This is kind of confusing but I will do my best to explain. I have a view controller with a container view. In the container view is a table view. I want to update the tableview from the main view controller. For example, the table view will contain a list of names. As the user types in a name into a text field, the table view will update to find names that match what the user inputed.
The main question is:
How can I update the table view from the main view controller?
Note: I can't use prepare for segue because the data will be changing.
I figured it out...
I can access the view through childviewcontrollers. Here's the code I used:
let childView = self.childViewControllers.last as! ViewController
childView.List = self.nameList
childView.tableView.reloadData()
This is actually a beginner question and I would be happy to help. You need to find a place to store your data and then you can access it based on your need. That's what we normally call model.
You can take advantage of one of the design patter: shared instance. It will be existing during the application life cycle. See the following example.
You can have a model class like this:
// .h
#interface DataManager : NSObject
+ (instancetype)sharedManager;
#property (strong, nonatomic, readonly) NSMutableArray *data;
#end
// .m
#interface DataManager : NSObject
#property (strong, nonatomic, readwrite) NSMutableArray *data;
#end
#implementation DataManager
+ (instancetype) sharedManager {
static DataManager *sharedInstance = nil;
static dispatch_once_t dispatchOnce;
dispatch_once(&dispatchOnce, ^{
sharedInstance = [[self alloc] init];
sharedInstance.data = [[NSMutableArray alloc] initWithCapacity:5];
});
return sharedInstance;
}
#end
Using this, you can access your data via your main view controller or your presenting view controller.
Related
I have 2 Interface Controllers in my WatchKit. The first one is called InterfaceController while the other is called DetailsForWatch. IC has a tableView on it. It parses data from a Parse class, and displays data from each entry in the class as a row. This works fine.
What I am trying to do is pass the PFObject for the selected row to a PFObject in DetailsForWatch. My setup for DFW is:
.h
#interface DetailsForWatch : WKInterfaceController {
}
#property (nonatomic, retain) IBOutlet WKInterfaceLabel *detailsLabel;
#property (nonatomic, retain) PFObject *finalObject;
#end
.m
- (void)awakeWithContext:(id)context {
[super awakeWithContext:context];
NSString *details = self.finalObject [#"Request"];
[self.detailsLabel setText:details];
NSLog(#"%#", self.finalObject);
// Configure interface objects here.
}
In IC, for .h I have:
#class DetailsForWatch;
#interface InterfaceController : WKInterfaceController {
DetailsForWatch *_theDetails;
}
#property (retain) DetailsForWatch *theDetails;
#end
In the .m I have:
#synthesize theDetails = _theDetails;
for didSelectRowAtIndex, I have:
_theObject = _theObjective[rowIndex];
self.theDetails = [[DetailsForWatch alloc] init];
_theDetails.finalObject = _theObject;
I set up the DFW as a Push selection from the Group on IC. When I select a row in the IC, it pushes a blank screen, and the NSLog shows that the PFObject named finalObject is (null). What am I doing wrong that it is not passing on PFObject properly?
There are a couple of ways to pass data between the two interface controllers. The way I have been doing it is like this:
create a segue (give it an identifier if necessary) between the two controllers in my storyboard.
In interface controller 1 implement
- (id)contextForSegueWithIdentifier:(NSString *)segueIdentifier
it will be called when the segue is triggered via button press or whatever.
This can return any object such as a dictionary of the data (in your case 'theDetails')
In interface controller 2 implement
- (void)awakeWithContext:(id)context
the context object here will be the one you passed through in controller 1
So I have 2 different table views that use the same array (the array is originally created in the Role table view, the below one). How can I connect those two?
(Usually I use prepareForSegue to pass the data but since there is no segue, I'm not sure how can I do this)
EDIT 1: Add the location of the array.
What is a Model and why you need it
In most of the cases it's useless to pass data around if you don't have a Data Model. You can store your data using a technique called Data Persistence.
An example of a pattern you could use is MVC.
MVC or model-view controlelr is an software pattern widely using when making iOS Apps. In this architectural pattern your Controllers are a bridge between your View and your Model.
In this specific scenario both UITableViewControllers would use the same Model but they would display this data differently.
Persisting your Model
There are several ways to do that, the way I like the most is a little framework called CoreData, you can see this question for some reference on that.
You can also refer to this question to see the use of Singletons. But keep in mind that singletons alone do not persist the data. You'll have to add some sort of mechanism if you want the data to remain there between app sessions.
Persisting user preferences
The simplest way to store small chunks of data is using NSUserDefaults (but it's only meant to store defaults):
Let's assume you have an array
NSArray* testArray = #[#"first", #"second", #"third"];
You can set it to a key by using
[[NSUserDefaults standardUserDefaults] setObject:testArray forKey:#"myArray"];
You can sync NSUserDefaults using
[[NSUserDefaults standardUserDefaults] synchronize];
Then, anywhere in your app you can read it doing
[[NSUserDefaults standardUserDefaults] objectForKey:#"myArray"]
Passing data through the app
On the other hand you have to pass your data around somehow. To do so you can use formal protocols, specifically delegates.
As per the Apple documentation:
In a delegate-based model, the view controller defines a protocol for
its delegate to implement. The protocol defines methods that are
called by the view controller in response to specific actions, such as
taps in a Done button. The delegate is then responsible for
implementing these methods. For example, when a presented view
controller finishes its task, it sends a message to the presenting
view controller and that controller dismisses it.
Using delegation to manage interactions with other app objects has key
advantages over other techniques:
The delegate object has the opportunity to validate or incorporate
changes from the view controller.
The use of a delegate promotes
better encapsulation because the view controller does not have to know
anything about the class of the delegate. This enables you to reuse
that view controller in other parts of your app.
For more information on passing data through view controllers (the main point of this question) take a look at this SO answer.
You should never use data persistence just to pass data through the app. Neither user defaults nor core data.
Also using singletons is not good choice. All will mess up your memory.
Instead use call backs — either as delegates or blocks.
Or use unwind segues.
I explain delegates and unwind segues here: Passing row selection between view controllers
this example passes index paths, as it is appropriate in that situation, but the passed object might be of any type or size, as only pointers are passes.
if you use the NSUserDefaults on the other side, data is copied and written to the disk — there for data is copied and slowly processed — without any use.
I created a sample app how to pass data from one view controller to another view controller in another tab bar branch.
click to enlarge
TabBarController
We need to intercept the section of view controllers to set up some callback mechanism. In this case I am using blocks, but delegate would work as-well.
UITabController has a purely optional delegate. I create a subclass of UITabBarController to serv as it's own delegate, but actually a separate delegate should work in the same way.
#import "GameTabBarController.h"
#import "RoleViewController.h"
#interface GameTabBarController () <UITabBarControllerDelegate>
#end
#implementation GameTabBarController
-(void)viewDidLoad
{
[super viewDidLoad];
self.delegate = self;
}
-(BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController
{
if ([viewController isKindOfClass:[UINavigationController class]]) {
UINavigationController *navController = (UINavigationController *)viewController;
if ([navController.topViewController isKindOfClass:[RoleViewController class]]) {
RoleViewController *rvc = (RoleViewController *)[navController topViewController];
[rvc setSelectedRole:^(Role *role) {
UIViewController *viewController = self.viewControllers[0];
[viewController setValue:role forKey:#"role"];
[self setSelectedIndex:0];
}];
}
}
return YES;
}
#end
I set the initial tab bar controller to this sub class
Role, RoleDatasource and RoleViewController
The RoleViewController displays a list of Roles, but the datasource and delegate for it's table view are a separate class that I add to the role view controller scene in the storyboard, where i also were it up.
Role
#interface Role : NSObject
#property (nonatomic,copy, readonly) NSString *name;
-(instancetype)initWithName:(NSString *)name;
#end
#import "Role.h"
#interface Role ()
#property (nonatomic,copy) NSString *name;
#end
#implementation Role
- (instancetype)initWithName:(NSString *)name
{
self = [super init];
if (self) {
_name = name;
}
return self;
}
#end
RoleDatasource
#import <UIKit/UIKit.h>
#class Role;
#interface RoleDatasource : NSObject <UITableViewDataSource, UITableViewDelegate>
#property (nonatomic, copy) void(^roleSelector)(Role *role);
#end
#import "RoleDatasource.h"
#import "Role.h"
#interface RoleDatasource ()
#property (nonatomic,strong) NSArray *roles;
#end
#implementation RoleDatasource
- (instancetype)init
{
self = [super init];
if (self) {
_roles = #[[[Role alloc] initWithName:#"Magician"], [[Role alloc] initWithName:#"Soldier"], [[Role alloc] initWithName:#"Maid"]];
}
return self;
}
-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.roles.count;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *identifier = #"RoleCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier forIndexPath:indexPath];
cell.textLabel.text = [self.roles[indexPath.row] name];
return cell;
}
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
self.roleSelector(self.roles[indexPath.row]);
}
#end
RoleViewController
#import <UIKit/UIKit.h>
#class Role;
#interface RoleViewController : UIViewController
#property (nonatomic, copy) void(^selectedRole)(Role *role);
#end
#import "RoleViewController.h"
#import "RoleDatasource.h"
#interface RoleViewController ()
#property (weak, nonatomic) IBOutlet UITableView *tableView;
#end
#implementation RoleViewController
- (void)viewDidLoad {
[super viewDidLoad];
RoleDatasource *roleDataSource = (RoleDatasource *)[self.tableView dataSource];
[roleDataSource setRoleSelector:^(Role *role) {
self.selectedRole(role);
}];
}
#end
PlayViewController
As soon as a role is selected on the role view controller we want to tell our tab bar controller to switch to the game view controller and show the selected role there, see the code for the tab bar controller.
The GameViewController is just a simple view controller subclass that has a property to hold a role and if a role is set, it will displays it name.
#import <UIKit/UIKit.h>
#class Role;
#interface PlayViewController : UIViewController
#property (nonatomic, strong) Role *role;
#end
#import "PlayViewController.h"
#import "Role.h"
#interface PlayViewController ()
#property (weak, nonatomic) IBOutlet UILabel *roleNameLabel;
#end
#implementation PlayViewController
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
self.roleNameLabel.text = (self.role) ? self.role.name : self.roleNameLabel.text;
}
#end
You'll find an example on github.
I think that I should put the array in the Tab bar Controller and connect it to the Role Table view (in order to maintain the behaviour like it is before) and connect it to my new Table view to do what I want to do.
The only problem I can think of is that since my program is small, adding this will not be a big problem. But if I have more vc, it's going to be so much pain.
I have an NSMutableArray declared as property in .h and initialized in viewDidLoad in my SPOCVC .m (UIViewController)...
#property (strong, nonatomic) NSMutableArray* SPOCTrackList;
in viewDidLoad
if ([self SPOCTrackList] == nil) {
self.SPOCTrackList = [[NSMutableArray alloc]init];
NSLog(#"SPOTTrackList INITIALIZED");
}
In a separate VC, I'm trying to pass/addObject to SPOCTracklist...
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
SCTrack* selectedTrack = self.trackList[indexPath.row];
[[[SPOCVC sharedInstance]SPOCTrackList]addObject:selectedTrack];
NSLog(#"%lu", (unsigned long)[[[SPOCVC sharedInstance]SPOCTrackList]count]);
So my NSMutableArray is initialized and I can add dummy objects, but why can't I pass it from another VC using singleton or anything, such as...
SPOCVC* spocVC = self.tabBarController.viewControllers[2];
[spocVC.SPOCTrackList addObject:selectedTrack];
Thanks for pointing me in the right direction.
View controllers are only intended to be around while they are on screen. They are not a place to store data. Generally when one view controller talks directly to another view controller that it didn't create, you're doing something wrong.
Move SPOCTrackList to your model and have both view controllers talk to it rather than to each other.
There should never be a "sharedInstance" on a view controller. That's a sure sign that you're abusing the view controller as the model.
What's probably happening in your particular case is that viewDidLoad is running on a completely different SPOCVC than your sharedInstance.
why not use appdelegate to handle this
appdelegate.h
//add property to hold the reference
#property (nonatomic, copy) NSMutableArray *referenceArray;
//share the app delegate
+(AppDelegate *)sharedAppDelegate;
#end
in appdelegate.m
//synthesize the property
#synthesize referenceArray;
//return the actual delegate
+(AppDelegate *)sharedAppDelegate {return (AppDelegate *)[UIApplication sharedApplication].delegate;}
in viewdidload method
//add the delegate
import "appdelegate.h"
//init the array
self.SPOCTrackList = [[NSMutableArray alloc]init];
//Add reference
[AppDelegate sharedAppDelegate].referenceArray = self.SPOCTrackList;
and add anywhere like this
import "appdelegate.h"
[[AppDelegate sharedAppDelegate].referenceArray addobject:object];
This question already has answers here:
Passing data between view controllers
(45 answers)
Closed 9 years ago.
I need to make one instance of an array that can be access by multiple view controllers. It will contain objects that will be displayed in a table view and created by a modular view and then displayed in the table view. I can't figure out how to access it once I make a #property for it in the main view controller or the AppDelegate class.
You should make a singleton and the recommended way to do that in objective-c is to create a class and add a method that looks something like:
+ (YourClass *)sharedYourClass
{
static dispatch_once_t onceToken;
static YourClass *sharedInstance;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
Put the array as a property in your class.
//YourClass.h
#interface YourClass : NSObject
#property(nonatomic, strong)NSArray *yourArray;
+(YourClass *)sharedYourClass;
#end
And in every class you want to use your singleton start by importing YourClass.h and then use it like:
NSArray *arr = [YourClass sharedYourClass].yourArray;
[YourArray sharedYourClass].yourArray = [[NSArray alloc] init];
etc..
What I do is put the data I want shared, in your instance the array, in the AppDelegate. Then I define a protocol that the app delegate conforms to. This lets me access the data anywhere. For example, say I have an array I want everywhere:
First define a protocol:
#protocol ApplicationState<NSObject>
#property(nonatomic, strong) NSArray* data;
#end
Then make your app delegate conform to it:
#interface AppDelegate : UIResponder <UIApplicationDelegate, ApplicationState>
#property (strong, nonatomic) UIWindow *window;
#property(nonatomic, strong) NSArray* data;
#end
Then reading and writing this shared object is simple:
id<ApplicationState> appState = (id<ApplicationState>) [UIApplication sharedApplication].delegate;
appState.data = [[NSArray alloc] init];
I am going to assume you can make the class of the array inherit from NSObject, and then pass it to the View Controller from there...
You have 2 ways to do this:
1.- Instantiate 1 arra on the main class and pass the reference to each viewcontroller what you need.
2.- Make a singleton class to hold the array an use this in your project.
First create a class like this
//GlobalDataClass.h
#interface GlobalDataClass : NSObject
#property(nonatomic,retain)NSArray *myArray;
+(GlobalDataClass*)getInstance;
#end
#import "GlobalDataClass.h"
//GlobalDataClass.m
#implementation GlobalDataClass
#synthesize myArray;
static GlobalDataClass *instance =nil;
+(GlobalDataClass *)getInstance
{
#synchronized(self)
{
if(instance==nil)
{
instance = [GlobalDataClass new];
}
}
return instance;
}
#end
Then you can use it in your viewControllers like this:
-(void)viewDidLoad{
[super viewDidLoad];
self.dataObj = [GlobalDataClass getInstance];
NSLog(#"%#",self.dataObj.myArray);
}
Hope it helps!
I'm pretty new to programming. I am creating a very simple iOS Quiz app just for practice. Here is what I have gotten done thus far:
I created the Xcode project using the "Single View" template. Thus, I already have the appDelegate files, the View Controller and a View (XIB file).
My view only has four controllers: 2 UILabels and 2 UIButtons. Each button is paired up with a label. I have all the connections for these 4 controllers setup. When the user taps the button labelled "Get a State" it needs to populate it's label with the name of a state I have in an NSMutableArray called stateArray. When the user taps on the button labelled "Get Capital" is needs to populate it's label with the state's capital in it's label.
I created an Objective-C class that inherits from NSObject to hold my data model called dataModel. In the dataModel.m file I have created and populated the two arrays.
In the view controller .m file I imported the dataModel.h file.
The only problem I am having is getting the view controller to retrieve data from the dataModel file. I have read that I should probably be using Delegation, but I am just looking to know how to do it more simply...I ready something about the view controller and the data model file should have references to each other? If so, what would the coding look like?
Here is my coding thus far:
#import <UIKit/UIKit.h>
#interface onMyOwnViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *stateField;
#property (weak, nonatomic) IBOutlet UILabel *answerField;
- (IBAction)answerButton:(id)sender;
- (IBAction)stateButton:(id)sender;
#end
#import "onMyOwnViewController.h"
#import "dataModel.h"
#implementation onMyOwnViewController
- (IBAction)stateButton:(id)sender
{
NSString *myState = [stateArray objectAtIndex:0]; //this line produces an error.
[_stateField setText:myState];
[_answerField setText:#"hi"];
}
- (IBAction)answerButton:(id)sender
{
}
#end
Below is my dataModel coding:
#import <Foundation/Foundation.h>
#interface dataModel : NSObject
#property(nonatomic, strong) NSMutableArray *answerArray;
#property(nonatomic, strong) NSMutableArray *stateArray;
#end
#import "dataModel.h"
#import "onMyOwnViewController.h"
#implementation dataModel
- (id)init
{
self = [super init];
if(self){
_answerArray = [[NSMutableArray alloc]initWithObjects:#"Michigan", #"Illinios", nil];
_stateArray = [[NSMutableArray alloc]initWithObjects:#"Lansing", #"Springfield",
nil];
}
return self;
}
#end
When I run the app, everything works except retrieving data from the data model. When you replay, please reply with coding.
You need to create an instance of your dataModel in onMyOwnViewController.
#implementation onMyOwnViewController {
dataModel *data;
}
-(void)viewDidLoad {
data = [[dataModel alloc] init];
}
Then in your method call
- (IBAction)stateButton:(id)sender
{
NSString *myState = data.stateArray[0];
...
}