Getting type error undefined object in react native?

Question

I am trying to output the data inside render() but I am getting error why so ?

Code:

render() {

        let marketing_plan_projects = [];

        marketing_plan_projects = this.props.markets.data ? this.props.markets.data : null;
        let marketing_updates = get_marketing_updates_from_projects(marketing_plan_projects);

        console.log(marketing_updates);

        return (
            <ScrollView style={styles.container}>

                <Text>{marketing_updates[0].project_name}</Text>

            </ScrollView>
        );
    }

I also tried this: (still gives error)

<Text>{marketing_updates ? marketing_updates[0].project_name: ""}</Text>

console.log(marketing_updates) is :

I am getting following error:

@R.Duteil Initially it is empty(see in screenshot) but then re rendering happens so it gets populated. — fun joker
– fun joker, Commented Oct 1, 2018 at 9:51
Your error is thrown because at first you have an empty array. react-native can't know that at some point you will actually have data there. You could do what you have already tried with some modifications: <Text>{marketing_updates && marketing_updates.length > 0 ? marketing_updates[0].project_name: ""}</Text> — Andrei Olar
– Andrei Olar, Commented Oct 1, 2018 at 9:58

R.Duteil · Accepted Answer · 2018-10-01 09:55:31Z

2

This line :

marketing_updates ? marketing_updates[0].project_name: ""

does not test if the array is empty, but just if it exists. Testing marketing_updates = [] will return true, as it is a truthy value.

See here for more informations : https://developer.mozilla.org/en-US/docs/Glossary/Truthy

Thus you can have an existing array but an undefined value for marketing_updates[0] as it might be empty.

To avoid your error, try this instead:

marketing_updates.length != 0 ? marketing_updates[0].project_name: ""

answered Oct 1, 2018 at 9:55

R.Duteil

1,2371 gold badge14 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

fun joker Over a year ago

If I want to inject the data into FlatList how can I do that ? Is this correct -> data={marketing_updates && marketing_updates.length > 0 ? marketing_updates[0].project_name: null }

R.Duteil Over a year ago

This will send marketing_updates' first element's project_name if there is at least one element, null otherwise as data.

fun joker Over a year ago

So I am just asking is this correct way -> data={marketing_updates && marketing_updates.length > 0 ? marketing_updates[0].project_name: null } to pass data to FlatList considering the situation in my question.

R.Duteil Over a year ago

It depends on what you need to pass as data to your FlatList. If you need the project_name of the first element, then yes, it is the correct way

fun joker Over a year ago

Check this question -> stackoverflow.com/questions/52589997/…

Collectives™ on Stack Overflow

Getting type error undefined object in react native?

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related