Question

I set a breakpoint…

if I do:

(lldb) print [self dictionary]
(NSDictionary *) $5 = 0x0945c760 1 key/value pair

but if I do:

(lldb) print [[self dictionary] allKeys]
error: no known method '-allKeys'; cast the message send to the method's return type
error: 1 errors parsing expression

Even if I try to access the key that I know is in there..

(lldb) print [[self dictionary] objectForKey:@"foobar"]
error: no known method '-objectForKey:'; cast the message send to the method's return     type
error: 1 errors parsing expression

What am I doing wrong?

Answer 1

error: no known method '-objectForKey:'; cast the message send to the method's return type

So, it tells you it can’t deduce return type information merely from the name of the message send – and that’s perfectly fine. And it even tells you how exactly you have to resolve that problem – you have to cast the message send to the method’s return type.

Firing up Apple’s docs, we find out that - [NSDictionary objectForKey:] returns id – the generic Objective-C object type. Casting to id (or even better, if you know what types of objects your dictionary holds, casting to that exact object type) does the trick:

(lldb) print (MyObject *)[(NSDictionary *)[self dictionary] objectForKey:@"foobar"]