异步/等待可能导致未处理的承诺拒绝

Question

In a ReactNative component, when I press a button I got the "Possible Unhandled Promise Rejection" error when I execute this function:

async onAdd(item) {
    try {
        const response = await fetch('url', {
            method: 'POST',
            headers: {
                'Accept': 'application/json',
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({
                event_id: item.id,
                event_type: item.event_type,
            })
        });
        const responseJson = await response.json();
    } catch (error) {
        error(error);
    }
}

I do not know why since its in a try / catch block.

UPDATED
This is the error function:

function error(value) {
    if (console) {
        console.error(value)
    }
}

Answer 1

The problem is you are redefining the symbol error here with the catch argument:

} catch (error) {
    error(error);
}

so that hides your error() function. Change to this (with different names for the two symbols):

} catch (err) {
    error(err);
}

So, when you try to call error(error) you're trying to execute a non-function which throws which causes onAdd() to reject the promise that the async function returns and you don't have a .catch() handler on that function call (because you didn't think it could reject). And, as long as your catch() handler is written so that it doesn't throw itself, then your promise won't reject, but your coding error was causing it to throw.

Answer 2

The async function itself also returns a Promise. A very effective way of what's rejecting, is to just add a .catch to the result of onAdd() . The actual error should immediately pop up

Answer 3

调用此函数的方法也应该处理错误，可能在您的React类上