Add `ToUUID` casting

This close #92

cast.go

@@ -6,7 +6,11 @@
 // Package cast provides easy and safe casting in Go.
 package cast
 
-import "time"
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
 
 // ToBool casts an interface to a bool type.
 func ToBool(i interface{}) bool {
@@ -169,3 +173,9 @@ func ToDurationSlice(i interface{}) []time.Duration {
 	v, _ := ToDurationSliceE(i)
 	return v
 }
+
+// ToUUID casts an interface to a uint type.
+func ToUUID(i interface{}) uuid.UUID {
+	v, _ := ToUUIDE(i)
+	return v
+}

caste.go

@@ -14,6 +14,8 @@ import (
 	"strconv"
 	"strings"
 	"time"
+
+	"github.com/google/uuid"
 )
 
 var errNegativeNotAllowed = errors.New("unable to cast negative value")
@@ -756,6 +758,24 @@ func ToUint8E(i interface{}) (uint8, error) {
 	}
 }
 
+// ToUUIDE casts an interface to a uint type.
+func ToUUIDE(i interface{}) (uuid.UUID, error) {
+	i = indirect(i)
+	var b uuid.UUID
+
+	switch s := i.(type) {
+	case string:
+		return uuid.Parse(s)
+	case interface{}:
+		if str, err := ToStringE(s); err == nil {
+			return uuid.Parse(str)
+		}
+		return b, fmt.Errorf("unable to cast %#v of type %T to UUID", i, i)
+	default:
+		return b, fmt.Errorf("unable to cast %#v of type %T to UUID", i, i)
+	}
+}
+
 // From html/template/content.go
 // Copyright 2011 The Go Authors. All rights reserved.
 // indirect returns the value, after dereferencing as many times

go.mod

@@ -2,6 +2,9 @@ module github.com/spf13/cast
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/google/uuid v1.1.1
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/stretchr/testify v1.2.2
 )
+
+go 1.13

go.sum

@@ -1,5 +1,7 @@
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
+github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 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/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=