ios - Exception in registering FFEngine -

i using ffengine playing video via rtmp. getting following exception:

__nscfstring objectfromjsonstring]: unrecognized selector sent instance 0xa039d80 on line registerffengine(@"yq2oibqrbxoo35vedico9ggf4arfxrdjq3yiivbltwipe/sgphrthjevczt6mtafejcym1fkbddy+we8j7oejlk+u1keo7igfedq+krnsnc=")

i don't know whether registration key incorrect or there other issue. need help.

when use ffengine framework , have add “-objc” in project. below simple step add “-objc” in project :

1) select project file project navigator on far left side of window.

2) select target want add linker flag.

3) select “build settings” tab

4) choose “all” show build settings.

5) scroll down “linking” section, , double-click right of says “other linking flags”.

6) box appear, click on “+” button add new linker flag.

7) type “-objc” (no quotes) , press enter.

when add -objc after error solved.