Main(string[] args)  
          {  
            Data<string> data = new Data<string>();  
            data.setvalue("HC","666");  
            MyDelegate<string> my = new MyDelegate<string>(data.swap);  
            my += data.printvalue;  
            my();  //结果　６６６　　ＨＣ        
           }  
          
       }  
        
   }

Result:

## We have introduced so much about generics, what are the mistakes? Welcome Point out ^_^

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