Original design mode (Golang) Five, factory method mode

This is a creation in Article, where the information may have evolved or changed.

Pattern feature: Defines an interface for creating objects, letting subclasses decide which class to instantiate. This causes the instantiation of a class to be deferred to its subclasses.
Program Example: Calculator.

Package Mainimport ("FMT") type operation struct {a float64b float64}type Operationi interface {getresult () Float64seta (fl Oat64) Setb (float64)}func (op *operation) SetA (a float64) {Op.a = A}func (op *operation) Setb (b float64) {op.b = B}type Add  Operation struct {operation}func (this *addoperation) GetResult () float64 {return this.a + this.b}type suboperation struct  {Operation}func (this *suboperation) GetResult () float64 {return this.a-this.b}type muloperation struct {operation}func (This *muloperation) GetResult () float64 {return THIS.A * this.b}type divoperation struct {operation}func (this *divoperation) GetResult () Floa T64 {return This.a/this.b}type ifactory interface {createoperation () Operation}type addfactory struct {}func (this *ADDF actory) createoperation () Operationi {return & (addoperation{})}type subfactory struct {}func (this *subfactory) CreateOperation () Operationi {return & (suboperation{})}type mulfactory struct {}func (this *mulfactory) CreateOperation () OperaTioni {return & (muloperation{})}type divfactory struct {}func (this *divfactory) createoperation () Operationi { Return & (divoperation{})}func Main () {FAC: = & (addfactory{}) Oper: = FAC. CreateOperation () Oper. SetA (1) Oper. SETB (2) fmt. Println (Oper. GetResult ())}