update-components (#986)

- implement update function
- create an example demo

demo/blocks_update/run.py

@@ -0,0 +1,17 @@
+from gradio import Dropdown, Blocks, Slider
+
+
+def update_dropdown_choices(val):
+    if val < 50:
+        opts = ["fail", "repeat"]
+    else:
+        opts = ["succeed", "repeat"]
+    return Dropdown.update(choices=opts)
+
+
+with Blocks() as block:
+    s = Slider(default_value=0, minimum=0, maximum=100)
+    d = Dropdown(choices=["fake", "choices", "exist"])
+
+    s.change(fn=update_dropdown_choices, inputs=[s], outputs=[d])
+    block.launch()

gradio/components.py

@@ -209,6 +209,17 @@ class Component(Block):
         """
         return x
 
+    @staticmethod
+    def update(**kwargs) -> dict:
+        """
+        Updates component parameters
+
+        @param kwargs: Updating component parameters
+        @return: Updated component parameters
+        """
+        kwargs["__type__"] = "update"
+        return kwargs
+
 
 class Textbox(Component):
     """