Merge pull request #3027 from andydotxyz/chrisbirster-new-string-with…

…-format

Completing Chrisbirster new string with format

data/binding/sprintf.go

@@ -20,7 +20,7 @@ type sprintfString struct {
 // and will have all the same limitation as those function.
 //
 // Since: 2.2
-func NewSprintf(format string, b ...DataItem) (String, error) {
+func NewSprintf(format string, b ...DataItem) String {
 	ret := &sprintfString{
 		String: NewString(),
 		format: format,
@@ -31,7 +31,7 @@ func NewSprintf(format string, b ...DataItem) (String, error) {
 		value.AddListener(ret)
 	}
 
-	return ret, nil
+	return ret
 }
 
 func (s *sprintfString) DataChanged() {
@@ -203,3 +203,16 @@ func (s *sprintfString) Set(str string) error {
 
 	return nil
 }
+
+// StringToStringWithFormat creates a binding that converts a string to another string using the specified format.
+// Changes to the returned String will be pushed to the passed in String and setting a new string value will parse and
+// set the underlying String if it matches the format and the parse was successful.
+//
+// Since: 2.2
+func StringToStringWithFormat(str String, format string) String {
+	if format == "%s" { // Same as not using custom formatting.
+		return str
+	}
+
+	return NewSprintf(format, str)
+}

data/binding/sprintf_test.go

@@ -25,10 +25,8 @@ func TestSprintfConversionRead(t *testing.T) {
 	bu := BindURI(&u)
 
 	format := "Bool %v, Float %f, Int %i, Rune %v, String '%s', URI '%s'"
-	sp, err := NewSprintf(format, bb, bf, bi, br, bs, bu)
+	sp := NewSprintf(format, bb, bf, bi, br, bs, bu)
 	expected := fmt.Sprintf(format, b, f, i, r, s, u)
-
-	assert.Nil(t, err)
 	assert.NotNil(t, sp)
 
 	waitForItems()
@@ -73,10 +71,8 @@ func TestSprintfConversionReadWrite(t *testing.T) {
 	bu := BindURI(&u)
 
 	format := "Bool %v , Float %f , Int %v , Rune %v , String %s , URI %s"
-	sp, err := NewSprintf(format, bb, bf, bi, br, bs, bu)
+	sp := NewSprintf(format, bb, bf, bi, br, bs, bu)
 	expected := fmt.Sprintf(format, b, f, i, r, s, u)
-
-	assert.Nil(t, err)
 	assert.NotNil(t, sp)
 
 	waitForItems()
@@ -109,3 +105,37 @@ func TestSprintfConversionReadWrite(t *testing.T) {
 	assert.Equal(t, expectedChange, sChange)
 	assert.NotEqual(t, sGenerated, sChange)
 }
+
+func TestNewStringWithFormat(t *testing.T) {
+	var s = "this is a string"
+	bs := BindString(&s)
+
+	format := "String %s"
+	sp := StringToStringWithFormat(bs, format)
+	expected := fmt.Sprintf(format, s)
+	assert.NotNil(t, sp)
+
+	waitForItems()
+
+	sGenerated, err := sp.Get()
+	assert.Nil(t, err)
+	assert.NotNil(t, sGenerated)
+	assert.Equal(t, expected, sGenerated)
+
+	err = sp.Set("String nospacestring")
+	assert.Nil(t, err)
+
+	waitForItems()
+
+	assert.Equal(t, s, "nospacestring")
+	expectedChange := fmt.Sprintf(format, s)
+	sChange, err := sp.Get()
+	assert.Nil(t, err)
+	assert.NotNil(t, sChange)
+	assert.Equal(t, expectedChange, sChange)
+	assert.NotEqual(t, sGenerated, sChange)
+
+	emptyFormat := "%s"
+	wrapped := StringToStringWithFormat(bs, emptyFormat)
+	assert.Equal(t, bs, wrapped)
+}