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62 lines
1.1 KiB
Markdown
62 lines
1.1 KiB
Markdown
# Builder Pattern
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Builder pattern separates the construction of a complex object from its
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representation so that the same construction process can create different
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representations.
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In Go, normally a configuration struct is used to achieve the same behavior,
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however passing a struct to the builder method fills the code with boilerplate
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`if cfg.Field != nil {...}` checks.
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## Implementation
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```go
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package car
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type Speed float64
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const (
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MPH Speed = 1
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KPH = 1.60934
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)
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type Color string
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const (
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BlueColor Color = "blue"
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GreenColor = "green"
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RedColor = "red"
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)
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type Wheels string
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const (
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SportsWheels Wheels = "sports"
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SteelWheels = "steel"
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)
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type Builder interface {
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Color(Color) Builder
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Wheels(Wheels) Builder
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TopSpeed(Speed) Builder
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Build() Interface
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}
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type Interface interface {
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Drive() error
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Stop() error
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}
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```
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## Usage
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```go
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assembly := car.NewBuilder().Paint(car.RedColor)
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familyCar := assembly.Wheels(car.SportsWheels).TopSpeed(50 * car.MPH).Build()
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familyCar.Drive()
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sportsCar := assembly.Wheels(car.SteelWheels).TopSpeed(150 * car.MPH).Build()
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sportsCar.Drive()
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```
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