Don't panic in property accessors if type assertion fails

button.go

@@ -80,7 +80,7 @@ func (b *Button) init() {
 			return b.Text()
 		},
 		func(v interface{}) error {
-			return b.SetText(v.(string))
+			return b.SetText(assertStringOr(v, ""))
 		},
 		b.textChangedPublisher.Event()))
 }

checkbox.go

@@ -52,7 +52,7 @@ func NewCheckBox(parent Container) (*CheckBox, error) {
 			return cb.CheckState()
 		},
 		func(v interface{}) error {
-			cb.SetCheckState(v.(CheckState))
+			cb.SetCheckState(CheckState(assertIntOr(v, 0)))
 
 			return nil
 		},

combobox.go

@@ -142,7 +142,7 @@ func newComboBoxWithStyle(parent Container, style uint32) (*ComboBox, error) {
 			return cb.CurrentIndex()
 		},
 		func(v interface{}) error {
-			return cb.SetCurrentIndex(v.(int))
+			return cb.SetCurrentIndex(assertIntOr(v, -1))
 		},
 		cb.CurrentIndexChanged()))
 
@@ -151,7 +151,7 @@ func newComboBoxWithStyle(parent Container, style uint32) (*ComboBox, error) {
 			return cb.Text()
 		},
 		func(v interface{}) error {
-			return cb.SetText(v.(string))
+			return cb.SetText(assertStringOr(v, ""))
 		},
 		event))
 
@@ -183,7 +183,7 @@ func newComboBoxWithStyle(parent Container, style uint32) (*ComboBox, error) {
 		},
 		func(v interface{}) error {
 			if cb.Editable() {
-				return cb.SetText(v.(string))
+				return cb.SetText(assertStringOr(v, ""))
 			}
 
 			if cb.bindingValueProvider == nil {

dateedit.go

@@ -45,7 +45,7 @@ func newDateEdit(parent Container, style uint32) (*DateEdit, error) {
 			return de.Date()
 		},
 		func(v interface{}) error {
-			return de.SetDate(v.(time.Time))
+			return de.SetDate(assertTimeOr(v, time.Time{}))
 		},
 		de.dateChangedPublisher.Event()))
 

form.go

@@ -153,7 +153,7 @@ func (fb *FormBase) init(form Form) error {
 			return fb.Title()
 		},
 		func(v interface{}) error {
-			return fb.SetTitle(v.(string))
+			return fb.SetTitle(assertStringOr(v, ""))
 		},
 		fb.titleChangedPublisher.Event()))
 

groupbox.go

@@ -88,7 +88,7 @@ func NewGroupBox(parent Container) (*GroupBox, error) {
 			return gb.Title()
 		},
 		func(v interface{}) error {
-			return gb.SetTitle(v.(string))
+			return gb.SetTitle(assertStringOr(v, ""))
 		},
 		gb.titleChangedPublisher.Event()))
 

imageview.go

@@ -88,7 +88,7 @@ func NewImageView(parent Container) (*ImageView, error) {
 			return iv.Margin()
 		},
 		func(v interface{}) error {
-			return iv.SetMargin(v.(int))
+			return iv.SetMargin(assertIntOr(v, 0))
 		},
 		iv.MarginChanged()))
 

label.go

@@ -39,7 +39,7 @@ func NewLabelWithStyle(parent Container, style uint32) (*Label, error) {
 			return l.Text()
 		},
 		func(v interface{}) error {
-			return l.SetText(v.(string))
+			return l.setText(assertStringOr(v, ""))
 		},
 		l.textChangedPublisher.Event()))
 

lineedit.go

@@ -67,7 +67,7 @@ func newLineEdit(parent Window) (*LineEdit, error) {
 			return le.Text()
 		},
 		func(v interface{}) error {
-			return le.SetText(v.(string))
+			return le.SetText(assertStringOr(v, ""))
 		},
 		le.textChangedPublisher.Event()))
 

linklabel.go

@@ -38,7 +38,7 @@ func NewLinkLabel(parent Container) (*LinkLabel, error) {
 			return ll.Text()
 		},
 		func(v interface{}) error {
-			return ll.SetText(v.(string))
+			return ll.SetText(assertStringOr(v, ""))
 		},
 		ll.textChangedPublisher.Event()))
 

listbox.go

@@ -65,7 +65,7 @@ func NewListBoxWithStyle(parent Container, style uint32) (*ListBox, error) {
 			return lb.CurrentIndex()
 		},
 		func(v interface{}) error {
-			return lb.SetCurrentIndex(v.(int))
+			return lb.SetCurrentIndex(assertIntOr(v, -1))
 		},
 		lb.CurrentIndexChanged()))
 

numberedit.go

@@ -71,7 +71,7 @@ func NewNumberEdit(parent Container) (*NumberEdit, error) {
 			return ne.Prefix()
 		},
 		func(v interface{}) error {
-			return ne.SetPrefix(v.(string))
+			return ne.SetPrefix(assertStringOr(v, ""))
 		},
 		ne.prefixChangedPublisher.Event()))
 
@@ -89,7 +89,7 @@ func NewNumberEdit(parent Container) (*NumberEdit, error) {
 			return ne.Suffix()
 		},
 		func(v interface{}) error {
-			return ne.SetSuffix(v.(string))
+			return ne.SetSuffix(assertStringOr(v, ""))
 		},
 		ne.suffixChangedPublisher.Event()))
 
@@ -98,7 +98,7 @@ func NewNumberEdit(parent Container) (*NumberEdit, error) {
 			return ne.Value()
 		},
 		func(v interface{}) error {
-			return ne.SetValue(v.(float64))
+			return ne.SetValue(assertFloat64Or(v, 0.0))
 		},
 		ne.edit.valueChangedPublisher.Event()))
 

slider.go

@@ -54,7 +54,7 @@ func NewSliderWithOrientation(parent Container, orientation Orientation) (*Slide
 			return sl.Value()
 		},
 		func(v interface{}) error {
-			sl.SetValue(v.(int))
+			sl.SetValue(assertIntOr(v, 0))
 			return nil
 		},
 		sl.valueChangedPublisher.Event()))

tableview.go

@@ -259,7 +259,7 @@ func NewTableViewWithCfg(parent Container, cfg *TableViewCfg) (*TableView, error
 			return tv.CurrentIndex()
 		},
 		func(v interface{}) error {
-			return tv.SetCurrentIndex(v.(int))
+			return tv.SetCurrentIndex(assertIntOr(v, -1))
 		},
 		tv.CurrentIndexChanged()))
 

tabpage.go

@@ -7,8 +7,9 @@
 package walk
 
 import (
-	"github.com/lxn/win"
 	"strconv"
+
+	"github.com/lxn/win"
 )
 
 const tabPageWindowClass = `\o/ Walk_TabPage_Class \o/`
@@ -49,7 +50,7 @@ func NewTabPage() (*TabPage, error) {
 			return tp.Title()
 		},
 		func(v interface{}) error {
-			return tp.SetTitle(v.(string))
+			return tp.SetTitle(assertStringOr(v, ""))
 		},
 		tp.titleChangedPublisher.Event()))
 

tabwidget.go

@@ -79,7 +79,7 @@ func NewTabWidget(parent Container) (*TabWidget, error) {
 			return tw.CurrentIndex()
 		},
 		func(v interface{}) error {
-			return tw.SetCurrentIndex(v.(int))
+			return tw.SetCurrentIndex(assertIntOr(v, -1))
 		},
 		tw.CurrentIndexChanged()))
 

textedit.go

@@ -55,7 +55,7 @@ func NewTextEditWithStyle(parent Container, style uint32) (*TextEdit, error) {
 			return te.Text()
 		},
 		func(v interface{}) error {
-			return te.SetText(v.(string))
+			return te.SetText(assertStringOr(v, ""))
 		},
 		te.textChangedPublisher.Event()))
 

util.go

@@ -109,6 +109,38 @@ func uint16RemoveUint16(s []uint16, v uint16) []uint16 {
 	return ret
 }
 
+func assertFloat64Or(value interface{}, defaultValue float64) float64 {
+	if f, ok := value.(float64); ok {
+		return f
+	}
+
+	return defaultValue
+}
+
+func assertIntOr(value interface{}, defaultValue int) int {
+	if n, ok := value.(int); ok {
+		return n
+	}
+
+	return defaultValue
+}
+
+func assertStringOr(value interface{}, defaultValue string) string {
+	if s, ok := value.(string); ok {
+		return s
+	}
+
+	return defaultValue
+}
+
+func assertTimeOr(value interface{}, defaultValue time.Time) time.Time {
+	if t, ok := value.(time.Time); ok {
+		return t
+	}
+
+	return defaultValue
+}
+
 func ParseFloat(s string) (float64, error) {
 	s = strings.TrimSpace(s)
 

webview.go

@@ -177,7 +177,7 @@ func NewWebView(parent Container) (*WebView, error) {
 			return url
 		},
 		func(v interface{}) error {
-			return wv.SetURL(v.(string))
+			return wv.SetURL(assertStringOr(v, ""))
 		},
 		wv.urlChangedPublisher.Event()))
 

widget.go

@@ -129,7 +129,7 @@ func (wb *WidgetBase) init(widget Widget) error {
 			return wb.window.(Widget).ToolTipText()
 		},
 		func(v interface{}) error {
-			wb.window.(Widget).SetToolTipText(v.(string))
+			wb.window.(Widget).SetToolTipText(assertStringOr(v, ""))
 			return nil
 		},
 		wb.toolTipTextChangedPublisher.Event())