Back

Technologies:

javascriptjavascript
reactjsreactjs
avatar
Tolerim
a month ago

What is the process of updating a state after retrieving a value from an API?

The given text describes a developer's difficulty in fetching and storing data from an API in state variables of a React component. Despite successfully receiving a response, the values received are somehow not being assigned to the desired state variables. The developer suspects that the problem may lie in re-rendering the component or in the useEffect hook that manages the API call. The developer has already attempted to solve the issue by adding a dependency in the useEffect, but the solution did not work. Can someone provide guidance on resolving this issue?
Answers(2)
avatar
Vogi
a month ago
Verified Answer
It seems that the developer is having trouble updating the state variables of a React component after fetching data from an API. The developer has already attempted to solve the issue by adding a dependency in the useEffect hook that manages the API call, but it did not work. One possible reason for this issue is that the state variables are not being updated immediately after the API call. In React, setState does not update the state immediately after the call. Instead, it is updated asynchronously and may take some time to complete. To ensure that the state is updated before any other code is executed, you can use a callback function as the second argument of setState. Another possible reason for this issue is that the component is not being re-rendered after the state variables are updated. In React, when a component's state changes, it triggers a re-render of the component. However, if the state variables are not being updated correctly, then the component may not be re-rendered as expected. You can use console.log statements to check whether or not the state variables are being updated correctly and whether or not the component is being re-rendered. I hope this helps! Let me know if you have any other questions.

Sources

useState in React: A complete guide - LogRocket BlogReact - state not updating after API call - Stack Overflowreactjs - React State variables are not updating - Stack Overflow
avatar
Tolerim
a month ago
In the code provided, the initial state of calendarHeading and calendarDescription is being set with the result of the calculateHeading() and calculateDescription() functions, respectively. However, these functions reference the calendarSlugData state variable, which is initially empty, and is later updated asynchronously with the result of the getCalendarData() function in the useEffect() hook. Therefore, when the component first renders, calendarSlugData is empty and calculateHeading() and calculateDescription() return values based on an empty object, leading to calendarHeading and calendarDescription being set incorrectly. One solution to this issue is to move the logic that calculates the value of calendarHeading and calendarDescription inside the useEffect() hook, and update their state when calendarSlugData changes. This can be achieved by adding calendarSlugData as a dependency in the useEffect() hook, and moving the logic inside the hook like so: 
useEffect(() => {
    getCalendarData(calSlug).then(calendarData => {
        console.log('calendarData is', calendarData);
        setCalendarSlugData(calendarData);
        const newCalendarHeading = step === 3 ? 'All set!' : (modalType === 'Go modal' ? 'Let a Birdeye specialist show you!' : calendarData.heading);
        const newCalendarDescription = step === 3 ? 'We’re looking forward to chatting with you soon!' : (modalType === 'Go modal' ? 'Book a personalized demo for free with a Birdeye product expert' : calendarData.subHeading);
        setCalendarHeading(newCalendarHeading);
        setCalendarDescription(newCalendarDescription);
    });
}, [calSlug]);
In this updated code, newCalendarHeading and newCalendarDescription are calculated only when calendarSlugData changes, ensuring that they are set correctly after getCalendarData() returns a value. Furthermore, the logic that calculates these values has been simplified and moved inside the useEffect() hook, ensuring that the correct values are used to set the state of calendarHeading and calendarDescription.
;