Add ToDurationSlice()

cast.go

@@ -151,3 +151,9 @@ func ToIntSlice(i interface{}) []int {
 	v, _ := ToIntSliceE(i)
 	return v
 }
+
+// ToDurationSlice casts an interface to a []time.Duration type.
+func ToDurationSlice(i interface{}) []time.Duration {
+	v, _ := ToDurationSliceE(i)
+	return v
+}

cast_test.go

@@ -975,6 +975,38 @@ func TestToStringSliceE(t *testing.T) {
 	}
 }
 
+func TestToDurationSliceE(t *testing.T) {
+	tests := []struct {
+		input  interface{}
+		expect []time.Duration
+		iserr  bool
+	}{
+		{[]string{"1s", "1m"}, []time.Duration{time.Second, time.Minute}, false},
+		{[]int{1, 2}, []time.Duration{1, 2}, false},
+		{[]interface{}{1, 3}, []time.Duration{1, 3}, false},
+		// errors
+		{nil, nil, true},
+		{testing.T{}, nil, true},
+	}
+
+	for i, test := range tests {
+		errmsg := fmt.Sprintf("i = %d", i) // assert helper message
+
+		v, err := ToDurationSliceE(test.input)
+		if test.iserr {
+			assert.Error(t, err, errmsg)
+			continue
+		}
+
+		assert.NoError(t, err, errmsg)
+		assert.Equal(t, test.expect, v, errmsg)
+
+		// Non-E test
+		v = ToDurationSlice(test.input)
+		assert.Equal(t, test.expect, v, errmsg)
+	}
+}
+
 func TestToBoolE(t *testing.T) {
 	tests := []struct {
 		input  interface{}

caste.go

@@ -1077,6 +1077,35 @@ func ToIntSliceE(i interface{}) ([]int, error) {
 	}
 }
 
+// ToDurationSliceE casts an interface to a []time.Duration type.
+func ToDurationSliceE(i interface{}) ([]time.Duration, error) {
+	if i == nil {
+		return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+	}
+
+	switch v := i.(type) {
+	case []time.Duration:
+		return v, nil
+	}
+
+	kind := reflect.TypeOf(i).Kind()
+	switch kind {
+	case reflect.Slice, reflect.Array:
+		s := reflect.ValueOf(i)
+		a := make([]time.Duration, s.Len())
+		for j := 0; j < s.Len(); j++ {
+			val, err := ToDurationE(s.Index(j).Interface())
+			if err != nil {
+				return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+			}
+			a[j] = val
+		}
+		return a, nil
+	default:
+		return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+	}
+}
+
 // StringToDate attempts to parse a string into a time.Time type using a
 // predefined list of formats.  If no suitable format is found, an error is
 // returned.