I am trying to access a function in an objective C category that extends a UIViewController from the original controller. When I do this one of the properties is nil and the method doesn't work properly. When accessed from inside the category (using a UITapGestureRecogniser) the property has a value in memory and works fine. Am I missing something this seems very odd?
calling from the UIViewController:
[self dismissCurrentPopinControllerAnimated:YES completion:nil];
from the category: (UIViewController_MaryPoppin)
- (void)dismissCurrentPopinControllerAnimated:(BOOL)animated completion:(void(^)(void))completion
{
UIViewController *presentedPopin = self.presentedPopinViewController;
The presentedPopin controller is nil when called from outside the category.
My mistake, it seems that with this category (UIViewController+MaryPoppin) you need to send messages to the presented controller (in this case a UINavigationController) so self was incorrect although the compiler still didn't complain.
[self navigationController]dismissCurrentPopinControllerAnimated:YES completion:nil];
This seems to have solved the problem
Related
I need to pass value from a ViewController to NSObject as soon as the view loaded using Xcode with Objective c.
I am using the code below but the value is null.
-(void)viewDidAppear:(BOOL)animated
{
MyHomeModelNSObject *nsOb;
nsOb = [[MyHomeModelNSObject alloc] init];
nsOb.myString = self.userName.text;
}
The above code is working between Views when using segue, but it does not work with when passing the value to NSObject.
Thanks
The above code is working between Views when using segue, but it does not work with when passing the value to NSObject.
You're not using a real object. You're declaring a pointer to an object, but never allocating the object itself:
MyHomeModelNSObject *nsOb;
nsOb.myString = self.userName.text;
See? You're missing the bit where you do:
nsOb = [[MyHomeModelNSObject alloc] init];
What's more, even if you added that, the object would be deallocated as soon as viewDidAppear exits because it's a local variable. If you want it to hand around, you'll need to 1) create it and then 2) assign it to some property of your view controller or another object.
Probably a noob question, but I cannot seem to get it right at the moment. I am working on an app where I have an Actionsheet for the confirmation of some basic things. However after the delegate is called for that Actionsheet my initial calling object is released (or not initiated).
In the delegate method I then want to call a method on that object but it just not do anything from that point.
The self.inviteSponsorsFromVC is not initiated anymore in this scenario and I want to call the saveSponsorWithEmail method from it. I cannot just reinitiate it, as the object had some objects in it, it has to use.
Everything works correctly if I just remove the actionsheet and call the saveSponsorWithEmail method directly without using a delegate.
This is my delegate method:
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
//Get the name of the current pressed button
NSString *buttonTitle = [actionSheet buttonTitleAtIndex:buttonIndex];
if ([buttonTitle isEqualToString:NSLocalizedString(#"Send invitation", nil)]) {
ContactFromAddressBook *contactFromAddressBook = [self.tableData objectAtIndex:selectedIndex.row];
[self.inviteSponsorsFromVC saveSponsorWithEmail:contactFromAddressBook.email andName:contactFromAddressBook.fullName];
}
if ([buttonTitle isEqualToString:NSLocalizedString(#"Cancel", nil)]) {
NSLog(#"Cancel pressed --> Cancel ActionSheet");
}
}
My guess is that at in the delegate method the content of self.inviteSponsorsFromVC is nil. In Objective-C, when you send a message to nil the message is simply ignored (unlike C++, for instance, where you get a crash when you call a method on a NULL object).
As an experiment you can try either one of these:
If you use ARC, make the property self.inviteSponsorsFromVC a strong reference
If you don't use ARC, say [self.inviteSponsorsFromVC retain] at some point before you display the action sheet
Either way, what you need to do is to make sure that the object in self.inviteSponsorsFromVC is not deallocated before you invoke a method in it.
EDIT after your comment
The property declaration is good, it's got the strong attribute on it. In your InviteSponsorsFrom class, try to add a dealloc method and set a breakpoint there to see if the object is deallocated, and where the call comes from.
- (void) dealloc
{
[super dealloc];
}
Also make sure that an instance of InviteSponsorsFrom is created in the first place. I assume you have an initializer somewhere in that class where you can set a breakpoint and/or add an NSLog statement to make sure that the instance is created.
I'm working to a new app for mac osx where i'm using a drag and drop system to let the user to input some files [this part works well] and i have a tabelView where i would like to display the paths of files inputed.
I have the next method in tabelViewController.m:
-(void)add{
NSLog(#"da");
[list addObject:[[Source alloc] init]];
[tableView reloadData];
}
In the DropView.m i included the tabelViewController.h and i'm trying to call the add method but it does nothing:
#import "TableViewController.h"
.....
- (void)concludeDragOperation:(id<NSDraggingInfo>)sender{
[self setNeedsDisplay:YES];
TableViewController *tvc;
[tvc add];
}
Can someone to figure out why it doesn't do anything ?
Edit1:
Ok after I fallow the answers, my concludeDragOperation method looks like this:
- (void)concludeDragOperation:(id<NSDraggingInfo>)sender{
[self setNeedsDisplay:YES];
TableViewController *tvc = [[TableViewController alloc] init];
[tvc add];
[tvc rD];
}
rD is a method from tableViewController which contain the reloadData method.
But it doesn't want to work it don't reload the table view.
Any ideea ???
tvc needs to point to an actual object. [[tvc alloc] init]
Otherwise you are simply calling add on nil. This doesn't cause your program to crash as you might expect in other languages. Try it out and see what happens.
it seems as if you missed a great chunk regarding how OOP and Objective-C work (seriously, no offense there).
What link is there between DropView.m and tableViewController.h do you have?
By typing TableViewController *tvc; all you are doing is creating a pointer. You are neither creating an object nor pointing to an object, you have just simply created a pointer that can eventually point to an object in memory of type tableViewController.
Solution:
What you will need to do, is to somehow create a link between the two classes. For instance, you could create a custom delegate method for DropView that could communicate with any class who uses that custom DropViewDelegate methods. So, you could create a delegate method that tells objects that follow that delegate protocol that you just concluded a drag operation. A tutorial how to do so can be found at my blog [it's a permalink].
I am happy to post code, or you can read it on my blog. Good Luck.
I did quite a bit of research on this, but I am having a mental block about my problem. I am working on Objective-C for an iOS app
Here's my set up:
The view controller gets a text from the view (user input), and passes that text to the MethodA of the model.
The MethodA in model works on the input text and gets an output (e.g. searches google for that text). It does the search using dispatch_async method which calls the selector to MethodB within model.
MethodB parses the output and puts all the results into a NSMutableArray
My Question Here: how do I pass that NSMutableArray back to view controller so I can show it on the view?
Sorry, if the answer to my question is very simple/obvious. I am new to Objective-C
Any time I want to do async processing and that stuff needs to get back into the UI somewhere, I do one of two things:
1. Use NSNotification to tell anyone who cares that the work is complete
2. Use a delegate property on the worker and a #protocol
1 NSNotification
The model object should document in it's .h file that it fires notifications when certain things happen; such as when a portion of the model has been updated. When the ViewController initializes the model object, have it set itself up as an observer of the documented notification, and implement a callback which updates the UI.
2 delegation and #protocol
Create a #protocol such as #protocol FooModelUpdateDelegate with a method properly named such as fooObjectDidUpdate:(Foo *)object;, and then the model class has a delegate property as id<FooModelUpdateDelegate> updateDelegate and the ViewController sets itself as that delegate, and I'm sure you can figure out the rest.
I guess passing along a delegate-object that respoons to a selector-method and calling this method with the processed data will be a good way to achieve the loosley coupled structure your program deserves. Are you familiar with this concept, or shall I dig up some code-samples for you?
UPDATE: Code samples
So, I would probably use the calling class, say MyViewController, to implement the callbackMethod, myCallbackMethod as follows:
-(void) myCallbakcMethod: NSMutableArray* array {
//DoWhatever with the returned data
}
The point is to get the result passed back to this method when the computation is finished.
So in your MyViewController where you call MethodA you pass along a reference to the delegate to handle the result, namly self.
//From this:
[MyModel methodA:param1]
//To:
[MyModel methodA:param1:self]
MyModels methodA and methodB would need to add a parameter (id)delegate and pass that along between the calls.
In methodB where the data myArray is ready, do the following call:
if([delegate respondsToSelector:#selector(myCallbackMethod:)]])
[observer performSelector:#selector(myCallbackMethod:) withObject:myArray];
In your view controller:
// your controller code
...
[myModel getSearchResult:searchKeyword receiver:self action:#selector(responseReceived:)];
}
- (void)responseReceived:(MyModel *)model
{
NSArray *searchResult = model.searchResult;
[model release], model = nil;
// some view actions, for instance update your table view
...
}
In your model:
...
- (id)getSearchResult:(NSString *)searchKeyword receiver:(id)aReceiver action:(SEL)receiverAction {
self.receiver = aReceiver;
self.action = receiverAction;
// some async actions
}
In async response receiver:
...
[self.receiver performSelector:self.action withObject:self];
}
Unless I'm misunderstanding your description it sounds like your "model" class is doing more than it should. In this case it's doing at least some of the work of your controller. My suggestion would be to fold methodA and methodB into the view controller (or another controller class). Method B could still set the NSMutableArray property of "model" instance, if that's essential (or skip that step if it's not).
-(void)methodA {
NSMutableArray *someArray = ...
[self methodB:someArray];
}
-(void)methodB:(NSMutableArray*)array {
NSLog(#"%#", array);
// do something with the array, like update the view
}
But if both are methods inside the view controller why not just update the view inside the method instead of passing it to another method?
So I have this custom class with just a test method that does nslog. I am going to reuse this method many times in my app. The interface looks like this.
#interface TestViewController: UIViewController { CMImageMover * imageMover }
Then in the view did load I:
imageMover = [[CmImageMover alloc] init];
If I do:
[imageMover testMethod];
Right after the alloc and init it works in the viewDidLoad function but if I call it again from another function in the view controller nothing works and the class method does not get called.
What am I doing wrong here. Every other var I declare like NSArray/NSTimer, I do the say way and I am able to access and use it throughout my controller.
When you say "if I call it again from another function in the view controller nothing works" then first thing to check is what you are sending the testMethod. It could be nil, in which case nothing will happen. In objective C sending a message to nil does nothing. Add an NSLog to find out, e.g.
NSLog(#"imageMover object is: %#", imageOver);
[imageMover testMethod];
If the NSLog shows it is nil - or something crazy - then follow up what you are doing with the imageMover ivar.
You mention a class method in your question, but don't refer to it in your code snippets.
If you have defined testMethod as a class method it will, of course, fail if you send that message to an instance. (And it will fail noisily.) A class method would be introduced like this:
+ (void) testMethod
{
NSLog(#"CMImageMover testMethod called on Class");
}
An instance method would be introduced like this:
- (void) testMethod
{
NSLog(#"testMethod called on an instance of CMImageMover");
}
Apologies if this is all screamingly obvious to you and missing the point of the question. It's not that clear from your question where the issue lies.