I'm new to React, I'm having trouble rendering my app due to this error. It's seems the data that I'm trying to render as elements won't render due to trying to set state when unmounted?

I'm not sure how I'm getting this error, as I'm setting the state of Data in ponentDidMount.

How can I fix this issue?

error: attempted to update ponent that has already been unmounted (or failed to mount)

class Profile extends React.PureComponent {
  static propTypes = {
    navigation: PropTypes.object,
    handleLogout: PropTypes.func,
    user: PropTypes.object,
  };

  static navigationOptions = {
    headerVisible: true,
    title: 'Profile',
  };

constructor(props) {
    super(props);

    this.state = {
    data: [],
    loading: true

    };
  }

ponentDidMount() {

  fetch(":8080/bined", { method: 'get' })
    .then(response => response.json())
    .then(data => {
      this.setState({data: data,});

    })
   .catch(function(err) {
     // 
   })
}

 render() {

    const { user } = this.props;
    let email;

    if (user) {
      email = user.rows[0].ACCTNO;
    }
    return (
      <ContentWrapper>
        <View style={styles.container}>
          <Image style={styles.header} source={images.profileHeader} />
          <View style={styles.body}>
            <Avatar email={email} style={styles.avatar} />
             {
   this.state.data.map(function(rows, i){
         this.setState({mounted:  true});

    return(
      <View key={i}>
        <Text>{rows.FIRSTNAME}</Text>
      </View>
    );
  })
}            <Text style={styles.email}>{_.capitalize(email)}</Text>

            <Button
              title="Log out"
              icon={{ name: 'logout-variant', type: 'material-munity' }}
              onPress={this.logout}
              style={styles.logoutButton}
            />
          </View>
        </View>
      </ContentWrapper>
    );
  }
}

export default Profile;

I'm new to React, I'm having trouble rendering my app due to this error. It's seems the data that I'm trying to render as elements won't render due to trying to set state when unmounted?

I'm not sure how I'm getting this error, as I'm setting the state of Data in ponentDidMount.

How can I fix this issue?

error: attempted to update ponent that has already been unmounted (or failed to mount)

class Profile extends React.PureComponent {
  static propTypes = {
    navigation: PropTypes.object,
    handleLogout: PropTypes.func,
    user: PropTypes.object,
  };

  static navigationOptions = {
    headerVisible: true,
    title: 'Profile',
  };

constructor(props) {
    super(props);

    this.state = {
    data: [],
    loading: true

    };
  }

ponentDidMount() {

  fetch("http://10.0.2.2:8080/bined", { method: 'get' })
    .then(response => response.json())
    .then(data => {
      this.setState({data: data,});

    })
   .catch(function(err) {
     // 
   })
}

 render() {

    const { user } = this.props;
    let email;

    if (user) {
      email = user.rows[0].ACCTNO;
    }
    return (
      <ContentWrapper>
        <View style={styles.container}>
          <Image style={styles.header} source={images.profileHeader} />
          <View style={styles.body}>
            <Avatar email={email} style={styles.avatar} />
             {
   this.state.data.map(function(rows, i){
         this.setState({mounted:  true});

    return(
      <View key={i}>
        <Text>{rows.FIRSTNAME}</Text>
      </View>
    );
  })
}            <Text style={styles.email}>{_.capitalize(email)}</Text>

            <Button
              title="Log out"
              icon={{ name: 'logout-variant', type: 'material-munity' }}
              onPress={this.logout}
              style={styles.logoutButton}
            />
          </View>
        </View>
      </ContentWrapper>
    );
  }
}

export default Profile;

• javascript
• reactjs
• react-native

• 1 Your map function is why the error is occurring. You call setState inside render(). – Alex Harrison Commented May 17, 2017 at 18:01

4 Answers 4

In your render function, you're calling this.setState({mounted:true}). From React's ponent documentation:

The render() function should be pure, meaning that it does not modify ponent state, it returns the same result each time it's invoked, and it does not directly interact with the browser.

Here's the link to the React documentation on the render function.

There is another way this error can occur...thinking that props are individual arguments (props is actually a single argument)

import React from 'react';

const Posts = posts => {       // WRONG

const Posts = ({posts}) => {   // RIGHT
  const renderPosts = () => {
    return posts.map(post => <div>{post.title}</div>);
  };

  return <div>{renderPosts()}</div>;
};

My problem is I forget

import React from 'react'

in my .jsx file, since I thought importing React is not needed in functional ponent.

My problem was in Sider, Then inside Link tag I did misspell instead of /location I wrote /locaion .

 <Menu.Item key="2">
      <Icon type="settings" />
      <span><Link style={styles.linkStyle} to="/locations">Locations</Link></span>
    </Menu.Item>