Initialize Objective-C tye in Objective-C++ class -

i need initialize instance of objective-c sdk ("portsipsdk") this:

sdkinstance = [[portsipsdk alloc] init]; 

however, need in objective-c++ class, , xcode complains above line of code:

undefined symbols architecture armv7:   "_objc_class_$_portsipsdk", referenced from:       objc-class-ref in libcore-d.a(csipclientiosimpl.mm.o) ld: symbol(s) not found architecture armv7 clang: error: linker command failed exit code 1 (use -v see invocation) 

"csipclientiosimpl.mm" name of file in class implemented.

if don't initialization, xcode doesn't complain, error happens when try call methods of sdk instance, presumably because never initialized.