当所需产品较为复杂且需要多个步骤才能完成时， 也可以使用生成器模式。 在这种情况下， 使用多个构造方法比仅仅使用一个复杂可怕的构造函数更简单。 分为多个步骤进行构建的潜在问题是， 构建不完整的和不稳定的产品可能会被暴露给客户端。 生成器模式能够在产品完成构建之前使其处于私密状态。
在下方的代码中， 我们可以看到 iglooBuilder冰屋生成器与 normalBuilder普通房屋生成器可建造不同类型房屋， 即 igloo冰屋和 normalHouse普通房屋。 每种房屋类型的建造步骤都是相同的。 主管 （可选） 结构体可对建造过程进行组织。
iBuilder.go: 生成器接口
package main type iBuilder interface { setWindowType() setDoorType() setNumFloor() getHouse() house } func getBuilder(builderType string) iBuilder { if builderType == "normal" { return &normalBuilder{} } if builderType == "igloo" { return &iglooBuilder{} } return nil } normalBuilder.go: 具体生成器 package main type normalBuilder struct { windowType string doorType string floor int } func newNormalBuilder() *normalBuilder { return &normalBuilder{} } func (b *normalBuilder) setWindowType() { b.windowType = "Wooden Window" } func (b *normalBuilder) setDoorType() { b.doorType = "Wooden Door" } func (b *normalBuilder) setNumFloor() { b.floor = 2 } func (b *normalBuilder) getHouse() house { return house{ doorType: b.doorType, windowType: b.windowType, floor: b.floor, } }
iglooBuilder.go: 具体生成器
package main type iglooBuilder struct { windowType string doorType string floor int } func newIglooBuilder() *iglooBuilder { return &iglooBuilder{} } func (b *iglooBuilder) setWindowType() { b.windowType = "Snow Window" } func (b *iglooBuilder) setDoorType() { b.doorType = "Snow Door" } func (b *iglooBuilder) setNumFloor() { b.floor = 1 } func (b *iglooBuilder) getHouse() house { return house{ doorType: b.doorType, windowType: b.windowType, floor: b.floor, } }
house.go: 产品
package main type house struct { windowType string doorType string floor int } director.go: 主管 package main type director struct { builder iBuilder } func newDirector(b iBuilder) *director { return &director{ builder: b, } } func (d *director) setBuilder(b iBuilder) { d.builder = b } func (d *director) buildHouse() house { d.builder.setDoorType() d.builder.setWindowType() d.builder.setNumFloor() return d.builder.getHouse() }
main.go: 客户端代码
package main import "fmt" func main() { normalBuilder := getBuilder("normal") iglooBuilder := getBuilder("igloo") director := newDirector(normalBuilder) normalHouse := director.buildHouse() fmt.Printf("Normal House Door Type: %s\n", normalHouse.doorType) fmt.Printf("Normal House Window Type: %s\n", normalHouse.windowType) fmt.Printf("Normal House Num Floor: %d\n", normalHouse.floor) director.setBuilder(iglooBuilder) iglooHouse := director.buildHouse() fmt.Printf("\nIgloo House Door Type: %s\n", iglooHouse.doorType) fmt.Printf("Igloo House Window Type: %s\n", iglooHouse.windowType) fmt.Printf("Igloo House Num Floor: %d\n", iglooHouse.floor) }
output.txt: 执行结果
Normal House Door Type: Wooden Door Normal House Window Type: Wooden Window Normal House Num Floor: 2 Igloo House Door Type: Snow Door Igloo House Window Type: Snow Window Igloo House Num Floor: 1
