# Upgrading to v0.12

Between v0.11 and v0.12 some breaking changes have occurred, so here comes the guide that will help you adjust your code to the new API. See the [release notes](https://github.com/membraneframework/membrane_core/releases/tag/v0.12.1) for details.

## Deps upgrade

Upgrade `membrane_core` to `v0.12.1`.

```elixir 
defp deps do
   [
     {:membrane_core, "~> 0.12.1"},
     ...
   ]
end
```

## Implement `handle_child_pad_removed/4` callback in bins and pipelines, if it is needed

Now, if bin removes its pad (e.g. by removing an element linked to the bin's inner pad), bin's parent has to have implemented proper `handle_child_pad_removed/4` callback, to handle it. If there is no such a callback, default behaviour is to raise an error. 

```elixir
@impl true
def handle_child_pad_removed(:rtp, Pad.ref(:rtp_input, _ssrc), _ctx, state) do
  # ...
end
```

## Remove `:playback` action

Now, membrane pipelines enter the playing playback by default and they don't have to return a `:playback` action to do it. 

```diff
- @impl true 
- def handle_setup(_ctx, state) do
- {[playback: :playing], state}
- end
```
Instead of it, there is a new action introduced in `membrane_core` v0.12, `setup: :incomplete | :complete`. If you want to defer a moment when a component enters the playing playback, you can return `{:setup, :incomplete}` action from `handle_setup` callback. If you do that, a component will enter the playing playback only when you return `{:setup, :complete}` action from another callback, e.g. `handle_info`.

```diff 
- @impl true 
- def handle_setup(_ctx, state) do
-   Process.send_after(self(), :play, 1000)
-   {[], state}
- end
-
- @impl true 
- def handle_info(:play, _ctx, state) do
-   {[playback: :playing], state} 
- end

+ @impl true 
+ def handle_setup(_ctx, state) do
+   Process.send_after(self(), :play, 1000)
+   {[setup: :incomplete], state}
+ end
+
+ @impl true
+ def handle_info(:play, _ctx, state) do
+   {[setup: :complete], state}
+ end
```

`:setup` action is available not only in pipelines but in bins and elements as well.