objective c - Xcode process launch failed: invalid host string: '(null)' -

i trying learn objective c. however, when write code , run it, xcode says build sucsessful code not run. comes saying:

process launch failed: invalid host string: '(null)'

please help.

i have reinstalled it.

xcode error invalid string localhost

open terminal , type

sudo nano /etc/hosts

if asks password ,enter password;

copy , paste commands

127.0.0.1       localhost 255.255.255.255 broadcasthost ::1             localhost  fe80::1%lo0     localhost

then press

control-o

and press

enter

and press

control-x

then type

  dscacheutil -flushcache

thats !!!!

WIKI