structure: add Fields() function, closes #4

README.md

@@ -28,7 +28,7 @@ s := &Server{
 
 #### ToMap()
 
-Convert to a `map[string]interface{}`
+Convert a struct to a `map[string]interface{}`
 
 ```go
 m := structure.ToMap(s)
@@ -39,8 +39,8 @@ fmt.Printf("%#v", m)
 
 #### ToSlice()
 
-Convert to a `[]interface{}`. Slice values are **sorted** by default according
-to the field names.
+Convert the values of a struct to a `[]interface{}`. Slice values are
+**sorted** by default according to the field names.
 
 ```go
 m := structure.ToSlice(s)
@@ -49,6 +49,18 @@ m := structure.ToSlice(s)
 fmt.Printf("%#v", m)
 ```
 
+#### Fields()
+
+Convert the fields of a struct to a `[]string`. Slice values are **sorted** by
+default according to the field names.
+
+```go
+m := structure.Fields(s)
+
+// prints: []string{"Enabled", "ID", "Name"}
+fmt.Printf("%#v", m)
+```
+
 #### IsStruct()
 
 Check if it's a struct or a pointer to struct

structure.go

@@ -74,7 +74,8 @@ func ToSlice(s interface{}) []interface{} {
 
 }
 
-// Fields returns a sorted slice of field names.
+// Fields returns a sorted slice of field names. Note that only exported
+// fields of a struct can be accessed, non exported fields  will be neglected.
 func Fields(s interface{}) []string {
 	m := ToMap(s)
 

structure_example_test.go

@@ -1,6 +1,9 @@
 package structure
 
-import "fmt"
+import (
+	"fmt"
+	"time"
+)
 
 func ExampleToMap() {
 	type Server struct {
@@ -73,3 +76,24 @@ func ExampleToSlice() {
 	// Output:
 	// []interface {}{false, 135790, "Fatih"}
 }
+
+func ExampleFields() {
+	type Access struct {
+		Name         string
+		LastAccessed time.Time
+		Number       int
+	}
+
+	s := &Access{
+		Name:         "Fatih",
+		LastAccessed: time.Now(),
+		Number:       1234567,
+	}
+
+	m := Fields(s)
+
+	// note that the output is sorted according to the field names
+	fmt.Printf("%#v\n", m)
+	// Output:
+	// []string{"LastAccessed", "Name", "Number"}
+}

structure_test.go

@@ -115,6 +115,10 @@ func TestToSlice(t *testing.T) {
 
 	s := ToSlice(T)
 
+	if typ := reflect.TypeOf(s).Kind(); typ != reflect.Slice {
+		t.Errorf("ToSlice should return a slice type, got: %v", typ)
+	}
+
 	inSlice := func(val interface{}) bool {
 		for _, v := range s {
 			if reflect.DeepEqual(v, val) {
@@ -130,3 +134,36 @@ func TestToSlice(t *testing.T) {
 		}
 	}
 }
+
+func TestFields(t *testing.T) {
+	var T = struct {
+		A string
+		B int
+		C bool
+	}{
+		A: "a-value",
+		B: 2,
+		C: true,
+	}
+
+	s := Fields(T)
+
+	if len(s) != 3 {
+		t.Errorf("Fields should return a slice of len 3, got: %d", len(s))
+	}
+
+	inSlice := func(val string) bool {
+		for _, v := range s {
+			if reflect.DeepEqual(v, val) {
+				return true
+			}
+		}
+		return false
+	}
+
+	for _, val := range []string{"A", "B", "C"} {
+		if !inSlice(val) {
+			t.Errorf("Fields should have the value %v", val)
+		}
+	}
+}