ios - Passing Data between View Controllers -

ios - Passing Data between View Controllers -

i'm new ios and, objective-c , whole mvc paradigm , i'm stuck following:

i have view acts info entry form , want give user alternative select multiple products. products listed on view uitableview controller , have enabled multiple selections.

my question is, how transfer info 1 view another? holding selections on uitableview in array, how pass previous info entry form view can saved along other info core info on submission of form?

i have surfed around , seen people declare array in app delegate. read singletons don't understand these , read creating info model.

what right way of performing , how go it?

this question seems popular here on stackoverflow thought seek , give improve reply help out people starting in world of ios me.

i hope reply clear plenty people understand , have not missed anything.

passing info forward

passing info forwards view controller view controller. utilize method if wanted pass object/value 1 view controller view controller may pushing on navigation stack.

for illustration have viewcontrollera , viewcontrollerb

to pass bool value viewcontrollera viewcontrollerb following.

in viewcontrollerb.h create property bool

@property(nonatomic) bool *issomethingenabled;

in viewcontrollera need tell viewcontrollerb utilize

#import "viewcontrollerb.h"

then want load view eg. didselectrowatindex or ibaction need set property in viewcontrollerb before force onto nav stack.

viewcontrollerb *viewcontrollerb = [[viewcontrollerb alloc] initwithnib:@"viewcontrollerb" bundle:nil]; viewcontrollerb.issomethingenabled = yes; [self pushviewcontroller:viewcontrollerb animated:yes];

this set issomethingenabled in viewcontrollerb bool value yes.

passing info forwards using segues

if using storyboards using segues , need procedure pass info forward. similar above instead of passing info before force view controller, utilize method called

-(void)prepareforsegue:(uistoryboardsegue *)segue sender:(id)sender

so pass bool viewcontrollera viewcontrollerb following:

in viewcontrollerb.h create property bool

@property(nonatomic) bool *issomethingenabled;

in viewcontrollera need tell viewcontrollerb utilize an

#import "viewcontrollerb.h"

create segue viewcontrollera viewcontrollerb on storyboard , give identifier, in illustration we'll phone call "showdetailsegue"

next need add together method viewcontrollera called when segue performed, because of need observe segue called , something. in our illustration check "showdetailsegue" , if thats performed pass our bool value viewcontrollerb

-(void)prepareforsegue:(uistoryboardsegue *)segue sender:(id)sender{ if([segue.identifier isequaltostring:@"showdetailsegue"]){ viewcontrollerb *controller = (viewcontrollerb *)segue.destinationviewcontroller; controller.issomethingenabled = yes; } }

if have views embedded in navigation controller need alter method above following

-(void)prepareforsegue:(uistoryboardsegue *)segue sender:(id)sender{ if([segue.identifier isequaltostring:@"showdetailsegue"]){ uinavigationcontroller *navcontroller = (uinavigationcontroller *)segue.destinationviewcontroller; viewcontrollerb *controller = (viewcontrollerb *)navcontroller.topviewcontroller; controller.issomethingenabled = yes; } }

this set issomethingenabled in viewcontrollerb bool value yes.

passing info back

to pass info viewcontrollerb viewcontrollera need utilize protocols , delegates or blocks, latter can used loosely coupled mechanism callbacks.

to create viewcontrollera delegate of viewcontrollerb. allows viewcontrollerb send message viewcontrollera enabling send info back.

for viewcontrollera delegate of viewcontrollerb must conform viewcontrollerb's protocol have specify. tells viewcontrollera methods must implement.

in viewcontrollerb.h, below #import, above @interface specify protocol.

@class viewcontrollerb; @protocol viewcontrollerbdelegate <nsobject> - (void)additemviewcontroller:(viewcontrollerb *)controller didfinishenteringitem:(nsstring *)item; @end

next still in viewcontrollerb.h need setup delegate property , synthesize in viewcontrollerb.m

@property (nonatomic, weak) id <viewcontrollerbdelegate> delegate;

in viewcontrollerb phone call message on delegate when pop view controller.

nsstring *itemtopassback = @"pass value viewcontrollera"; [self.delegate additemviewcontroller:self didfinishenteringitem:itemtopassback];

that's viewcontrollerb. in viewcontrollera.h, tell viewcontrollera import viewcontrollerb , conform protocol.

#import "viewcontrollerb.h" @interface viewcontrollera : uiviewcontroller <viewcontrollerbdelegate>

in viewcontrollera.m implement next method our protocol

- (void)additemviewcontroller:(viewcontrollerb *)controller didfinishenteringitem:(nsstring *)item { nslog(@"this returned viewcontrollerb %@",item); }

the lastly thing need tell viewcontrollerb viewcontrollera delegate before force viewcontrollerb on nav stack.

viewcontrollerb *viewcontrollerb = [[viewcontrollerb alloc] initwithnib:@"viewcontrollerb" bundle:nil]; viewcontrollerb.delegate = self [[self navigationcontroller] pushviewcontroller:viewcontrollerb animated:yes]; references using delegation communicate other view controllers in view controller programming guide delegate pattern

ios objective-c oop uitableview uiviewcontroller