[Unity | C #] Basics (10) - Generic (Generic) / generic constraints (where)

[Learning materials]

        > Documents Online

            The official document: https://docs.microsoft.com/zh-cn/dotnet/csharp/

            Rookie Tutorial (Advanced Tutorial) : https://www.runoob.com/csharp/csharp-tutorial.html

        > Video Tutorial

            Tencent college, Siki College

        > Books 

　　　　"C # graphic tutorials" (Chapter 17) : https://www.cnblogs.com/moonache/p/7687551.html

 

【Learning Content】 

　　> Rookie Tutorial: Advanced Tutorial section (generic)

　　> "C # graphic tutorials" (Chapter 17)

 

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【notes】

• definition
  • And in C ++ template template <T> as
  • Generic type can be used: class, structure, interfaces, delegates, the method
  • NOTE: Generic not only a T, can define multiple generic T1, T2, T3 ...

 

•  Generic class (class)
  • Unknown type T , when you create an object determined to avoid overloading more MyList

  • // type T is determined at object creation
     public  class of MyList <T> 
    { 
        Private  int size = 10 ;
         public T [] values;
         public of MyList () 
        { 
            values = new new T [size]; 
        } 
    } 
    
    void the Start () 
    { 
        of MyList < int > = myList_int new new of MyList < int > ();           // to T int 
        of MyList < String > = myList_string new new of MyList < String>(); // T 为 string
        myList_int.values[0] = 1;
        myList_string.values[0] = "Alice";
    }

• Generic function
  • Reduction function overloading, a generic T all the different types of adaptation parameters

  • // 交换a和b
    public void SwapValue<T>(ref T a, ref T b)
    {
        T temp = a;
        a = b;
        b = temp;
    }
    
    void Start()
    {
        int i1 = 1, i2 = 2;
        string s1 = "Alice", s2 = "Bob";
    
        SwapValue(ref i1, ref i2); // T 为 int
        SwapValue ( REF S1, REF S2); // T is a String 
        Debug.Log (I1); // Output: 2 
        Debug.Log (S1); // Output: Bob 
    }

• Generic delegate
  • Similar to the generic class definition

  • // 泛型委托
    delegate T NumberChanger<T>(T a, T b);
    
    public int AddNum(int a, int b)
    {
        return a + b;
    }
    public string AddString(string a, string b)
    {
        return a + b;
    }
    
    void Start()
    {
        // T 为 int
        NumberChanger<int> numberChanger_int = new NumberChanger<int>(AddNum);
        // T 为 string
        NumberChanger<string> numberChanger_string = new NumberChanger<string>(AddString);
    } 

 

• Multi-defined generic T
  • Generic necessarily only a T, can also define a plurality, T1, T2, T3 ...

  • // multiple T generic delegate 
    the delegate T3 NumberChanger <Tl, T2, T3> (Tl A, T2 B); 
    
    // int and float addition, return String 
    public  String AddNumToString ( int A, float B) 
    { 
        return (A + B) .ToString (); 
    } 
    
    void the Start () 
    { 
        // create a generic variable 
        NumberChanger < int , a float , String > = numberChanger new new NumberChanger < int , a float , String > (AddNumToString); 
    }

 

• Generic constraint ( WHERE )
  • T is of the generic type constraint, in addition to the definition of generic code behind   WHERE T: xxx  , xxx represents the type T must

• • For example:

  • public class Major // 职业
    {
    
    };
    public class Teacher : Major // 教师
    {
    
    }
    
    public class Person<T1, T2, T3> 
        where T1 : class    // T1 必须是个类 类型
        where T2 : struct   // T2 必须是个结构 类型
        where T3 : Major    // T3 必须是基类为Major的类 
    {
        T1 value1;
        T2 value2;
        T3 value3;
    }
    
    void Start()
    {
        // 报错：T1和T3不满足约束条件
        //Person<int, int, int> person1 = new Person<int, int, int>();
    
        // 正确：
        //  string  类型为 class System.String
        //  int     类型为 struct System.Int32
        //  Teacher 类型为 class Major
        Person<string, int, Teacher> person2 = new Person<string, int, Teacher>(); 
    }