NSPredicate unable to parse format string

Question

I can't see any problem with these line of code. Why can't it parse?

[NSPredicate predicateWithFormat:@"(username  CONTAINS[cd] %1$@) || "
                                  "(userId    CONTAINS[cd] %1$@) || "
                                  "(firstname CONTAINS[cd] %1$@) || "
                                  "(lastname  CONTAINS[cd] %1$@)", searchString]"

The Log doesn't help either.

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "(username CONTAINS[cd] %1$@) || (userId CONTAINS[cd] %1$@) || (firstname CONTAINS[cd] %1$@) || (lastname CONTAINS[cd] %1$@)"'

Edit 1:

Okay, it seems like predicateWithFormat doesn't understand "%1$@". I switch it to

[... predicateWithFormat:[NSString stringWithFormat:...]] // (same format as above)

It passed the line. But, the next problem is:

self.filteredUserList = [self.userList filteredArrayUsingPredicate:predicate];

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ valueForUndefinedKey:]: the entity User is not key value coding-compliant for the key "a".'

"a" is the keyword I entered in the searchTextBox. WUT?

I printed out the predicate in the debug console, looks nothing wrong:

username CONTAINS[cd] a OR userId CONTAINS[cd] a OR firstname CONTAINS[cd] a OR lastname CONTAINS[cd] a

Edit 2:

Okay, problem solved with this super ugly code:

[NSPredicate predicateWithFormat:@"(username  CONTAINS[cd] %@) || "
                                  "(userId    CONTAINS[cd] %@) || "
                                  "(firstname CONTAINS[cd] %@) || "
                                  "(lastname  CONTAINS[cd] %@)", searchString, searchString, searchString, searchString];

What if I want to expand the search field in the future? I've got to add more parameters? more ", searchString, searchString, searchString"?

SOLVED

Thanks to Ewan and Bannings, giving 2 options to my question. I tested both of them, and they worked liek a charm. Can someone explain the different between those two, and in which case should I use which option?

** NOTE **

Bannings' answer is alright, until my search string contains a single quote ', then the app crash. So I think use Ewan's one is better.

Answer 1

You can do this:

[[NSPredicate predicateWithFormat:@"(username CONTAINS[cd] $str) || ..."] predicateWithSubstitutionVariables:@{@"str": searchString}];