onLoaded

Signed-off-by: Paweł Gronowski <[email protected]>

livefile.go

@@ -22,6 +22,7 @@ type LiveFile[StateT any] struct {
 
 	defaultFunc func() StateT
 	errHandler  func(context.Context, error)
+	onLoaded    func(context.Context, *StateT)
 }
 
 // The default error handler used for all LiveFile instances created without an
@@ -117,6 +118,10 @@ func (lf *LiveFile[T]) forceLoad(ctx context.Context, file *os.File) {
 	}
 	if err != nil {
 		lf.errHandler(ctx, fmt.Errorf("invalid JSON: %w", err))
+	} else {
+		if lf.onLoaded != nil {
+			lf.onLoaded(ctx, &lf.cached)
+		}
 	}
 }
 

opts.go

@@ -20,3 +20,14 @@ func WithErrorHandler[T any](f func(context.Context, error)) Opt[T] {
 		s.errHandler = f
 	}
 }
+
+// WithLoadedCallback sets the function that will be called when the file is
+// reloaded from the filesystem.
+// The function will be called with the context and a pointer to the new data.
+// Any access to the data MUST happen inside the callback and MUST NOT be
+// stored outside of it.
+func WithLoadedCallback[T any](f func(context.Context, *T)) Opt[T] {
+	return func(s *LiveFile[T]) {
+		s.onLoaded = f
+	}
+}