I have been given a project to edit. I think this is a simple question but want to explain it in detail.I usually set up iPhone projects with interface builder and then have a view controller h and m file.
However this has been set up in a different way I am new to, the view has been coded.
The h file is a simple viewcontroller class like this:
#interface MainViewController : UIViewController
{
}
- (id)init;
#end
And then the m file has this:
#interface MainView : UIView
{
NSUinterger firstinterger;
}
- (id)initWithImages:(NSArray *)inImages;
#end
And then it has the #implementation MainView just after that with lots more code.
Further down however is where I need to add my code just after
#end
#implementation MainViewController
But I need to access the NSUinterger named first integer and I am unable to. I have tried a few ways of synthesizing etc. but I think I am doing it wrong. How I would get the value of it? I can access it in the code before the #implementation MainViewController but not after which is where I need it.
Synthesize the variable in MainView. Have an instance of the MainView in MainViewController and then you can access it by
MainView *mv = [[MainView alloc] init];
mv.firstInteger // gives you the variable.
NSUinterger firstinterger in your code shows no ';' at the end of that line, do you get compilation errors or is it just a typo in your question?
Related
How can I access the value from an inputField located in a second viewController?
The class name of the second view controller is SettingsViewController and the outlet name for the inputField is setRateInput.
I tried this but it didn't work…
double taxRateFromInput = [[self.settings.setRateInput text]doubleValue];
when I NSLog it comes out as The value is: (null)
Any idea what I'm doing wrong?
Here is the implementation file for the main viewController:
#import "SettingsViewController.h"
#interface ViewController ()
#property (strong, nonatomic) SettingsViewController * settings;
#end
#implementation ViewController
// lazy instantiation
-( SettingsViewController *) settings
{
if (_settings == nil) {
_settings = [[SettingsViewController alloc]init];
}
return _settings;
}
- (IBAction)calculatePrice:(id)sender {
double taxRateFromInput = [[self.settings.setRateInput text]doubleValue];
#end
In theory, you could create a global. Create a new class, call it something like taxRate (.h and .m)
In taxRate.h, add the following code:
#import <Foundation/Foundation.h>
#class MyTaxRate;
#interface TaxRate : NSObject {
}
#property (nonatomic, retain) double * taxRateFromInput;
+(TaxRate*)getInstance;
#end
Then, in your controller, put a "#import taxRate.h" in there. In your .m file, add the following:
#import "TaxRate.h"
#implementation TaxRate
#synthesize taxRateFromInput;
static TaxRate *instance =nil;
+(TaxRate *)getInstance
{
#synchronized(self)
{
if(instance==nil)
{
instance= [TaxRate new];
}
}
return instance;
}
#end
Note: This is extremely similar in structure to what I'm purposing.
if you have the reference from the object view controller you can just access by the property from your attribute.
You instantiated a new SettingsViewController, but you didn't do anything to instantiate its textfield setRateInput. You can do it when you instantiate it:
_settings = [[SettingsViewController alloc]init];
_settings.setRateInput = [UITextField alloc] initWithFrame:someFrame]];
or, as a beter solution, instantiate the text field in -init of SettingsViewController
- init {
if (self = [super init] {
self.setRateInput = [UITextField alloc] initWithFrame:someFrame]];
}
return self;
}
If you use nib files, this would be a lot easier.
Note: setRateInput is a bad name for a property. Consider rateTextField instead.
Edit I forgot to add that you have to add the text field as a subview to its parent view.
So it will be like,
_settings = [[SettingsViewController alloc]init];
_settings.setRateInput = [[UITextField alloc] initWithFrame:someFrame] autorelease];
[_settings.view addSubView:_settings.setRateInput];
In this case, the setRateInput is retained by its super view. You're not using ARC, so you can call autorelease on your text field.
The better solution: Use - (void) loadView; inside SettingsViewController. Loading the view is the responsibility of the correspondent view controller.
- (void) loadView {
self.setRateInput = [[UITextField alloc] initWithFrame:someFrame] autorelease];
[self.view addSubView:_settings.setRateInput];
}
Edit: xib files and storyboards can help you out. Give these tutorials a try.
You are on the right track, also well done with your lazy instantiation (as
a demonstration that you grasped the concept, I mean).
But note, that outlets don't get connected until viewDidLoad is called. So if you
just alloc/init your viewController (lazily), the outlet to your textfield is pointing to nil.
The outlet doesnt get connected until your controller's view property is accessed, ie the view is displayed.
What you could do is give the settings viewController a handle to your calculating viewController and let it set a public property on the calculating viewController that represents the rate.
This is a common pattern - delegation - where one viewController (settingsViewcontroller) calls a method on its delegate (calculating viewController).
You wouldn't need the settingsViewcontroller property in your calculating viewController then, but just instantiate a new settings viewController every time you want it to be brought up, giving it a reference to your calculating viewController.
Another possibility - maybe even better - is to define a model object that does calculation and takes care of the rate it needs to calculate. Then you could give your settingsViewcontroller a reference to that model object (probably instantiated in your
other viewController), so that it can change the rate on it.
PS: also re think how you instantiate viewControllers generally. The designated initialiser is -initWithNibName:bundle: - so usually, you wouldn't just alloc/ -init them.
If you use storyboards (you probably should!), use storyboard's -instantiateViewControllerWithIdentifier: or use the above mentioned designated initialiser.
i've been doing a thing here using objective-c, but i'm a beginner in this language, and that's what i did:
there is a class, named "firstviewclass", that is in the control of my first view, in this view there is a textfield that the user puts a number. the textfield is in the firstviewclass.h named "setNumber". There is another class, named "secondviewclass" that is in control of the second view, in this view there is a label that is in the secondviewclass.h, and i want that this label recive the value that the user put in the textfield from the first view, but when i test it on the iOS simulator any number that i put in the textfield it appears in the label as 0... I really don't know what to do!
My codes:
firstviewclass.h:
#import <UIKit/UIKit.h>
#interface firstviewclass : UIViewController
#property (strong, nonatomic) IBOutlet UITextField *setNumber;
- (IBAction)gotonextview:(id)sender;
#end
secondviewclass.h:
#import <UIKit/UIKit.h>
#import "firstviewclass.h"
#interface secondviewclass : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *labelthatrecivesthetextfieldvalue;
#end
secondviewclass.m:
#import "secondviewclass.h"
#import "firstviewclass.h"
#implementation secondviewclass
#synthesize labelthatrecivesthetextfieldvalue;
-(void)viewDidLoad{
[super viewDidLoad];
firstviewclass *object = [[firstviewclass alloc] init];
NSString *string = [[NSString alloc] initWithFormat:#"%i", [object.setNumber.text intValue]];
labelthatrecivesthetextfieldvalue.text = string;
}
#end
First of all, I would strongly recommend not naming a property or instance variable setSomething. It will cause headaches for anyone reading your code because it will always look like you're trying to call a setter. Also, please do capitalize your class names.
Your actual problem is that in viewDidLoad you're creating an instance of firstviewclass, and then trying to get the value from setNumber. That is before the user had any chance to enter anything.
Also, the setNumber outlet in firstviewclass will probably be going nowhere anyway, since you're instantiating that class yourself, instead of loading the NIB.
Edit (ah, Storyboard, d'oh):
For Storyboard, you need to pass the setNumber text field's value to the second view.
First of all, remove the firstviewclass *object = [[firstviewclass alloc] init]; line.
Then, in your first view controller's prepareForSegue method, you can pass the value of the setNumber text field to a property in your your second view controller, and use it from there (e.g. in configureView).
I recommend working through Apple's Storyboard tutorial, it shows exactly what you need to do, step by step. The step you're having issues with right now, passing data to your next view controller, is here.
How are you initiating the setting of the label? From viewDidLoad? If so, then 0 would be correct because you have not set object.setNumber.text to anything. Also, you aren't carrying over the data from your first viewController. You need to let the second viewController know what the number is. Try setting this value in your NSUserDefaults, then in your second viewController, load that value from your defaults.
in the viewDidLoad of secondviewclass, you are creating a new instance of firstviewclass, and then accessing the property of the label. Since you haven't set that to be anything, it will always return zero.
Can you post the implementation of the gotonextview method?
EDIT:
I think you need to be setting the label property from the first view controller. so in your gotonextview method, add this line:
secondviewclass.labelthatrecivesthetextfieldvalue.text = self.setNumber.text;
I admit I'm a little lost in your naming scheme but that might work.
I have 2 view controllers now, And it both got tableviews.
When I choose a row in the second tableview (Using didSelectRowAtIndexPath),
and I want to pass the Information I got in the second View to the first View,
I tried to use delegate&protocol, but don't know why, It didn't work.
And I tried to use class method inside the first class, when I got variable in sencond View,
Call the class method inside the first class. The variable successfully pass to first View,
but when I want to set the Lable's text, it still failed..
Can somebody teach me how to do? thanks!
My protocol&delegate.
This is the second view.
#protocol CategoriesViewControllerDelegate;
#interface CategoriesViewController : UIViewController {
TableViewNewAppDelegate *appDelegate;
id <CategoriesViewControllerDelegate> delegate;
}
#property (nonatomic, assign) id <CategoriesViewControllerDelegate> delegate;
#end
#protocol CategoriesViewControllerDelegate <NSObject>
-(void)backstring:(NSString *)String;
#end
In the .m file , synthesize it
#implementation CategoriesViewController
#synthesize delegate;
didSelectRowAtindexPath
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
CategoryData *CateObj = [appDelegate.CateArray objectAtIndex:indexPath.row];
NSString *Strings = [NSString stringWithString:CateObj.CateTitle];
[delegate backstring:Strings];
[self.parentViewController dismissModalViewControllerAnimated:YES];
}
In the first view controller .h file.
#import "CategoriesViewController.h"
#interface DataController : UIViewController <CategoriesViewControllerDelegate>{
.m file
-(void)backstring:(NSString *)String {
NSLog(#"%#",String);
jCateField.text = String;
}
This is how I do my protocol+delegate. Are there something wrong?
btw, I created a Class method in the first view controller, and use the Class method in the sencond view controller, it succesfully pass variable to first view controller.
But the problem is, I can't set my Label's text inside my Class method, even calling Instance method to set text. Is there any way to solve this problem?
The code you provided seems to be correct. In your case you must set :
#property (nonatomic, assign) id <CategoriesViewControllerDelegate> delegate;
correctly to point to the first view controller which conforms to the protocol you defined :
#import "CategoriesViewController.h"
#interface DataController : UIViewController <CategoriesViewControllerDelegate>{
So it seems that you pushed a CategoriesViewController onto a first DataController, you probably missed to do so just before.
// self is the first view controller
// [myCategoriesViewController setDelegate:self]; old fashion
myCategoriesViewController.delegate = self;
[self presentModalViewController:myCategoriesViewController animated:YES];
This can probably solve your issue. Hope this helps.
Also consider let the first controller dismiss the second.
Here is a link to Apple's documentation.
You could just pass the information straight on to your second view controller;
SecondViewController.h
#interface SecondViewController
{
Information *info;
}
#property (nonatomic, retain) Information *info;
#end
SecondViewController.m
#implementation SecondViewController
#synthesize info;
...
#end
And in your didSelectRowAtIndexPath method;
SecondViewController *controller = [[SecondViewController alloc] initWithNibNamed:#"SecondViewController" bundle:nil];
[controller setInfo:YOUR_INFO_OBJECT];
[self.navigationController pushViewController:controller animated:YES];
[controller release];
Import second view controller header file in the first view controller implementation file. Import first view controller header file in second view controller header file.
Create the property (text/label/whatever) in the first view controller.
Create the property of first view controller in the second view controller.
Create the second view controller instance, set the first view controller property to what you need, push controller to the navigation controller. In the second view controller change whatever you want in the first view controller. Instance methods allowed. Do not forget to release first view controller.
Delegate pattern works in that way too.
View controllers are objects. Objects can have methods that can be called from other objects, and they can have instance variables. ("Delegate" is just a fancy term for this.)
There's no inherent reason why passing data between your view controllers should be hard or complicated, so long as the caller has the address of the callee. (And whether or not a given VC has an XIB is irrelevant.)
It sounds like your real problem is not knowing what to do with the data once it's been passed to the callee.
Stupid question: Is "jCateField" actually connected to the label you want to change, or is it nil? If you created the label from code (since you don't have an XIB), you will need to have stored the created label's address into "jCateField" during the view creation.
Can you post the code for as to ho you are displaying the contents when you come back to 1 st view controller.As here if the log gives you proper value then the issue is with the connection (if taken through iboutlet) or with addsubview .
Do you get nil in label or no value (label is hidden).
I'm trying to set a variable in another view.
I'm in a view which I have named ProgramViewController and from here I would like to set a variable named bands in MyViewController.
I thought it would be as simple as
MyViewController *myViewController = [[MyViewController alloc] init];
myViewController.bands = #"hello world";
[myViewController release];
And in the header of MyViewController:
#interface MyViewController : UIViewController <UITableViewDataSource, UITableViewDelegate> {
NSString *bands;
}
#property (nonatomic, retain) NSString *bands;
That does not work, though.
Can anyone please tell me what I am doing wrong?
EDIT:
I synthesize bands in MyViewController:
#synthesize pageNumberLabel, tableProgram, bands;
But when trying to print it with NSLog in the viewDidLoad of MyViewController I get (null)
NSLog(#"%#", bands);
You need to synthesize the bands variable in MyViewController.m
#synthesize bands;
A variable needs to be synthesize in order to use it as a public property outsize of a class in Objective-C
I solved this in another way. I managed to load the data in MyViewController instead. I was dealing with a page controller and had to populate a UITableView but had troubles loading the data.
This is solved in a completely other way now.
I've been banging my head with this one this evening and am sure it's something very simple that I've missed
I've created a new project with the appdelegate and a view controller class as below. The view controller synthesises the property in the .m, and the app delegate header imports the view controller .h file. Code below:
View controller header:
#interface untitled : UIViewController {
NSString *string;
}
#property (nonatomic, retain) NSString *string;
App delegate:
- (void)applicationDidFinishLaunching:(UIApplication *)application {
testViewController = [[untitled alloc] initWithNibName:#"untitled" bundle:nil];
testViewController.string = #"Testing String";
[window addSubview:testViewController.view];
[window makeKeyAndVisible];
}
Can someone please help and point out the obvious mistake as to why setting the string property fails here with the error mentioned? Is it because of being inside this method? I've never had issues setting properties in other methods before after initing a view controller.
Thanks.
The error is saying it does not understand that the class has that property. It means you have either the wrong class or that it knows nothing about the class.
So, you need to add:
#import "untitled.h"
in your application delegate - also, you need to have the variable be of type "untitled" (I am pretty sure you declared the type as UIViewController and not untitled):
untitled * testViewController = (untitled *)[[untitled alloc] initWithNibName:#"untitled" bundle:nil];
By the way, by convention you should always start class names in uppercase.