React-native - Passing data from one screen to another

Question

I am trying to learn how to use react-native, so I am putting up a small app that fetch a list of users from a server, displays it in a listview and where pressing a row opens a screen displaying user's data.

I set up a navigator to go from one screen to another. When pressing on the row I am able to open a new screen but I can't figure how to pass data to this new screen.

I set up an navigator in index.android.js

import React from 'react';
import {
  AppRegistry,
  Navigator,
} from 'react-native';

import ContactList from './src/containers/ContactList.js';

function MyIndex() {
  return (
    <Navigator
      initialRoute={{ name: 'index', component: ContactList }}
      renderScene={(route, navigator) => {
        if (route.component) {
          return React.createElement(route.component, { navigator });
        }

        return undefined;
      }}
    />
  );
}

AppRegistry.registerComponent('reactest', () => MyIndex);

First I display a screen with a button and an empty listview (ContactList.js), after pressing the button, I fetch some JSON data that are used to update the listview :

import React, { Component, PropTypes } from 'react';
import {
  Text,
  View,
  TouchableOpacity,
  TouchableHighlight,
  ListView,
  Image,
} from 'react-native';

import styles from '../../styles';
import ContactDetails from './ContactDetails';

const url = 'http://api.randomuser.me/?results=15&seed=azer';

export default class ContactList extends Component {
  static propTypes = {
    navigator: PropTypes.object.isRequired,
  }
  constructor(props) {
    super(props);

    const datasource = new ListView.DataSource({ rowHasChanged: (r1, r2) => r1 !== r2 });
    this.state = {
      jsonData: datasource.cloneWithRows([]),
      ds: datasource,
    };
  }
  _handlePress() {
    return fetch(url)
      // convert to json
      .then((response) => response.json())
      // do some string manipulation on json
      .then(({ results }) => {
        const newResults = results.map((user) => {
          const newUser = {
            ...user,
            name: {
              title: `${user.name.title.charAt(0).toUpperCase()}${user.name.title.slice(1)}`,
              first: `${user.name.first.charAt(0).toUpperCase()}${user.name.first.slice(1)}`,
              last: `${user.name.last.charAt(0).toUpperCase()}${user.name.last.slice(1)}`,
            },
          };

          return newUser;
        });

        return newResults;
      })
      // set state
      .then((results) => {
        this.setState({
          jsonData: this.state.ds.cloneWithRows(results),
        });
      });
  }
  renderRow(rowData: string) {
    return (
      <TouchableHighlight
        onPress={() => {
          this.props.navigator.push({
            component: ContactDetails,
          });
        }}
      >
        <View style={styles.listview_row}>
          <Image
            source={{ uri: rowData.picture.thumbnail }}
            style={{ height: 48, width: 48 }}
          />
          <Text>
            {rowData.name.title} {rowData.name.first} {rowData.name.last}
          </Text>
        </View>
      </TouchableHighlight>
    );
  }
  render() {
    const view = (
      <View style={styles.container}>
        <TouchableOpacity
          onPress={() => this._handlePress()}
          style={styles.button}
        >
          <Text>Fetch results?</Text>
        </TouchableOpacity>
        <ListView
          enableEmptySections
          dataSource={this.state.jsonData}
          renderRow={(rowData) => this.renderRow(rowData)}
          onPress={() => this._handleRowClick()}
        />
      </View>
    );

    return view;
  }
}

When a row is pressed, it opens a new screen ContactDetails.js, which is supposed to display user's data :

import React, {
} from 'react';

import {
  Text,
  View,
} from 'react-native';

import styles from '../../styles';

export default function ContactDetails() {
  return (
    <View style={styles.container}>
      <Text>{this.props.title}</Text>
      <Text>{this.props.first}</Text>
      <Text>{this.props.last}</Text>
    </View>
  );
}

At this point I got this error :

undefined is not an object (evaluating 'this.props.title')

I have tried many things such as :

this.props.navigator.push({
    component: ContactDetails,
    title: rowData.name.title,
    first: rowData.name.first,
    last: rowData.name.last,
});

or

this.props.navigator.push({
    component: ContactDetails,
    props: {
        title: rowData.name.title,
        first: rowData.name.first,
        last: rowData.name.last,
    }
});

or

this.props.navigator.push({
    component: ContactDetails,
    passProps: {
        title: rowData.name.title,
        first: rowData.name.first,
        last: rowData.name.last,
    }
});

But to no avail.

I also read that I should use redux. Am I doing something wrong ?

EDIT: The problem is here :

<TouchableHighlight
    onPress={() => {
      this.props.navigator.push({
        component: ContactDetails,
      });
    }}
>

I assume I should pass some parameters there, but whatever I tried above failed.

Answer 1

So the problem seems to lie here:

<Navigator
  initialRoute={{ name: 'index', component: ContactList }}
  renderScene={(route, navigator) => {
    if (route.component) {
      return React.createElement(route.component, { navigator });
    }

    return undefined;
  }}
/>

In the renderScene function, you do receive the route (and use route.component) but you don't pass your route.props or route.passProps or what ever you want to call it! And from what I see in the source of Navigator at that moment you should have the full route object as you created it. So you should be able to pass your props along.

For example:

<Navigator
  initialRoute={{ name: 'index', component: ContactList }}
  renderScene={(route, navigator) => {
    if (route.component) {
      return React.createElement(route.component, { navigator, ...route.props });
    }

    return undefined;
  }}
/>

// push
<TouchableHighlight
  onPress={() => {
    this.props.navigator.push({
      component: ContactDetails,
      props: { /* ... */ }
    });
  }}
>

You could also setup redux, but that's not a requirement. Though if your app gets bigger you should really consider using an external store!

---

Update:

There is also another problem.

You use a functional components. Functional components don't have a this. They receive the props in parameter.

So it should be like this:

export default function ContactDetails(props) {
  return (
    <View style={styles.container}>
      <Text>{props.title}</Text>
      <Text>{props.first}</Text>
      <Text>{props.last}</Text>
    </View>
  );
}

Answer 2

I still feel the default navigation is to cumbersome. I highly suggest using this library for routing: https://github.com/aksonov/react-native-router-flux

Answer 3

Replace code :

<TouchableOpacity
      onPress={() => this._handlePress()}
      style={styles.button}
>

With :

<TouchableOpacity
      onPress={() => this._handlePress()}
      style={styles.button}
     navigator={navigator} {...route.props}
>

This is fine:

this.props.navigator.push({
component: ContactDetails,
   props: {
    title: rowData.name.title,
    first: rowData.name.first,
    last: rowData.name.last,
  }
});