I have a storyboard in which I have specified a parent view controller and two container views (made up of two UITableViewControllers). In my parent view controller I have buttons that are used to filter the content of the two tables.
My problem is figuring out how to send messages to the container views to perform these filters. I imagine we use delegates but is there a best practice way of implementing these delegates?
Subject to some caveats, you could define properties for each of the two contained tables, connect the outlets in your .xib, and message them directly in your button handlers.
For example:
#interface ParentViewController : UIViewController
#property (nonatomic) IBOutlet Table1Class *table1;
#property (nonatomic) IBOutlet Table2Class *table2;
#end
#implementation ParentViewController
...
- (IBAction)table1FilterButton:(UIButton *)sender
{
[self.table1 filterBy:...];
}
- (IBAction)table2FilterButton:(UIButton *)sender
{
[self.table2 filterBySomethingElse:...];
}
#end
Now, the caveats - you probably won't want to do this if you anticipate that the number of contained view controllers is likely to grow significantly, as it will be unwieldy to have table1, table2, table3, ..., tableN. You'll probably also want to find a way to extract a common interface (in the form of a protocol) from the two contained view controllers, in order to write less divergent code for handling the filtering of each table.
Maybe something like this, instead:
#protocol ContainedTableProtocol
#property (nonatomic) NSPredicate *contentFilterPredicate;
#property (nonatomic) NSComparator sortComparator;
#end
#interface ParentViewController : UIViewController
#property (nonatomic) IBOutlet UITableViewController<ContainedTableProtocol> *table1;
#property (nonatomic) IBOutlet UITableViewController<ContainedTableProtocol> *table2;
#end
#implementation ParentViewController
- (IBAction)filterTable1ButtonAction:(UIButton *)sender
{
[self filterTable:self.table1];
}
- (IBAction)filterTable2ButtonAction:(UIButton *)sender
{
[self filterTable:self.table2];
}
- (void)filterTable:(UITableViewController<ContainedTableProtocol> *)table
{
// Create predicate and comparator as needed...
NSPredicate *predicate = ... ;
NSComparator comparator = ... ;
table.contentFilterPredicate = predicate;
table.sortComparator = comparator;
}
#end
This uses a common interface to apply the filtering operations to each table view controller, and then codes to that interface rather than an API specific to a particular Table1Class or Table2Class.
You can see the answer at How do I create delegates in Objective-C?.
The simpler way is declare the delegate in the Childs and implement in the parent (ie: The childs send data to the parent).
Related
I have a sequencer with each track that has buttons as an outlet collection. The code all works fine in it's own view controller however I want to transfer all the methods to a singleton so that I can control the playback from other views.
for instance I have
#property (strong, nonatomic) IBOutletCollection(UIButton) NSArray *trackOneOutletCollection;
However I have methods which act on the alpha and tags of each button; the methods contain these vales which I don't know how to access from the singleton. I thought the singleton was where I store all the data and then call it from the class file view controller?
You can use Inheritance concept to achieve this functionality.you need to create one ParentViewController that hold IBOutletCollection property. and rest of all View Controller is child of ParentViewController. then you can access IBOutletCollection in other view ontroller. like this way.
ParentViewController:-
#interface ParentViewController : UIViewController
#property (strong, nonatomic) IBOutletCollection(UIButton) NSArray *trackOneOutletCollection;
#end
ChildViewController;-
#interface YourViewController : ParentViewController
#end
.m file
#implementation YourViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"trackOneOutletCollection = %#"self.trackOneOutletCollection);
}
#end
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 am trying to do the following, and not able to find a straightforward answer.. It is related to this :Passing uitextfield from one view to another. But not exactly.
I have a Firstview.m, from which I push to a Secondview.m. The Secondview.m has a UITextView. I allow the user to edit the UITextView on Secondview.m. Now I want to store this text value in a variable in Firstview.m. One way to to do this is as follows
in Firstview.h
#property (nonatomic) Secondview *secondView;
That is keep a secondView variable in Firstview itself. But this doesn't seem efficient. Ideally I should only have 1 NSString text field in FirstView. What is the right way to do this ? Thanks
You can achieve this by using Delegation in Objective-C.
In your SecondView.h add following right after Header Inclusion
#protocol YourDelegateName <NSObject>
-(void)setText:(NSString *)strData;
#end
Also add delegate property to your header for accessing them in calling class, like below (This goes with other properties declaration in SecondView.h file):
#property (nonatomic, weak) id<YourDelegateName> delegate;
Now, Comes the calling the delegate part. Say, you want to save the text value of UITextView of SeconView in strTextViewData of FirstView class, when the following event occurs:
- (IBAction)save:(id)sender
{
[self.delegate setText:self.txtView.text]; // Assuming txtView is name for UITextView object
}
Now, In FirstView.h add YourDelegateName in delegate list like below:
#interface FisrtView : ViewController <YourDelegateName>
#property (nonatomic, reatin) NSString *strTextViewData;
#end
And then in FisrtView.m file when you create instance of SecondView class, set delegate to self like below:
SecondView *obj = [[SecondView alloc] initWithNibName:#"SeconView" bundle:nil];
obj.delegate = self; // THIS IS THE IMPORTANT PART. DON'T MISS THIS.
Now, Implement the delegate method:
-(void)setText:(NSString *)strData
{
self.strTextViewData = strData;
}
Applying this to your code will do what you want. Also, Delegation is one of the most important feature of Objective-C language, which - by doing this - you will get to learn.
Let me know, if you face any issue with this implementation.
When the views are simple, their IBActions and IBoutlets are in viewcontroller, viewcontrollers assigns respective models to be loaded and viewcontroller get notified when models are prepared.
As My project contains lot of custom views for each viewcontroller, I want to implement actions in custom view itself and set data from controller (ViewController).
I should be able to use the same controllers and models for both iPhone and iPad where only UI changes.
I am concerned about how to pass data from view to viewcontroller and displaying data back on view when model changes?
Can anyone please suggest me to pass data between views <---> viewcontroller (controller) <---> model?
To do this I use Delegate design-pattern. It looks like this :
MyView.h
#protocol MyViewDelegate <NSObject>
- (void)customViewDidSomething;
#end
#interface MyView : UIView
#property (nonatomic, assign) id<MyViewDelegate> delegate
#end
MyView.m
- (void)userDidSomething {
[_delegate customViewDidSomething];
}
MyViewController.h
#import "MyView.h"
// ViewController has to implement the protocol
#interface MyViewController <MyViewDelegate>
#property (nonatomic, retain) IBOutlet MyView myView;
MyViewController.m
- (void)viewDidLoad { // Set the delegate somewhere
_myView.delegate = self
}
- (void)customViewDidSomething {
// Ok VC is aware that something happened
// Do something (tell subview to do something ?)
}
Instead of using different custom views, try using a UIViewController and then use the viewcontroller's view to display your UI. Also, this will also ensure that you will be able to communicate between the views and controller efficiently without confusion.
I have a UIViewsubclass. I am not able to create an instance of another View Controller in this UIView class, so that i can access the variables set in my UIView subclass in this View Controller? Can anyone guide me on this
#import <UIKit/UIKit.h>
#import "DirectoryFormViewController.h"
#class NIDropDown;
#protocol NIDropDownDelegate
- (void) niDropDownDelegateMethod: (NIDropDown *) sender;
#end
#interface NIDropDown : UIView <UITableViewDelegate, UITableViewDataSource>
{
NSString *animationDirection;
UIImageView *imgView;
DirectoryFormViewController *dict; // i am not able to create this
}
#property (nonatomic, retain) id <NIDropDownDelegate> delegate;
#property (nonatomic, retain) NSString *animationDirection;
-(void)hideDropDown:(UIButton *)b;
- (id)showDropDown:(UIButton *)b:(CGFloat *)height:(NSArray *)arr:(NSArray *)imgArr: (NSString *)direction;
#property(nonatomic)int countryID;
#end
My DirectoyFormViewController:
#import <UIKit/UIKit.h>
#import "NIDropDown.h"
#interface DirectoryFormViewController : UIViewController<DropDownListDelegate,CLLocationManagerDelegate,UISearchBarDelegate,UITextFieldDelegate,NIDropDownDelegate>
#property(nonatomic)NSMutableDictionary *countryName;
#property(nonatomic,copy)NSMutableDictionary *sortName;
#property(nonatomic,copy)NSMutableDictionary *resultName;
#end
I want to set countryName,sortName and resultName in my NIDropDown
Thanks
Here's the short answer: you should never, ever, not for any reason create an instance of a view controller inside of a UIView. So the fact that you have not been successful so far is a good thing.
The Apple way of development on iOS is to use the Model, View, Controller design pattern. In MVC, the controller controls the models and the views and mediates communication between the two... not the other way around.
My suggestion is that you read the link and fully understand it before moving forward with development. With an understanding of the topics covered you'll never do things like have a UIView that's a table view delegate / datasource (because by doing that, your view is aware of the model, and that breaks MVC), and you'll hopefully never try to do things like create a UIViewController in a UIView.