boolProperty: Accept source of type Expression

2 files changed, 23 insertions, 1 deletions

diff --git a/declarative/builder.go b/declarative/builder.go
index b01a110c..e376fd9d 100644
--- a/declarative/builder.go
+++ b/declarative/builder.go
@@ -683,6 +683,10 @@ func (se subExpressions) Get(name string) (interface{}, error) {
 	return nil, fmt.Errorf(`invalid sub expression: "%s"`, name)
 }
 
+func (e *expression) String() string {
+	return e.text
+}
+
 func (e *expression) Value() interface{} {
 	val, err := e.expr.Eval(e.subExprsByPath)
 	if err != nil {
diff --git a/property.go b/property.go
index 0230860f..55fc5043 100644
--- a/property.go
+++ b/property.go
@@ -8,6 +8,7 @@ package walk
 
 import (
 	"errors"
+	"fmt"
 )
 
 var (
@@ -251,8 +252,25 @@ func (bp *boolProperty) SetSource(source interface{}) error {
 				bp.Set(source.Satisfied())
 			})
 
+		case Expression:
+			if err := checkPropertySource(bp, source); err != nil {
+				return err
+			}
+
+			if satisfied, ok := source.Value().(bool); ok {
+				if err := bp.Set(satisfied); err != nil {
+					return err
+				}
+			}
+
+			bp.sourceChangedHandle = source.Changed().Attach(func() {
+				if satisfied, ok := source.Value().(bool); ok {
+					bp.Set(satisfied)
+				}
+			})
+
 		default:
-			return newError("invalid source type")
+			return newError(fmt.Sprintf(`invalid source: "%s" of type %T`, source, source))
 		}
 	}