仅在数据存在时渲染 FlatList

Question

I run a graphql query and depending on the data, render a flatList.

  const { data, error } = useGetMyProfileQuery({
    //onCompleted: _onCompleted,
    onError: _onGetMyProfileQueryError,
  });
....
return (
    <SafeAreaView style={styles.safeView}>
      <Container style={styles.container}>
        <View style={styles.listHolder}>
          <FlatList
            data={data ? data.me.friends : null}
            horizontal={false}
            renderItem={({ item }) => (
              <Friend
                friend={item}
                onDeleteFriend={onDeleteFriend}
                originatorId={data ? data.me.id : null}
              />
            )}
            keyExtractor={(data: any) => '3'}
            ListEmptyComponent={renderEmptyContainer()}
          />
        </View>
      </Container>
    </SafeAreaView>
  );
};

However, currently, I have to use ternary operators for checks like data? data.me.friends: null data? data.me.friends: null in the FlatList to avoid Typescript errors. If the query fails, and the data is null, It disturbs the whole performance and I will have to use multiple if-else within the whitelist item component too.

So I am looking for the best way such that data is passed into the Flatlist only when the mutation is successful. I could use onCompleted for that but I am not sure how to organize it such that no flat list is displayed from the main return when there's an error.

Also, currently, I am using the same key for all elements of the list but it shouldn't be like that obviously

Answer 1

Render your list when you have data, In this way, you will also have better performance when lesser things are rendered so it will be a conditional rendering of your Flatlist .

{data && data.me && data.me.friends.lenght > 0 &&
    <FlatList
        data={data.me.friends}
        horizontal={false}
        renderItem={({ item }) => (
          <Friend
            friend={item}
            onDeleteFriend={onDeleteFriend}
            originatorId={data ? data.me.id : null}
          />
        )}
        keyExtractor={(data: any) => '3'}
        ListEmptyComponent={renderEmptyContainer()}
      />
}

Answer 2

Did you tried data={data?.me?.friends}

You can also use this syntax data={data? data?.me?.friends: []} data={data? data?.me?.friends: []}

Answer 3

You have to used as

<SafeAreaView style={styles.safeView}>
  <Container style={styles.container}>
    <View style={styles.listHolder}>
      <FlatList
        data={data?.me?.friends || []}
        horizontal={false}
        renderItem={({ item }) => (
          <Friend
            friend={item}
            onDeleteFriend={onDeleteFriend}
            originatorId={data ? data.me.id : null}
          />
        )}
        keyExtractor={(data: any) => '3'}
        ListEmptyComponent={renderEmptyContainer()}
      />
    </View>
  </Container>
</SafeAreaView>

data={data?.me?.friends || []} you have to use this that I have already mentioned in the code https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining This link will also useful