React Native – Warning: Each child in a list should have a unique "key" prop

I am listing products by using FlatList in the app. I have Products.js, ProductCard.js.

Products.js:

const Products = ({navigation}) => {

  const renderItem = ({item}) => (
    <ProductCard
      item={item}
      onClickHandler={() => navigation.navigate('Item Detail', {item: item})}
    />
  );

  return (
    <View>
      <ProductOperations />
      <FlatList
        data={data}
        keyExtractor={item => item.id.toString()}
        renderItem={renderItem}
      />
    </View>
  );
};

export default Products;

ProductCard.js:

const ProductCard = props => {
  const createStars = rating => {
    //...logic
  };

  return (
    <TouchableOpacity key={props.item.id} style={styles.card} onPress={props.onClickHandler} >
      <Image style={styles.image} source={{uri: props.item.thumbnail}} />
      <View style={styles.textColumn}>
        <Text style={[styles.brandText, styles.textPadding]}>
          {props.item.brand}
        </Text>
        <Text style={[styles.titleText, styles.textPadding]}>
          {props.item.title}
        </Text>
      </View>
      <View style={styles.textColumn}>
        <View style={[styles.textColumn, styles.textPadding]}>
          {createStars(props.item.rating)}
        </View>
        <Text style={[styles.ratingText, styles.textPadding]}>
          {props.item.rating}
        </Text>
      </View>
      <Text style={[styles.priceText, styles.textPadding]}>
        ${props.item.price}
      </Text>
    </TouchableOpacity>
  );
};

export default ProductCard;

I have keyExtractor on the FlatList, and key on the ProductCard. But I get warning:

Warning: Each child in a list should have a unique "key" prop.

Check the render method of `ProductCard`. See https://reactjs.org/link/warning-keys for more information.
    at Icon (http://localhost:8081/index.bundle?platform=android&dev=true&minify=false&app=com.shoppingapp&modulesOnly=false&runModule=true:101233:38)

How can I solve this? What should I change?

>Solution :

It means you need to have a key for elements created inside an array, which I believe comes from createStars, sample solution:

const createStars = (rating) => {
    return [1, 2, 3, 4, 5].map((val) => <Star key={val} selected={val <= rating}>);
};