functional options pattern

functional_options.go

package main

import "fmt"

type Student struct {
    Name string
    Age int
    Address *string // optional
    PhoneNumber *int // optional
}

type OptionalStudentValues func(*Student)

func NewStudent(name string, age, int, opts ...OptionalStudentValues) *Student {
    stu := &Student{
        Name: name,
        Age: age,
    }
    if len(opts) > 0 {
        for _, opt := range opts {
            opt(stu)
        }
    }
    
    return stu
}

func WithAddress(addr string) OptionalStudentValues {
    return func(s *Student) {
        s.Address = &addr
    }
}

func WithPhoneNumber(num int) OptionalStudentValues {
    return func(s *Student) {
        s.PhoneNumber = &int
    }
}

func main() {
    stuAddr := "Addr"
    stuPhone := 13966272617
    stu := NewStudent("Ader", 99, WithAddress(stuAddr), WithPhoneNumber(stuPhone))
    fmt.Println(stu)
}