builder_pattern.go

package main

import (
	"fmt"
)

type SQLBuilder interface {
	Select() SQLBuilder
	Star() SQLBuilder
	From(table string) SQLBuilder
	Where(condition string) SQLBuilder
	Build() string
}

type builder struct {
	s string
}

func (b *builder) Select() SQLBuilder {
	b.s = b.s + "SELECT "
	return b
}

func (b *builder) Star() SQLBuilder {
	b.s = b.s + " * "
	return b
}

func (b *builder) From(table string) SQLBuilder {
	b.s = b.s + " FROM " + table + " "
	return b
}

func (b *builder) Where(condition string) SQLBuilder {
	b.s = b.s + " WHERE " + condition + " "
	return b
}

func (b *builder) Build() string {
	return b.s
}

func main() {
	b := &builder{}
	s := b.Select().Star().From("foo")
	fmt.Println(s)
}