NSNumber unrecognized selector - ios

Question

The following code
NSMutableString *a = [[NSMutableString alloc] init];
NSMutableString *pivot =[[NSMutableString alloc] init];
int i= 0;
for ( i = 0; i < [columns count]; i++)
{
if ([[[data objectForKey:pivot] class] isKindOfClass:[NSNumber class]])
{
sqlite3_bind_int(sqlStatement, i+1,[[columns objectAtIndex:i] integerValue]);
}
else
{
// NSLog(#"kind of class %# %#",NSStringFromClass([[data objectForKey:pivot] class]) ,[data objectForKey:pivot]);
[pivot setString:[columns objectAtIndex:i]];
[a setString:(NSString*)[data objectForKey:pivot]];
sqlite3_bind_text(sqlStatement, i+1, [a UTF8String], -1, 0);
}
}
a = nil;
pivot = nil;
raises an exception
kind of class __NSCFConstantString
-[__NSCFNumber length]: unrecognized selector sent to instance 0xc94c240
But the log clearly says that [data objectForKey:pivot] is a String! And the test variable is always 0!
I checked in the debug and actually [data objectForKey:pivot] is a Number. And in fact I use an if (not shown) to check if it is a number or not. Obviously, the if fails...

Answer 1

You are casting the class to a string when you try to format it this way, try to get the string name from the class with NSStringFromClass(class) :
id pivotObject = [data objectForKey:pivot];
NSLog(#"kind of class %#", NSStringFromClass([pivotObject class]));
if ([pivotObject isKindOfClass:[NSString class]]) {
[pivot setString:[columns objectAtIndex:i]];
[a setString:pivotObject];
}
Also the isKindOfClass: returns a BOOL not int.
But most importantly:
I think the error in the [pivot setString:[columns objectAtIndex:i]] line, since here you change the pivot variable and then retrieve it from data, But since the pivot variable is changed you request a different key from the data dictionary. This you will get an other value. My code I only grab the pivotData once from data.