# Disallow usage of setState in componentWillUpdate (`reblend/no-will-update-set-state`)

<!-- end auto-generated rule header -->

Updating the state during the componentWillUpdate step can lead to indeterminate component state and is not allowed.

## Rule Details

Examples of **incorrect** code for this rule:

```jsx
var Hello = createReblendClass({
  componentWillUpdate: function () {
    this.setState({
      name: this.props.name.toUpperCase(),
    });
  },
  render: function () {
    return <div>Hello {this.state.name}</div>;
  },
});
```

Examples of **correct** code for this rule:

```jsx
var Hello = createReblendClass({
  componentWillUpdate: function () {
    this.props.prepareHandler();
  },
  render: function () {
    return <div>Hello {this.props.name}</div>;
  },
});
```

```jsx
var Hello = createReblendClass({
  componentWillUpdate: function () {
    this.prepareHandler(function callback(newName) {
      this.setState({
        name: newName,
      });
    });
  },
  render: function () {
    return <div>Hello {this.props.name}</div>;
  },
});
```

## Rule Options

```js
...
"reblend/no-will-update-set-state": [<enabled>, <mode>]
...
```

### `disallow-in-func` mode

By default this rule forbids any call to `this.setState` in `componentWillUpdate` outside of functions. The `disallow-in-func` mode makes this rule more strict by disallowing calls to `this.setState` even within functions.

Examples of **incorrect** code for this rule:

```jsx
var Hello = createReblendClass({
  componentWillUpdate: function () {
    this.setState({
      name: this.props.name.toUpperCase(),
    });
  },
  render: function () {
    return <div>Hello {this.state.name}</div>;
  },
});
```

```jsx
var Hello = createReblendClass({
  componentWillUpdate: function () {
    this.prepareHandler(function callback(newName) {
      this.setState({
        name: newName,
      });
    });
  },
  render: function () {
    return <div>Hello {this.state.name}</div>;
  },
});
```