# Simple factory and single case design mode

Source: Internet
Author: User

One: Design mode

Concept:

Propose specific solutions for specific issues

II: Simple Factory

eg

Using polymorphic and simple factory design patterns to achieve the calculator, the effect:

`    //Parent Class     Public Abstract classOperation { Public DoubleNumbera {Get;Set; }  Public DoubleNumberb {Get;Set; }  Public Abstract DoubleGetResult ();} //sub-class addition     Public classoperationadd:operation { Public Override DoubleGetResult () {Doubleresult = Numbera +Numberb; returnresult; }}      //sub-class subtraction  Public classoperationjian:operation { Public Override DoubleGetResult () {Doubleresult = Numbera-Numberb; returnresult; }    }   //sub-class multiplication   Public classoperationcheng:operation { Public Override DoubleGetResult () {Doubleresult = Numbera *Numberb; returnresult; }    }     //sub-class division     Public  classoperationchu:operation { Public Override DoubleGetResult () {if(Numberb = =0)           {               Throw NewException ("the divisor cannot be 0! "); }           Doubleresult = Numbera/Numberb; returnresult; }    }`

Get two operands in the Calculate button, as well as operators, methods of calculation

`            //get two operand (x )            intNUM1 =Convert.ToInt32 (Txtlist1.text); intnum2 =Convert.ToInt32 (Txtlist2.text); //Get operator            stringOper =Cbolist.text; Operation Calc=operationfactory.createinstance (OPER); Calc. Numbera=NUM1; Calc. Numberb=num2; //calculation Method            intresult =0; Try{result=Convert.ToInt32 (Calc.            GetResult ()); }            Catch(Exception ex) {MessageBox.Show (ex).                Message); Throw; } Label1. Text= result. ToString ();`

Factory class: (CORE)

Three: Single case mode

Singleton mode requires that a class can have only one object

Four steps:

①: Defines a static variable with the same type as the current class name

②: Change construction to private

③: Defines a static method that assigns a value to a static variable, instantiates the object, and returns an instance reference

④: Empty the static variable

`         Public Partial classForm1:form {//defines a static variable with the same type as the current class name         Public StaticForm1 frm; //change construction to private       PrivateForm1 () {InitializeComponent (); }        //define a static method to assign a value to a static variable        Public StaticForm1 getinstance () {if(frm = =NULL) {frm=NewForm1 (); }           returnfrm; }        //empty a static variable        Private voidForm1_formclosing (Objectsender, FormClosingEventArgs e) {frm=NULL; }`

Simple factory and single case design mode

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