How to handle '[<__NSCFString 0x2f1730> valueForUndefinedKey:]: this class is not key value coding-compliant for the key $oid' error

Question

I am hitting the error (stated in the subject) because there are times the property 'id' does not store the hash containing '$oid' in the returned json. For example

Sometimes I get:

"id":{"$oid":"4eea972209f47a0028000140"}

Some other times I get

"id":"4eea972209f47a0028000140"

I am trying to do a check in the following code to cater for such irregularity

if ([[question valueForKey:@"id"] valueForKey:@"$oid"])
{
    question_id = [[question valueForKey:@"id"] valueForKey:@"$oid"];
}
else
{
    question_id = [question valueForKey:@"id"];
}

However, it still doesn't work as the code fails during the checking phase.

How can I implement a check so that I will take question_id from '$oid' only if it exists?

Looks like its a API provided by a mongo DB back end - whoever is responsible for the API should really fix that…. — Tony Million, Jan 06 '12 at 08:24

score 5 · Accepted Answer · answered Jan 06 '12 at 07:56

5

Try the following code.

id quesDict = [question valueForKey:@"id"];
if( [quesDict isKindOfClass:[NSDictionary class]] )
{
    question_id = [quesDict valueForKey:@"$oid"];
}
else
{
    question_id = quesDict;
}

answered Jan 06 '12 at 07:56

Ilanchezhian

17,426
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1

I answered in prose, you gave the same in code! We should merge them to make one super-answer :) – jrturton Jan 06 '12 at 08:02

score 3 · Answer 2 · answered Jan 06 '12 at 07:59

3

You need to check what type is being returned by [question valueForKey:@"id"], it looks like sometimes it is a string, and sometimes it is another object which is KVC compliant for your other key. Your error will be in the very first if statement.

answered Jan 06 '12 at 07:59

jrturton

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How to handle '[<__NSCFString 0x2f1730> valueForUndefinedKey:]: this class is not key value coding-compliant for the key $oid' error

2 Answers2

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