C # Learning diary 30 --- generic classes, generic methods, generic delegation

C # Learning diary 30 --- generic classes, generic methods, generic delegation

Generics allow you to delay writing the data type specification of the programming element in a class or method until it is actually used in a program. In other words, when declaring a class or method, because you do not know what type of parameters you want to input, "dig a hole (" <T> ")" in the input type ")", when using it, we can fill in it with specific data types.

Generic Type:

Based on the previous knowledge, we define a class:

Class Data

{

Public int n_data;

}

At this time, the Data Type of n_data has been determined to be int type. Therefore, when assigning values to n_data, it can only be int type. If it is changed to the following generic class:

Class Data

{

Public T n_data;

}

At this time, the Data Type of n_data is not determined. Therefore, when assigning values to it, you need to specify T, that is, the type of n_data, that is, fill in,

Data Data = new Data (); // Specify T as int

Data Data = new Data (); // Specify T as string

Of course, T cannot be specified as an array in the above example. If the n_data type is to be set to an array, the following example can meet the following requirements:

Using System; using System. Collections. Generic; using System. Linq; using System. Text; namespace Example {class Data
 
  
// Generic class {public T [] n_data; // The generic variable public Data (int size) // constructor, when new, call the constructor to open up space {n_data = new T [size];} // enter public void setdata (int index, T value) {n_data [index] = value ;} // output public T getdata (int x) {return n_data [x] ;}} class Program {static void Main (string [] args) {Data
  
   
Data = new Data
   
    
(5); data. n_data [2] = 2; Console. WriteLine (data. n_data [2]) ;}}
   
  
 

Result: 2

Generic method:

In this example, we use the swap switching method. In C ++, the swap function is written as follows:

# Include
 
  
Using namespace std; template
  
   
Void swap1 (T & a, T & B) // It can also be considered as a generic {T temp; temp = a; a = B; B = temp;} int main () {int a = 0, B = 1; swap1 (a, B); cout <
   
Result: 1 0. If a and B are character types and above, they are also applicable. C # swap method:
   
Using System; using System. Collections. Generic; using System. Linq; using System. Text; namespace Example {class data {// swap method, ref is the public static void swap passed by address
    
     
(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 ++ B); // result 666 HC }}}
    
   

Result: 666 HC is similar to C ++.
   
 
Generic delegation:
   
The delegation also has a generic type, and the above example is as follows:
   
Using System; using System. Collections. Generic; using System. Linq; using System. Text; namespace Example {public delegate void MyDelegate
    
     
(); // Generic delegate class Data
     
      
{Private T a; private T B; public void setvalue (T x, T y) {a = x; B = y ;}// swap method, ref is the public void swap () {T temp; temp = a; a = B; B = temp;} public void printvalue () {Console. writeLine (a ++ B) ;}} class program {static void Main (string [] args) {Data
      
       
Data = new Data
       
        
(); Data. setvalue (HC, 666); MyDelegate
        
         
My = new MyDelegate
         
           (Data. swap); my + = data. printvalue; my (); // The result is 666 HC }}}
         
        
       
      
     
    
   

Result:
   

   
 
   
 
   
There are so many introductions about generics, and you are welcome to point out the errors. ^_^