ios - Can't create global function in Objective - C -

i'm trying create global function in objective-c. created new .m , h. file subclass of viewcontroller.

this connection.m

#import "connection.h" @interface viewcontroller () <nsstreamdelegate>  @property (strong,nonatomic) nsinputstream * inputstream; @property (strong,nonatomic) nsoutputstream * outputstream;  @end  @implementation viewcontroller(connection) -(void)initnetworkcommunication {     cfreadstreamref readstream;     cfwritestreamref writestream;     cfstreamcreatepairwithsockettohost(null, (cfstringref)@"192.168.0.10", 35000, &readstream, &writestream);     self.inputstream = objc_unretainedobject(readstream);     self.outputstream = objc_unretainedobject(writestream);     [self.inputstream setdelegate:self];     [self.outputstream setdelegate:self];     [self.inputstream scheduleinrunloop:[nsrunloop currentrunloop] formode:nsdefaultrunloopmode];     [self.outputstream scheduleinrunloop:[nsrunloop currentrunloop] formode:nsdefaultrunloopmode];      [self.inputstream open];     [self.outputstream open]; } 

connection.h

#import "viewcontroller.h"  @interface viewcontroller(connection)  -(void)initnetworkcommunication;  @end 

viewcontroller.m

#import "viewcontroller.h" #import "connection.h"  @interface viewcontroller ()  @end  @implementation viewcontroller  - (void)viewdidload {     [super viewdidload];  }  - (void)didreceivememorywarning {     [super didreceivememorywarning];     // dispose of resources can recreated. } - (ibaction)connectionbutton:(id)sender {     [self initnetworkcommunication]; }  @end 

i tryed 3 methods mentioned in how create global functions in objective-c no 1 of 3 works. first two(create class method in static class , declare global function instead of class) don't work because when change "-(void)... +(void).. every "self..." gets error , same in second method. third 1 works me (adding category nsobject methods) when i'm trying call [self initnetworkcommunication] function program crashesh signal sigabrt , can't solve problem. ideas how can call function?

update: @gronzzz

connection.m  @interface viewcontroller () <nsstreamdelegate>  @property (strong,nonatomic) nsinputstream * inputstream; @property (strong,nonatomic) nsoutputstream * outputstream;  @end  @implementation connection  -(void)initnetworkcommunication  connection.h  #import "viewcontroller.h"  @interface connection : viewcontroller  -(void)initnetworkcommunication; @end viewcontroller.h  #import "viewcontroller.h" #import "connection.h"  @interface viewcontroller ()  @end  @implementation viewcontroller  - (void)viewdidload {     [super viewdidload]; }  - (void)didreceivememorywarning {     [super didreceivememorywarning];     // dispose of resources can recreated. } - (void)callmethod {     connection *detailvc = [[connection alloc] init];     [detailvc initnetworkcommunication]; } - (ibaction)connectionbutton:(id)sender {     [self callmethod];  }  @end 

and signal sigabrt show when [self callmethod] called.

to call 1 instance method class, need initialize class , them call. calling method must inside @interface brackets. don't understand why did call "[self initnetworkcommunication]", needn't category or else.

detailviewcontroller.h

@interface detailviewcontroller : uiviewcontroller  -(void)initnetworkcommunication; @end 

detailviewcontroller.m

@implementation detailviewcontroller -(void)initnetworkcommunication {      // } @end 

masterviewcontroller.h

@implementation masterviewcontroller - (void)callmethod {     detailviewcontroller *detailvc = [[detailviewcontroller alloc] init];     [detailvc initnetworkcommunication]; } @end 

update

in .h file making interface category, in .m file making class extension , implementation of class, still doesn't makes interface class.