Add function to convert []interface -> []string (#69)

* Add function to convert []interface -> []string

sliceutil/sliceutil.go

@@ -8,6 +8,7 @@ package sliceutil // import "github.com/teamwork/utils/sliceutil"
 
 import (
 	"math/rand"
+	"reflect"
 	"sort"
 	"strconv"
 	"strings"
@@ -214,3 +215,24 @@ func StringMap(list []string, f func(string) string) []string {
 
 	return ret
 }
+
+// InterfaceSliceTo converts []interface to any given slice.
+// It will ~optimistically~ try to convert interface item to the dst item type
+func InterfaceSliceTo(src []interface{}, dst interface{}) interface{} {
+	dstt := reflect.TypeOf(dst)
+	if dstt.Kind() != reflect.Slice {
+		panic("`dst` is not an slice")
+	}
+
+	dstV := reflect.ValueOf(dst)
+
+	for i := range src {
+		if i < dstV.Len() {
+			dstV.Index(i).Set(reflect.ValueOf(src[i]).Convert(dstt.Elem()))
+			continue
+		}
+		dstV = reflect.Append(dstV, reflect.ValueOf(src[i]).Convert(dstt.Elem()))
+	}
+
+	return dstV.Interface()
+}

sliceutil/sliceutil_test.go

@@ -528,3 +528,49 @@ func TestStringMap(t *testing.T) {
 		})
 	}
 }
+
+func TestInterfaceSliceTo(t *testing.T) {
+	{
+		src := []interface{}{"1", "2", "3", "4", "5"}
+		want := []string{"1", "2", "3", "4", "5"}
+		input := []string{""}
+
+		result := InterfaceSliceTo(src, input)
+		if !reflect.DeepEqual(result, want) {
+			t.Fatalf("want %+v(%T),\tgot %+v(%T)", want, want, result, result)
+		}
+	}
+
+	{
+		src := []interface{}{"1", "2", "3", "4", "5"}
+		want := []string{"1", "2", "3", "4", "5"}
+		input := []string{}
+
+		result := InterfaceSliceTo(src, input)
+		if !reflect.DeepEqual(result, want) {
+			t.Fatalf("want %+v(%T),\tgot %+v(%T)", want, want, result, result)
+		}
+	}
+
+	{
+		src := []interface{}{1, 2, 3, 4, 5}
+		want := []int{1, 2, 3, 4, 5}
+		input := []int{0, 0}
+
+		result := InterfaceSliceTo(src, input)
+		if !reflect.DeepEqual(result, want) {
+			t.Fatalf("want %+v(%T),\tgot %+v(%T)", want, want, result, result)
+		}
+	}
+
+	{
+		src := []interface{}{1, 2, 3, 4, 5}
+		want := []int64{1, 2, 3, 4, 5}
+		input := []int64{0, 0}
+
+		result := InterfaceSliceTo(src, input)
+		if !reflect.DeepEqual(result, want) {
+			t.Fatalf("want %+v(%T),\tgot %+v(%T)", want, want, result, result)
+		}
+	}
+}