Objective C: switch inside loop - how to avoid (potential) memory leak

Question

I have a for loop where at the beginning an NSObject "value" is declared and then a switch statement within "value" is actually created. "value" then can be an NSNumber, an NSDate, an NSData, an NSString or nil. This is the code:

for (int i = 0; i < self.columnCount; i++) {
  NSObject *value;
  switch (mysql_fields[i].type) {
    case ...
      ...
    case MYSQL_TYPE_LONG:
      value = [[NSNumber alloc] initWithInt:atoi(row[i])];
      /* [value autorelease]; */  // 2)
      break;
    case MYSQL_TYPE_DECIMAL:
      NSString *decimal = [[NSString alloc] initWithCString:(char *)row[i] encoding:NSUTF8StringEncoding];
      value = [[NSDecimalNumber alloc] initWithString:decimal];
      /* [value autorelease]; */  // 2)
      [decimal release];
      break;
    case ...
      ...
  } // end of switch
} end of for
Field *field = [[[Field alloc] initWithRecord:record] autorelease];
/* [value autorelease]; */  // 3)
[field setValue:value forKey:@"value"];
/* [value release]; */  // 4)

Now I don't know how to release "value". This is what I tried and the corresponding Xcode 4 "Analyzer" messages:

1. no release -> "potential leak"
2. [value autorelease] after alloc/init within each case statement -> "object sent autorelease too many times"
3. [value autorelease] directly before the last use -> "object sent autorelease too many times"
4. [value release] after the last use -> "Incorrect decrement of the reference count of an object not owned by the caller at this point"

Answer 1

Add autorelease only where allocating the object, remove the rest:

value = [[[NSNumber alloc] initWithInt:atoi(row[i])] autorelease];
// ....
value = [[[NSDecimalNumber alloc] initWithString:decimal] autorelease];

Answer 2

You are declaring value inside the for loop, so you have to release it AFTER the switch but INSIDE the for loop.

for (int i = 0; i < self.columnCount; i++)
{
    NSObject *value;
    switch (mysql_fields[i].type)
    {
        case ...
            ...
        case MYSQL_TYPE_LONG:
            value = [[NSNumber alloc] initWithInt:atoi(row[i])];
            break;
        case MYSQL_TYPE_DECIMAL:
            NSString *decimal = [[NSString alloc] initWithCString:(char *)row[i] encoding:NSUTF8StringEncoding];
            value = [[NSDecimalNumber alloc] initWithString:decimal];
            [decimal release];
            break;
        case ...
            ...
    }
    Field *field = [[[Field alloc] initWithRecord:record] autorelease];
    [field setValue:value forKey:@"value"];
    [value release];
}