Initial ADT example

.gitignore

@@ -0,0 +1 @@
+.idea

adt/adt.go

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+package adt
+
+import "adtExample/lib"
+
+type ofUnion interface {
+	lib.TypeA | lib.TypeB
+}
+
+type union interface {
+	atd()
+}
+
+type TypeAContainer struct {
+	v lib.TypeA
+}
+
+func (t TypeAContainer) atd() {}
+
+type TypeBContainer struct {
+	v lib.TypeB
+}
+
+func (t TypeBContainer) atd() {}
+
+type Atd struct {
+	v union
+}
+
+type doFnTypeAFn func(aType lib.TypeA)
+type doFnTypeBFn func(aType lib.TypeB)
+
+type doFns struct {
+	doFnTypeA doFnTypeAFn
+	doFnTypeB doFnTypeBFn
+}
+
+type doChainA struct {
+	doBuilder doFns
+}
+
+type doChainB struct {
+	fns doFns
+}
+
+type doChainExecutor struct {
+	fns doFns
+}
+
+func (chain *doChainB) WithTypeB(fn doFnTypeBFn) *doChainExecutor {
+	chain.fns.doFnTypeB = fn
+	return &doChainExecutor{chain.fns}
+}
+
+func (chain *doChainA) WithTypeA(fn doFnTypeAFn) *doChainB {
+	chain.doBuilder.doFnTypeA = fn
+	return &doChainB{chain.doBuilder}
+}
+
+func Do() *doChainA {
+	return &doChainA{doFns{}}
+}
+
+func (e doChainExecutor) Exec(of *Atd) {
+	switch container := of.v.(type) {
+	case TypeAContainer:
+		e.fns.doFnTypeA(container.v)
+	case TypeBContainer:
+		e.fns.doFnTypeB(container.v)
+	}
+}
+
+func Of[T ofUnion](union T) *Atd {
+	var t interface{}
+	t = union
+	switch v := t.(type) {
+	case lib.TypeA:
+		return &Atd{TypeAContainer{v}}
+	case lib.TypeB:
+		return &Atd{TypeBContainer{v}}
+	default:
+		panic("called Of with disallowed type")
+	}
+}

adt/adt_test.go

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+package adt_test
+
+import (
+	"adtExample/adt"
+	"adtExample/lib"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestExecutingWithTwoTypes(t *testing.T) {
+	typeACalled := false
+	typeBCalled := false
+
+	do := adt.Do().
+		WithTypeA(func(typeA lib.TypeA) { typeACalled = true }).
+		WithTypeB(func(typeB lib.TypeB) { typeBCalled = true })
+
+	do.Exec(adt.Of(lib.TypeA{}))
+
+	require.Equal(t, typeACalled, true)
+	require.Equal(t, typeBCalled, false)
+
+	typeACalled = false
+	typeBCalled = false
+
+	do.Exec(adt.Of(lib.TypeB{}))
+
+	require.Equal(t, typeACalled, false)
+	require.Equal(t, typeBCalled, true)
+}

go.mod

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+module adtExample
+
+go 1.18
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.1.0 // indirect
+	github.com/stretchr/testify v1.7.1 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)

go.sum

@@ -0,0 +1,11 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

lib/types.go

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+package lib
+
+type TypeA struct {
+}
+
+type TypeB struct {
+}