Value for title can not be cast from ReadablenativeMap to string

Question

Consider:

InsertDataToServer = () => {
  const { pinValue1 } = this.state;
  const { pinValue2 } = this.state;
  const { pinValue3 } = this.state;
  const { pinValue4 } = this.state;
  var String_3 = pinValue1.concat(" ", pinValue2);
  var String_4 = String_3.concat(" " , pinValue3);
  var String_5 = String_4.concat(" " , pinValue4);

  fetch("http://www.aonde.biz/mobile/doLogin.php", {
    method: "POST",
    headers: {
      Accept: "application/json",
      "Content-Type": "application/json"
    },
    body: JSON.stringify({
      "pin": 212,
    })
  })
    .then(response => response.json())
    .then(responseJson => {
      // Showing the response message coming from
      // the server after inserting records.
      Alert.alert(responseJson);
    })
    .catch(error => {
      console.error(error);
    });

In the above code, when I pass the "pin" parameter API, it shows this error:

How can I resolve this issue?

score 33 · Answer 1 · edited May 29 '22 at 10:53

33

This error was fixed when the code changed from:

Alert.alert('Error:', error)

to:

Alert.alert('Error:', error.message)

edited May 29 '22 at 10:53

Peter Mortensen

30,738
21
105
131

answered Sep 04 '19 at 03:29

Bill Zelenko

2,606
1
17
26

What is the explanation for it? Please respond by [edit]ing (changing) your question/answer, not here in comments (***without*** "Edit:", "Update:", or similar - the answer should appear as if it was written today). – Peter Mortensen May 29 '22 at 10:54

score 9 · Answer 2 · edited May 29 '22 at 10:53

9

In your Alert.alert(responseJson);, you need to stringify it like this:

Alert.alert(JSON.stringify(responseJson));

Keep in mind that alert is a component from the mobile app, so it might not understand the code shown there is JSON content. If that doesn't work, use responseJson.text().

edited May 29 '22 at 10:53

Peter Mortensen

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21
105
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answered Jul 21 '19 at 23:50

Nicolas Silva

566
1
10
28

score 2 · Answer 3 · answered Jan 21 '20 at 17:03

2

Make sure your alerts are displaying the error.MESSAGE and not the whole error. Depending on the error and its type that might be the cause!

That was the cause of my issue.

answered Jan 21 '20 at 17:03

Marlon Englemam

351
5
11

1

Of course, this was my issue. I have passed error instead of error.message – Kaveen Hyacinth May 06 '21 at 15:49
1

yes, I remember I spent hours trying to figure out what the problem was lol. – Marlon Englemam May 31 '21 at 13:23

score 0 · Answer 4 · edited May 29 '22 at 10:58

0

The error was fixed when adding the title in the Alert method.

As in the documentation, the title of Alert must be given while calling the Alert method.

edited May 29 '22 at 10:58

Peter Mortensen

30,738
21
105
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answered Nov 26 '19 at 07:16

Ömer

188
2
11

Can you link to the documentation (non-naked link)? – Peter Mortensen May 29 '22 at 10:58

score 0 · Answer 5 · edited May 29 '22 at 11:00

0

I have had a similar issue. I solved it by changing one of the syntax. In your case, try this:

fetch("http://www.aonde.biz/mobile/doLogin.php",
  method: "POST",
  header: {
    Accept: "application/json",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "pin":212,

  })
)

What I changed to your coding: I removed {} after the URL.

If you get a red line error on the :, then remove method: header: and body: as well. The code will be like this:

fetch("http://www.aonde.biz/mobile/doLogin.php",
  "POST",
  {
    Accept: "application/json",
    "Content-Type": "application/json"
  },
  JSON.stringify({
    "pin":212,

  })
)

edited May 29 '22 at 11:00

Peter Mortensen

30,738
21
105
131

answered Sep 17 '21 at 14:32

Lolz

51
1
2

Re *"I removed {} after the URL."*: ***Why*** does that work? What is the explanation? From [the Help Center](https://stackoverflow.com/help/promotion): *"...always explain why the solution you're presenting is appropriate and how it works"*. Please respond by [edit]ing (changing) your answer, not here in comments (***without*** "Edit:", "Update:", or similar - the answer should appear as if it was written today). – Peter Mortensen May 29 '22 at 11:02

score 0 · Answer 6 · answered Sep 22 '22 at 18:04

0

You can check if its string before sending it to Alert.alert method:

const title = "Error title..";
const errorMessage = (typeof error === 'string' || error instanceof String) ? error : error.message;
Alert.alert(title, errorMessage);

answered Sep 22 '22 at 18:04

Danny Michaeli

150
3

score -1 · Answer 7 · answered Apr 06 '21 at 20:51

-1

I was having this error because I installed a library that needed me to compile the app again and I hadn't compiled it.

After compiling again everything worked fine.

answered Apr 06 '21 at 20:51

Igor Ribeiro

59
2

score -2 · Accepted Answer · answered Oct 25 '18 at 18:05

-2

You can simply remove double quotation marks from pin.

fetch("http://www.aonde.biz/mobile/doLogin.php", {
  method: "POST",
  headers: {
    Accept: "application/json",
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    pin:212,
  })
})

answered Oct 25 '18 at 18:05

Samitha Nanayakkara

2,529
2
10
23

I don't understand why you are only adding 212 as your pin even after you concatenate all the strings. However when I check with given URL and body as I suggested, I got status:1 output. I don't understand why you are saying the issue is occurring. If you can be more elaborate, I can help you. – Samitha Nanayakkara Oct 26 '18 at 16:40
can you share your code through you can get status 1? Thank you – Atul Tiwari Oct 27 '18 at 10:33
I got the Status 1 using postman. But with the method I used in this answer, I did not get the error you are saying because you don't have to put key in double quotes when you are using stringify. Only the value if it is not numeric. – Samitha Nanayakkara Oct 28 '18 at 12:22

Value for title can not be cast from ReadablenativeMap to string

8 Answers8