I am trying to call a method thats in my ViewController from a NSObject Class thats doing some parsing.
I initally call a connection class I have made wich downloads some data from my server, I then pass this data over to a parser class I have made, now what I am trying to do is pass this data back to the viewcontroller and reload the tableview thats in this view (thats on a navigation stack)
anyway this is causing some errors and I think it might be the way I am trying to call this method thats doing it. here is how I call it.
MyViewController *myViewController = [[MyViewController alloc] init];
[myViewController initFilterArray:filteredArray];
Now I think this is causing an issue because I am allocating a new viewcontroller object? is that right.. not to sure of the terminoligy.. but yea..
the result of which is that reloaddata is only calling
numberOfSectionsInTableView
tableView:numberOfRowsInSection
then thats it.
any help would be appreciated.
UPDATE:
so I am trying to set up a protocol/delegate to see if that fixes my problem.
so in my class.h this is what I am doing
#protocol PassParsedData <NSObject>
#required
- (void) sendMyArray:(NSArray *)modelArray;
#end
//..
id <PassParsedData> delegate;
//..
#property (strong) id delegate;
then in class.m
//..method
[[self delegate]sendMyArray:filteredArray];
//..
so thats my class, then over in my view controller where I want to call this sendMyArray I do this
viewcontroller.h
#import "class.h" //delegates & protocols
//..
interface VehicleSearchViewController : UITableViewController <PassParsedData> {
//..
then i call it like this
viewcontroller.m
//..
- (void)sendArray:(NSArray *)array
{
ICMfgFilterArray = array;
[self.tableView reloadData];
}
One way of doing this would be the recommended approach of delegates and protocols.
Your NSObject declares a protocol. The ViewController actually implements the protocol and sets itself as the delegate. Then the NSObject calls the method (not knowing who implements it). It is a loosely-coupled way to communicate between objects.
I actually recently wrote a blog post on a basic introduction to protocols and delegates if you're interested...
UPDATE
Based on your update above in question.
Don't forget to set your ViewController to be the delegate.
- (void)viewDidLoad {
// State that you will take care of messages from graphView (provided you have the protocol implementation!)
self.yourClass.delegate = self;
}
And the method in your ViewController should match the protocol signature. So in ViewController.m
- (void) sendMyArray:(NSArray *)modelArray {
ICMfgFilterArray = array;
[self.tableView reloadData];
}
Related
I am working on a splitView application for my iPad. I have implemented a UIButton called as Upload. On clicking on it, a UITableView appears inside a UIPoverController. On clicking on any of the contents, I want to display some respective site in my UIwebView in UIDetailView. For this I have implemented a delegate method protocol. I have used the following lines of code in UploadTableViewController.h file::
#protocol UploadTableViewDelegate <NSObject>
#required
- (void)selected:(NSString *)his;
#end
#interface UploadSpaceTableViewController : UITableViewController{
id<UploadSpaceTableViewDelegate> delegate;
}
#property (retain) id delegate;
#end
In the corresponding .m file I have used the following lines of code ::
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
if (delegate != nil) {
NSString *hisSelected = [keys objectAtIndex:indexPath.row];
NSLog(#"%# lolwa", hisSelected);
[delegate selected:hisSelected];
}
}
in the .m file of class where I have implemented the function Selected, the code is ::
- (void)selected:(NSString *)Key {
NSLog(#"hello");
[self.UploadSpaceTableViewPopover dismissPopoverAnimated:YES];
}
-(IBAction)uploadpressed:(id)sender{
Upload.delegate = self;
self.Upload = [[UploadSpaceTableViewController alloc]
initWithStyle:UITableViewStylePlain];
self.UploadTableViewPopover = [[UIPopoverController alloc]
initWithContentViewController:UploadSpace];
[self.UploadTableViewPopover presentPopoverFromBarButtonItem:sender
permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
}
However, I am unable to get hello (written in the function Selected) NSLogged in gdb. This is the first time that I am using this delegate method protocol. I am unable to sort this out. Can someone help me out ? Thanks and regards.
[delegate keySelected:hisKeySelected]; is your first problem. You don't declare a delegate method named -keySelected:, you declare a delegate method named -Selected:.
Your second problem is the fact that you are most definitely not the delegate of your table view. In order for a delegate method like -didSelectRowAtIndexPath: to be called, you must be the table's delegate.
PS, don't begin instances, or method names, with an uppercase letter. In ObjC, uppercase letters indicate a class.
EDIT: this is what your UploadSpaceTableViewController header should look like:
#protocol UploadTableViewDelegate <NSObject>
#required
- (void)selected:(NSString *)his;
#end
#interface UploadSpaceTableViewController : UITableViewController<UITableViewDataSource, UITableViewDelegate>
#property (nonatomic, assign) id <UploadSpaceTableViewDelegate>delegate; //delegates are weak!!!
#end
And the .m, I will skip a lot of the unnecessary stuff:
-(void)viewDidLoad {
[self.tableView setDelegate:self];
[self.tableView setDataSource:self];
}
//other code
Furthermore, your delegate is declared retain, which is an absolutel No-No in ObjC. Declare is weak if using ARC, or assign if not.
You are also producing a nil delegate in in your -uploadPressed: method by setting it before you explicitly own or initialize the object. Here's how it should look:
self.Upload = [[UploadSpaceTableViewController alloc]initWithStyle:UITableViewStylePlain];
Upload.delegate = self;
Delegation works like this
declare a protocol - you have done this
declare a delegate property - you have done this
In the class which you want to be the delegate say it conforms to the protocoll
#interface MyClass : MySuperClass <UploadTableViewDelegate>
set the delegate property so the delegate class can get the delegate messages
uploadSpaceTVC.delegate = self;
call the delegate methods in your non delegate class (UploadSpaceTableViewController)
[self.delegate selected:#"test"];
As a new iOS developer, I have finally stumbled across delegates. I'm trying to follow a tutorial: http://gabriel-tips.blogspot.com/2011/05/input-accessory-view-how-to-add-extra.html, But I'm having difficulty understanding where I am supposed to put the actual delegate methods.
Secondly, would anyone mind providing a dumbed down explanation of how a delegate method is invoked?
Thanks!
A delegate is simply a class that agrees to do work for another class. The delegate methods are invoked by the delegating class. The delegate must therefore, provide an implementation of the appropriate method. Let's make a simple view controller with a table view.
// MyViewController.h
#interface MyViewController : UIViewController <UITableViewDelegate>
#property (nonatomic, retain) UITableView *myTableView;
#end
Here in the MyViewController.h file I have declared my view controller to be a delegate of type UITableViewDelegate (it really means it implements the UITableViewDelegate protocol. More on this later). I have thus agreed to respond to requests to my view controller. The requests will come from the table view called myTableView. However, simply stating that I adhere to UITableViewDelegate does not make my view controller a delegate of anything. I must specify that directly:
// MyViewController.m
#import "MyViewController.h"
#implementation MyViewController
- (void)loadView
{
myTableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
myTableView.delegate = self;
self.view = myTableView;
}
#end
Here I specifically set MyViewController to be the delegate of myTableView. Now whenever the table view wants to ask its delegate to do something, it will send that message to my view controller. Thus, MyViewController MUST provide implementations of the appropriate delegate methods:
// MyViewController.m
#import "MyViewController.h"
#implementation MyViewController
- (void)loadView
{
myTableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
myTableView.delegate = self;
self.view = myTableView;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"Selected section:%i row:%i", indexPath.section, indexPath.row);
}
#end
Here I have provided an implementation for the delegate method tableView:didSelectRowAtIndexPath: which will be called by myTableView when it is appropriate (the user selects a row).
Here you can find all the delegate methods defined in UITableViewDelegate. Some are required and others are optional:
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UITableViewDelegate_Protocol/Reference/Reference.html
In order to be a delegate of a class you should know which methods you are required to provide implementations for.
If you wanted to create your own delegate definitions, you would create a new protocol. You do not retain your delegates (see the property declaration), as this creates a retain cycle:
// MyViewController.h
#class MyViewController;
#protocol MyViewControllerDelegate
- (void)viewController:(MyViewController *)viewController didChangeSelection:(NSIndexPath *)newIndexPath;
#end
#interface MyViewController : UIViewController <UITableViewDelegate>
#property (nonatomic, retain) UITableView *myTableView;
#property (nonatomic, assign) id<MyViewControllerDelegate> delegate;
#end
Here we have created a new protocol. Any class that wants to be respond to the viewController:didChangeSelection: message could now do so. Just like with the table view above it would set the delegate to itself and then implement the method. Now that you have a delegate, you can invoke the method at an appropriate time.
// MyViewController.m
#import "MyViewController.h"
#implementation MyViewController
- (void)loadView
{
myTableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
myTableView.delegate = self;
self.view = myTableView;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"Selected section:%i row:%i", indexPath.section, indexPath.row);
indexPath = [NSIndexPath indexPathForRow:1 inSection:0];
[self.delegate viewController:self didChangeSelection:indexPath];
}
#end
Now the delegate can receive the message and do what it wants knowing that my view controller changed the selection.
A delegate pattern is a convenient way to allow for the communication between independent controller that allows for loose coupling. So let's say you have a pattern like this:
A
/ \
B C
Where A instantiates B and C. Communicating between A to B and A to C are easy but how would you communicate between B and C? B to A? C to A? There are a couple different ways you could do so such as Key-Value Observing or Block Callbacks. Delegation, though, are still most frequently used although Blocks are coming on strong.
In this example, object A instantiates object B to create an object and fill it with info. How would object B pass the new object back to A as you want to keep things loose? Well, with these 9 easy steps, you can do it too! It may not make sense but we'll start with ClassB…
// ClassB.h
#protocol ClassBDelegate; //(1)
#interface ClassB : NSObject
#property (nonatomic, weak) id<ClassBDelegate>bDelegate; //(2)
-(void)makeNewObjectAndSendBack;
#end
#protocol ClassBDelegate : NSObject //(3)
-(void) classB:(Class B *)theClassB finishedWithObject:(id)finishedObject; //(4)
#end
ClassB.m
#implementation
#synthesize bDelegate = _bDelegate; //(5)
-(void)makeNewObjectAndSendBack {
//something something something
[self.bDelegate classB:self finishedWithObject:newObject]; //(6)
}
#end
define the protocol that will be established later
set an instance of an object that will conform to that protocol
set up the protocol
set up the method call that you'll use to send the finishedObject back to A.
synthesize the delegate
after you do what you need to do, you send it back using the method
you defined in 4
// ClassA.h
#interface ClassA : NSObject <ClassBDelegate> //(7)
#property (nonatomic, strong) ClassB theClassB;
-(void)yourMethodToDoSomething;
#end
ClassA.m
#implementation
#synthesize theClassB = _theClassB;
-(void)randomMethod {
self.theClassB = [ClassB new];
self.theClassB.bDelegate = self; //(8)
[self.theClassB makeNewObjectAndSendBack];
}
-(void) classB:(Class B *)theClassB finishedWithObject:(id)finishedObject { //(9)
[self doSomethingWithFinishedObject:finishedObject]; //ta-da!
}
#end
7.Conform to the ClassBDelegate protocol. This basically says that you
will implement the methods defined in the protocol definition.
8.Set the classB object's delegate object as self! This is crucial and
often skipped.
9.Implement the delegate method for when you get the new object back.
So the process, in short is: A instanciate B. A sets B's delegate as self. A tells B to do something. B does something and sends object back via delegate method. A gets it back.
For more information, including what you can do with protocols, check out:
Big Nerd Ranch talk about Protocols
Part 1
Part 2
Part 3
Good luck!
It seems you might be a little confused as to what delegates are and how they are used. Here are two links to Apple documentation you might find useful: A conceptual overview and a more in depth explaination.
I have been working on this problem for close to 4 days now.
I am at the point where I think its not so much a problem with my code, but the structure of my application that is causing the issue.
I am trying to implement protocols and delegates to get an array from one NSObject(class) to a ViewController.
my code is pretty much line by line copied from this tutorial the only differences are in the face I have ARC turned on so have had to replace (nonatomic, retain) to (strong) and have not used dealloc :)
so with that being said its still not passing the data back to the viewcontroller. (highly annoying) I have tried dozens of different combinations of solutions that I have had help with and nothing has worked. This has lead me to believe that maybe there is an error in the structure of my application or the way things have been initialized etc, which I will attempt to explain now.
When my viewcontroller with tableview loads the viewdidload method called the delegate of my parser class, then once the first cell of the tableview has loaded it called my connection class and tells it to download some data from the server.
Inside my connection class I use NSURLConnection delegates from the apple library, in the delegate method connectionDidFinishLoading the data that has been downloaded is passed over to my parser class (however this is where i think its going wrong because i declare the object again.. which i think is where things are going amiss)
this is how I call my parser class from my connection class.
parserClass *myparser = [[EngineResponses alloc] init];
[myparser ReciveResponse:receivedData];
then once the data is in my parser class it gets parsed and then I try to pass the data across to my viewcontroller.. but its never accessing that delegate method that I set up.
Hopefully this is where the problem is because I just dont know where else I am going wrong.
what do you think?
UPDATE: heres my code -
ViewController.h
#import "EngineResponses.h" //delegates & protocols
interface SearchViewController : UITableViewController <PassParsedData> {
//delegates to parser class
EngineResponses *engineResponses;
//..
ViewController.m
#import "EngineResponses.h"
//this is where I set up the delegate/protocol for the parser class
- (void)viewDidLoad
{
[super viewDidLoad];
//..
engineResponses = [[EngineResponses alloc] init];
[engineResponses setMydelegate:self];
//..
}
//this is where i set up and call the connection class
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
//..
if(indexPath.section == 0){
//..
if (indexPath.row == 0){
EngineRequests *engineRequests = [[EngineRequests alloc] init];
[engineRequests initalizePacketVariables:0 startCode:#"myReg" activationCode:#"myAct" methodName:#"GetStuff"];
//..
}
#pragma - Reciver methods
- (void)sendArray:(NSArray *)array
{
ICMfgFilterArray = array;
[self.tableView reloadData];
}
EngineRequests.m
//connection delegates etc..
//then I pass the data from the connection delegates over to the parser class
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
EngineResponses *engineResponses = [[EngineResponses alloc] init];
[engineResponses ReciveResponse:receivedData];
}
EngineResponses.h
#protocol PassParsedData
- (void)sendArray:(NSArray *)array;
#end
//..
id <PassParsedData> mydelegate;
//..
#property (strong) id <PassParsedData> mydelegate;
EngineResponses.m
- (void)parserDidEndDocument:(NSXMLParser *)parser
{
//..
[[self mydelegate]sendArray:filteredArray];
}
1
Allright. I will re-do it based on your updated code. To make it easy I copy your code and do the amendments.
ViewController.h
#import "EngineResponses.h" //delegates & protocols
interface SearchViewController : UITableViewController <PassParsedData> {
//delegates to parser class
EngineResponses *engineResponses;
EngineRequests *engineRequests;
//..
Explanation:
You are using ARC. If you define the pointer locally, as you did before, and to not
retain it - which you can't because of ARC - then it will be released directly after its
creation. You will have to keep at least one reference to the object.
Bare in mind that ARC means Automatic Reference Counting. As soon as there is no
reference to an object it will be released.
This proposal with the engineRequests object defined here only works while you
submit only one request at a time. If you have several requests, i.e. for more than one cell or
whatver, then you may go for a mutable array or mutable dictionary where you keep the requests while you use them.
ViewController.m
#import "EngineResponses.h"
//this is where I set up the delegate/protocol for the parser class
- (void)viewDidLoad
{
[super viewDidLoad];
//..
engineResponses = [[EngineResponses alloc] init];
[engineResponses setMydelegate:self];
engineRequests = [[EngineRequests alloc] init]; // Use instance variable instead of local variable
[engineRequests setEnineResponses:engineResponses];
//..
}
//this is where i set up and call the connection class
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
//..
if(indexPath.section == 0){
//..
if (indexPath.row == 0){
[engineRequests initalizePacketVariables:0 startCode:#"myReg" activationCode:#"myAct" methodName:#"GetStuff"];
//..
}
#pragma - Reciver methods
- (void)sendArray:(NSArray *)array
{
ICMfgFilterArray = array;
[self.tableView reloadData];
}
Explanation: The engineRequets is now an instance varaible and should not be re-defined locally.
You could define a variable of the same name locally which would hide the instance variable. I think
in that case you get a compiler warning but that will work and will most probably confuse you.
Again, if you use more than one request at a time then this solution will not work!
EngineRequests.h
EngineResponses *engineResponses;
EngineRequests.m
#synthesize engineResponses;
//connection delegates etc..
//then I pass the data from the connection delegates over to the parser class
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//EngineResponses *engineResponses = [[EngineResponses alloc] init]; //This Object has already been created!
[engineResponses ReciveResponse:receivedData];
}
Explanation: Here, too, the reference to EngineResponses is now an instance variable, not a locally defined one. The object will not be newly created but it references to that very object that was created in the view controller. That is the one EngineResponses that 'knows' its view controller object and can therefore pass back the parsed data.
EngineResponses.h
#protocol PassParsedData
- (void)sendArray:(NSArray *)array;
#end
//..
id <PassParsedData> mydelegate;
//..
#property (strong) id <PassParsedData> mydelegate;
EngineResponses.m
- (void)parserDidEndDocument:(NSXMLParser *)parser
{
//..
[[self mydelegate]sendArray:filteredArray];
}
... give it a try :)
Always check for nil objects. Sending a message to a nil object will do nothing and your app will continue. I bet this is the problem since you are locally allocing all over the place. Why dont you make the receivedata method a static method instead since it looks like you dont need these classes for more than a few moments for some calculations and parsing. Then nil objects wont be a factor.
I am trying to pass some data back to my view controller from an object class.
This is a basic over view of what classes and views are doing, and then I will show you my code.
So ViewController, loads its tableviewcells. Then inside this delegate method it calles a connection class I have created, inside that conection class is NSURLConnection methods connecting and downloading data from the database, in the connectionDidFinishLoading method of this connection class I set up a parsing class and pass all of the downloaded data over to that.
Then I parse that data, and at the end of that parser inside parserDidEndDocument, I am trying to send the data that is now in an array variable back to my view controller to display. However.. for some reason my protocols and delegates are not working.
I have set up protocols inside m parser class and set the delegates in my view controller but it never makes it to my protocol method.
I will show you my code below.
parserclass.h
#protocol PassParsedData <NSObject>
#required
- (void)sendManufactureArray:(NSArray *)array;
#end
//..
id <PassParsedData> delegate;
//..
#property (strong) id delegate;
//
parserclass.m
#import "VehicleSearchViewController.h"
//..
#synthesize delegate;
//..
- (void)parserDidEndDocument:(NSXMLParser *)parser
{
//.. array stuff is set up and i can log it so i know its working.. i just want to show you the protocol and delegate stuff to be clear
[[self delegate]sendManufactureArray:filteredArray];
}
Then moving onto my view controller where I am hoping to call the protocol and get the filteredArray data back.
ViewController.h
#import "EngineResponses.h" //delegates & protocols
//..
#interface SearchViewController : UITableViewController <PassParsedData> {
//..
Viewcontroller.h
#import "EngineResponses.h"
//..
- (void)viewDidLoad
{
[super viewDidLoad];
//..
parserClass *pc = [[parserClass alloc] init];
[pc setDelegate:self];
//..
}
- (void)sendManufactureArray:(NSArray *)array //Breakpoint here is never accessed
{
FilterArray = array;
[self.tableView reloadData];
}
As you can see in that last method which is the protocol I am calling, its never accessed by the thread. I have checked, This call
[[self delegate]sendManufactureArray:filteredArray];
gets accessed fine.. but it just never makes it back to the View Controller.. any ideas... am I missing anything? .. im at a complete loss, been working on this all day.
any help would be HUGELY appreciated! :)
UPDATE:
I have added this to my ViewController.h
//..
ParserClass *parserclass;
//..
#property (strong, nonatomic) ParserClass *parserclass;
//..
viewcontroller.m
#synthesize parserclass;
//..
//then I call this in viewdidload
[engineResponses setDelegate:self];
As others have said in the comments, your pc variable is being deallocated at the end of the viewDidLoad block, since the only reference it has goes out of scope there. If you want it to live on, you must enlarge its scope (i.e. make it an instance variable).
Another case of protocol method not being called - NO idea what am I doing wrong here...
Here is the code, omitting unnecessary info...
first header file: AccessNumber.h
#protocol AddItemDelegate <NSObject>
#required
- (void) processSuccessful: (BOOL)success;
#end
#interface AccessNumber : UIViewController <UITableViewDelegate, UITableViewDataSource, ABPeoplePickerNavigationControllerDelegate, UIAlertViewDelegate> {
id <AddItemDelegate> delegate;
}
#property (retain) id <AddItemDelegate> delegate;
#end
first .m file: AccessNumber.m - I am calling the protocol method from viewdidload just for testing purposes, it should basically get called from another method, but same thing for the sake of this convo (tried both of course)
#import "AccessNumber.h"
#import "History.h"
#synthesize delegate;
- (void)viewDidLoad
{
[super viewDidLoad];
....
[[self delegate] processSuccessful:YES];
}
second file header: History.h
#interface History : UIViewController <UITableViewDelegate, UITableViewDataSource, AddItemDelegate> {
....
}
method implementation in history.m
- (void) processSuccessful: (BOOL)success {
NSLog(#"SUCCESS");
}
Appreciate any help. Thanks!
In the code i don't see something like:
theAccessNumber.delegate = self;
You must set the History instance as the delegate property of the AccessNumber instance.
Regards.
The code seems a little bit funny but you are not telling your "AccessNumber" class who is his delegate, even though you are making the "History" class implement the protocol established by yourself (otherwise you would get a warning).
You have to set the delegate for the "AccessNumber" class like this when setting it up from within "AccessNumber.m":
self.delegate = historyInstance;
or like this when setting it up from within "History.m":
accessNumberInstance.delegate = self;
There are very vew situations where you should retain a delegate, normally your delagate will outlive the object. So change your property from retain to assign. And be sure you are setting the delegate. Where are you doing it? If your object really depends on it you should be passing it in the constructor (iniWithDelagate). Try doing a NSLog before calling the delagate method just to see if it isn't nil.