passing parameters in prepareForSegue: - ios

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"CreateUser"])
{
CreateUserViewController *createUserVC = segue.destinationViewController;
createUserVC.email.text = #"something from fb";
createUserVC.age.text = #"99";
createUserVC.name.text = #"Name from fb";
}
}
I call this segue from my "StartVC." I have another CreateUserViewController which contains different textfields to hold user details. I have no idea why this wouldn't be working, can someone pls enlighten me?
By breakpoints I can see the code is run, and the create user vc is presented, but the fields are empty(only containing placeholder; I do not write the strings blank by = #"" or anything alike)

You should not try to make changes to another view controller's view objects.
That violates the principle of encapsulation, an important part of object-oriented design. (It means that other parts of your code, outside of your view controller, depend on the PRESENTATION of your view controller in order to work. If you decide to move views around later, you have to change code that's outside of your view controller. That's bad.)
It's also the reason your code isn't working.
Instead you should set up properties in your destination view controller and set those. Then in your destination view controller's viewDidLoad (only invoked once) or in viewWillAppear (called every time the VC is about to be shown) install the values from your properties into your views as appropriate.
At the time prepareForSegue is called the destination view controller's views haven't been loaded yet. If you look at them you'll find that they are nil. That's why your code isn't working.
Try this test:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"CreateUser"])
{
CreateUserViewController *createUserVC = segue.destinationViewController;
NSLog(#"createUserVC.email = %#", createUserVC.email);
NSLog(#"createUserVC.age = %#", createUserVC.age);
NSLog(#"createUserVC.name = %#", createUserVC.name);
}
}
You will see that all of those outlets are nil.

Related

How to make work preparForSegue :sender: XCode 6?

In my app, I use segment to switch in three view. Every segmment represented with container view and they become hidden or appear according to segment. That is how my the design works, and it works well. You can find the picture below, so you can understand the structure more:
I'm having trouble with giving an instance (namely, user) created in the view controller to segment's container's view controller. I created user in the user and assign it the values. user instance has the values, I checked it. So, as usual to give with segue, I tried prepareForSegue:sender method to achieve my purpose. In the viewLoad method of the table views(you can find the table views: each of them are attached to its own container in the view controller that has segment. There are 3 containers.) user instances of table views are null. I can't give it, basically. Shouldn't the view controller pass the user value? It might being container view, but still I think it should be :) Anyway, please find below what I have written so far:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
UINavigationController *navController = (UINavigationController *)segue.destinationViewController;
DovizTableViewController *controller = (DovizTableViewController *)navController.topViewController;
controller.user = self.user;
}
You would remove the sender part of your code.
It should look like this:
- (void)prepareForSegue:(UIStoryboardSegue *)segue{
//your code
//check if the next view exists by checking for the id
if ([[segue identifier] isEqualToString:#"Segue_Name"])
{
DovizTableViewController *controller = [segue destinationViewController];
controller.user = self.user;
}
}
Try this.
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:#"YOUR_SEGUE_NAME_HERE"])
{
// Get reference to the destination view controller
DovizTableViewController *controller = [segue destinationViewController];
// Pass any objects to the view controller here, like...
controller.user = self.user;
}
}
Hope it helps.

IOS - Use Segue identifier in child method

This is probably a basic question - but I cant seem to find the answer to it in my searches!
I have a uiview setup which contains two input areas which are linked to a child modal view via separate segues.
this is my parent prepare for segue method -
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"goalInfo"])
{
[segue.destinationViewController setYourGoalViewController:self];
}
if ([segue.identifier isEqualToString:#"longGoalInfo"])
{
[segue.destinationViewController setYourGoalViewController:self];
}
}
basically i'd like to determine which segue had been used in the child view so I can apply the relevant filed updates and alter a title/description in the child view. - I basically need something very similar to
if ([segue.identifier isEqualToString:#"goalInfo"])
but i'm not sure how to access this from teh child? Any tips?
The segue identifier is check on the source ViewController during its prepareForSegue: method. What you rather need is during prepare for segue is to set properties on the destination viewController and then when it loads, read these properties and set UI outlets.
Look at this example: I am stuck at presenting a full image on tapping the cell in UICollectionViewController. It's about CollectionVC and its detailVC, but the principle is the same.

I can update a BOOL located in a second view controller using the prepareForSegue method but not a Label, why?

I have been trying to have a better understanding on how to pass data between view controllers and everything is make more sense but there is one thing I would like to understand better.
I came across this thread/tutorial here at StackOverFlow (Passing Data between View Controllers), I tried it and it worked as expected, but the one thing I don't know understand is why we can change a BOOL property located in the second view controller but NOT a Label. In other words if I add a second property and try to change the label in the prepareForSegue: method it doesn't work, why?
In section Passing Data Forward using Segue's I tried adding a second property for a label in the second view controller, right where isSomethingEnabled is, like this...
#property(nonatomic) BOOL *isSomethingEnabled;
#property (weak, nonatomic) IBOutlet UILabel *myLabel;
Than in prepareForSegue: method located in the first view controller I did this..
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([segue.identifier isEqualToString:#"showDetailSegue"])
{
ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
controller.isSomethingEnabled = YES;// this works fine
controller.myLabel.text = #"Hello"; // here, no error but it doesn't update the label
}
}
Why you can modify a BOOL property located in a second view controller but not a label? Can someone explain this a little bit?
Thanks a lot
As Grzegorz Krukowski said the UIViewController isn't loaded at that moment. You can set #property values and access them in the viewDidLoad method and setup your Labels accordingly.
First of all, you should not do this. You should treat another view controller's views as private. The reason for this is the concept of encapsulation. A view controller's views are part of the view's appearance, not it's API. If at a future date you decide to refactor the VC so that it uses the text string in question as the title in a navigation controller, you should be free to do this. If another view controller reaches inside your view controller and manipulates it's view objects directly, you must keep those view objects unchanged forever, or you run the risk of breaking the way the other view controller interacts with it. That's bad, and 6 months from now you won't remember that 3 outside view controllers manipulate your view controller's views, and when you forget and change your views and decide to move a piece of text to a different UI object, your app will stop working correctly.
What you SHOULD do is to add a string property to your ViewControllerB, and set THAT in your prepareForSegue. Then in ViewControllerB's viewWillAppear:animated method, fetch the contents of that string property and install it in your label's text property.
Then the string property becomes part of your view controller's API contract (its public interface.) By adding a public string property to your interface, you guarantee that you will accept string values to that property and that you will do the right thing with them.
Now, as to why it doesn't work. A view controller's view hierarchy is not loaded until it's displayed. At the time of prepareForSegue, the view controller has been initialized, but it's views haven't been loaded yet. All its IBOutlets are nil. (this is another reason why you should not try to manipulate another view controller's views BTW)
Your prepareForSegue method looks like this: (wrong)
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"showDetailSegue"])
{
ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
controller.isSomethingEnabled = YES;// this works fine
controller.myLabel.text = #"Hello"; // here, no error but it doesn't update the label
}
}
Instead, your code should look like this:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"showDetailSegue"])
{
ViewControllerB *controller = (ViewControllerB *)segue.destinationViewController;
controller.isSomethingEnabled = YES;// this works fine
controller.textToShow = #"Hello"; //This is the change
}
}
Then, in your ViewControllerB's viewWillAppear:animated method:
- (void) viewWillAppear: animated;
{
[super viewWillAppear: animated];
//install the text from our textToShow property into the label
self.myLabel.text = self.textToShow;
}

Automatic deallocation of view controller on push using storyboard and segue

I am using storyboards with iOS 5 and Xcode 4 and have run into a small problem.
I have a view controller (WallPostViewController) that is the root view controller of my navigation controller. Through the storyboard, I have a segue (called "PushWallPostCommentsSegue") which is performed after the user clicks a button.
When I get to prepareForSegue:sender, I set an object inside the newly pushed view controller.
Code follows:
-(IBAction)addNewCommentButtonTouched:(id)sender {
[self performSegueWithIdentifier:#"PushWallPostCommentsSegue" sender:self];
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqual:#"PushWallPostCommentsSegue"]) {
NSLog(#"Pushing from %# to %#", segue.sourceViewController, segue.destinationViewController);
WallPostCommentsViewController* wallPostCommentsViewController = segue.destinationViewController;
[wallPostCommentsViewController setWallPost:wallPostInfo];
[wallPostCommentsViewController setParent:self];
}
}
The problem is: this view controller is never pushed and is automatically deallocated (even though it has connections in the storyboard and it's own other objects).
Btw, this view controller's initWithCoder: method IS called.
Just can't find the problem here. Any heads up?
Thanks in advance, Ricardo P.

prepareForSegue and delegates

I have an application with two segues. In one of the segues, the current view controller becomes a delegate and the other does not.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"MoreOptions"]) {
UINavigationController *navigationController = segue.destinationViewController;
MoreOptionsViewController *controller = (MoreOptionsViewController *)navigationController.topViewController;
controller.delegate = self;
} else if ([segue.identifier isEqualToString:#"FullStoryView"]) {
SingleStoryViewController *detailViewController = segue.destinationViewController;
detailViewController.urlObject = sender;
}
}
All of this is working fine, but I would like to try and understand the code better. What I don't understand is that I have to get a reference to the MoreOptionsViewController by grabbing it from navigationController.topViewController rather than simply getting it from segue.destinationViewController like I do in the second if condition. Is it because I'm setting the current view controller (self) as the delegate? Again, I'm not trying to solve a problem, just trying to get a better understanding of what's going on.
Take a look at your storyboard and it should be evident why this is the case. You have embedded MoreOptionsViewController in a UINavigationController and connected a segue to the navigation controller, thus making it the destinationViewController. This is fairly common.
The delegate is largely irrelevant in the context of your question.
Your first segue's destination is a navigation controller, which contains the view controller you are really interested in. Therefore to get to that view, you need to go through the navigation controller since that won't have any properties you are interested in setting.
Your second segue goes directly to a single view controller, so you can access it directly.

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