Xcode compilation errors with external library (OSX program) - objective-c

Question

I have a simple "Hello world" type program in Xcode and I'm trying to use an external library in that, but I'm getting compilation errors. The library is the Magtek edynamo macOS sdk:
https://www.magtek.com/Content/SoftwarePackages/1000004036.zip
(parent page is https://www.magtek.com/support/edynamo?tab=software; download is the macOS SCRA SDK)
This is my code:
#import "MTSCRA.h"
int main (int argc, const char * argv[])
{
MTSCRA* mtSCRALib = [[MTSCRA alloc] init];
return 0;
}
So basically I'm just importing the library and trying to instantiate one of its classes. Xcode doesn't show any inline compile errors anywhere, but when I try to build and run, it results in a variety of undefined symbol errors such as this:
Undefined symbols for architecture x86_64:
"_NSApplicationWillTerminateNotification", referenced from:
-[HIDManager init] in libMTSCRAOSX.a(HIDManager.o)
and warnings such as this:
ld: warning: object file (/path/HelloWorld/libMTSCRAOSX.a(MTSCRA.o)) was built for newer OSX version (10.12) than being linked (10.11)
(If I comment out the MTSCRA* mtSCRALib = [[MTSCRA alloc] init]; line, it runs fine.)
These are the steps I took to include the library in my Xcode project:
I dropped the MTSCRA.h and libMTSCRAOSX.a into my project directory.
From Build phases -> Link binary, I added libMTSCRAOSX.a.
Build Settings -> Library search paths is set to "$(inherited)" and "$(PROJECT_DIR)/HelloWorld"
This is my environment:
Macbook Pro 64-bit
OSX El Capitan 10.11.5
Xcode V8.2.1
Tried all the google solutions; nothing worked. Any help...can anyone else successfully import and use this library?

Answer 1

Solved this. Not sure if these are rookie mistakes, but I had two issues:
1) I also needed to include the library /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.‌​platform/Developer/S‌​DKs/MacOSX.sdk/usr/l‌​ib/libstdc++.6.0.9.t‌​bd
2) I also had to import #import <Cocoa/Cocoa.h>. So:
#import "MTSCRA.h"
#import <Cocoa/Cocoa.h>
int main (int argc, const char * argv[])
{
MTSCRA* mtSCRALib = [[MTSCRA alloc] init];
return 0;
}