layout sider will render twice on first load

Version

antd 3.1.0 react 16.2.0

Environment

chrome

Reproduction link

class MySider extends Component {
  render() {
    console.log('sider')
    return <Sider>Sider</Sider>
  }
}

class App extends Component {
  render() {
    return (
      <Layout>
      <Header>Header</Header>
      <Layout>
        <MySider></MySider>
        <Content>Content</Content>
      </Layout>
      <Footer>Footer</Footer>
    </Layout>



    );
  }
}

Steps to reproduce

When first load, Snippets above will print sider twice

What is expected?

print sider only once

What is actually happening?

When first load, Snippets above will print sider twice

[jiacai2050]

because we register Sider to Layout by adding it to state.

I can’t really understand this. If this action will cause rerender, why can’t implement Sider in other way, which cause no rerender.

For me as an user, rerender is the last thing I want.

[yesmeck]

use this method to detect Sider ant-layout-has-sider class is added to layout only after rerendering because we register Sider to Layout by adding it to state.