Design Patterns: Singleton and Simple Factory

Singleton design pattern: Instantiate only one Class object!

1  Public class Person2     {3        //1: First define a static variable4        //2: Privatize the constructor of this class5        //3: Define a static method that assigns the class object to this static variable6        //4: Use class in other classes. Method name to invoke the object7         Public StaticPerson p1;8        PrivatePerson ()9        {Ten        } One         Public StaticPerson Get () A        { -            if(P1 = =NULL) -            { theP1 =NewPerson (); -            } -            returnP1; -        } +     } - class Program +     { A         Static voidMain (string[] args) at         { -person P1 =person.get (); -         } -}

Design Pattern II: Simple Factory

Defines a factory class that can return instances of different classes depending on the parameters, and the instances that are created usually have a common parent class.

1: Define a parent class

 Public Abstract class person    {       publicabstractvoid  Say ();         Public Person ()       {       }    }

2: Definition of two sub-classes

1     classFather:person2     {3          Public Override voidSay ()4         {5Console.WriteLine ("I'm a dad .");6         }7     }8  classSon:person9     {Ten          Public Override voidSay () One         { AConsole.WriteLine ("I'm a son ."); -         } -}

3: Define Simple factory class

1   Public Abstract classTool2     {3         Public StaticPerson St (stringtype)4        {5Person p1=NULL;6            Switch(type)7            {8                 Case"dad":9p1=NewFather ();Ten                     Break; One                 Case "son": AP1 =NewSon (); -                     Break; -  the  -  -            } -            returnP1; +  -        } +}

Design Patterns: Singleton and Simple Factory