Initial

config_pattern/Makefile

@@ -0,0 +1,2 @@
+run:
+	@go run main.go

config_pattern/go.mod

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+module patterns
+
+go 1.21.5

config_pattern/main.go

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+package main
+
+import "fmt"
+
+type SetFilterFunc func(options *FilterOptions)
+
+type FilterOptions struct {
+	Alive      *bool
+	Id         *int
+	ExternalId *string
+}
+
+type Filter struct {
+	Options FilterOptions
+}
+
+func (f *Filter) Dump() {
+	if f.Options.Alive != nil {
+		fmt.Printf("Alive: %v\n", *f.Options.Alive)
+	}
+	if f.Options.Id != nil {
+		fmt.Printf("Id: %v\n", *f.Options.Id)
+	}
+	if f.Options.ExternalId != nil {
+		fmt.Printf("ExternalId: %v\n", *f.Options.ExternalId)
+	}
+}
+
+func WithAlive(options *FilterOptions) {
+	alive := true
+	options.Alive = &alive
+}
+
+func WithId(id int) SetFilterFunc {
+	return func(options *FilterOptions) {
+		options.Id = &id
+	}
+}
+
+func WithExternalId(externalId string) SetFilterFunc {
+	return func(options *FilterOptions) {
+		options.ExternalId = &externalId
+	}
+}
+
+func NewFilter(opts ...SetFilterFunc) *Filter {
+	f := Filter{Options: FilterOptions{}}
+	for _, fn := range opts {
+		fn(&f.Options)
+	}
+	return &f
+}
+
+func main() {
+	var f *Filter
+
+	f = NewFilter()
+	f.Dump()
+
+	fmt.Println("-------------------")
+
+	f = NewFilter(WithId(123), WithAlive, WithExternalId("some-external-id"))
+	f.Dump()
+}