I am new to IOS programming. So far I have been programming in android. So in android when pressing a button code for passing an argument would be like that:
Intent i = new Intent(MainScreen.this,OtherScreen.class);
Bundle b = new Bundle();
b.putString("data_1",data);
i.putExtras(b);
startActivity(i);
and on the activity that opens, i would write something like this:
Bundle b = getIntent().getExtras();
ski_center=b.getString("data_1");
what methods should I need to change in MainScreen and in OtherScreen in IOS to achieve the above.
Basically I will have 3 buttons lets say in my MainScreen and each of it will open the Otherview but each time a different parameter will be passed.
Foe example for each button i have code like these in MainScreen.m
#synthesize fl;
-(IBAction) ifl:(id) sender {
}
So I need your help in where to place the "missing" code, too.
Declare an iVar for your UIViewController ( Android's Activity) like a property in Java.
In MainViewController.m
OtherUIViewController * contr = [[OtherUIViewController alloc] initWithNibname...];
contr.data = yourData;
Edited: added full code...
Intent i = new Intent(MainScreen.this,OtherScreen.class);
Bundle b = new Bundle();
b.putString("data_1",data);
here the MainScreen is the calling code, now in iOS it will be the MainUIViewcontroller
create a OtherUIViewController like this:
OtherUIViewController.h
#interface OtherUIViewController : UIViewController
{
NSData* data;
}
#property (strong, nonatomic) NSData* data;
in the OtherUIViewController.m
#implementation OtherUIViewController.m
#synthetize data;
// override
- (void)viewDidLoad
{
[super viewDidLoad];
// do something with data here
}
to have the 3 different behaviors, the data can be an int, or an NSString.
And in the - (void)viewDidLoad you will check the data value and do 3 diff things.
I hope it helps
Related
I'm new to objective C and design patterns like MVC, protocols and so on but this is it:
I am trying to write an iOS app within two viewcontrollers: the first has a textview where the user can write into, and the second has a UISwitch that triggers on "Value changed" and saves a file.
If I toggle by hand the switch on the SecondViewController it will save the file and that's ok.
But I wish the file could be saved from the FirstView just when the user types a specific word, it auto-switches to the second view, and auto-activates the UIswitch and all the method already behind it.
I still can't get the two interfaces working this way. Thanks everybody in advance for helping. Cheers!
this is connected in SecondViewController.h in the storyboard
-(IBAction)toggleFileSave:(id)sender;
and it is implemented as usual...
#interface SecondViewController ()
#property (nonatomic,weak) IBOutlet UISwitch *mySaveFileSwitch;
#end
- (void) toggleFileSave:(id)sender {
// how do I execute this code when the user
// type a specific word in the first view??
}
Create a BOOL flag in your SecondViewController.
Set it when the specific word is typed and push the view controller.
In the viewDidLoad of SecondViewController check the flag condition.If it is set call the required method.
When the specific word is typed:
ViewController2 *viewController = [ViewController2 alloc]init];
viewController2.flag = YES;
[self.navigationController pushViewController:viewController2 animated:YES];
In your text field delegate (add one if it doesn't exist) add this method:
- (void)textFieldDidEndEditing:(UITextField *)textField {
/* at this point the user finished editing */
NSString *currentText = /* read text field value */
if ([currentText isEqualToString:/* the magic word */]) {
/* save the file, present a view controller, etc. */
}
}
Check UITextFieldDelegate to know the available methods, you may need more than one to get the desired behaviour.
If you want to load the second view controller in order to show the UI and the save the file you can do as サンディープ said in his or her answer:
SecondViewController *controller = [SecondViewController new]; /* init as usual */
controller.saveOnLoad = YES;
[self.navigationController pushViewController:controller animated:YES];
Then, in SecondViewController:
- (void)viewDidLoad {
if (self.saveOnLoad) {
/* save file in async block */
/* set switch on */
}
}
If you don't need to show the second view I'd move the saving functionality to its own class and use it from the first controller, showing just a confirmation message for instance.
I created a singleton in ios7 like this:
SharedData.h
#interface SharedData : NSObject
{
}
+ (id)sharedInstance;
#property (strong, nonatomic) NSMutableArray *list;
#end
SharedData.m
#import "SharedData.h"
#implementation SharedData
#synthesize list;
// Get the shared instance thread safe
+ (SharedData *)sharedInstance {
static dispatch_once_t once = 0;
static SharedData *sharedInstance = nil;
dispatch_once(&once, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
- (id)init {
self = [super init];
if (self) {
//initialize
list = [[NSMutableArray alloc] init];
}
return self;
}
#end
I always use this code to access this class:
SharedData *sharedData = [SharedData sharedInstance];
The problem is now when I switch the view in my viewDidLoad method the list is empty but in my viewDidAppear method everything is fine. Any ideas?
EDIT:
This is the code how I change the views:
SharedData *sharedData = [SharedData sharedInstance];
//clear feed and add new feed
[sharedData.list removeAllObjects];
[sharedData.list addObjectsFromArray:newList];
//show new gui
[self.navigationController performSegueWithIdentifier:#"goToMain" sender:self];
NOTE: I push from a normal ViewController to a TabBarController -> NavigationController -> TableViewController to display the list.
I guess you have the confusion between these two viewcontroller methods:
-(void)viewDidLoad{
//
}
&
-(void) viewDidAppear{
//
}
viewDidAppear is the method which is called each time your view changes but viewDidLoad is the method which is not necessarily called each time your view changes.
ViewDidLoad method is called when view loads for the first time, after that it doesn't get called until the views are removed/released.
P.S: I suggest you to put the breakpoint in your viewDidLoad and viewDidAppear method and feel it. Your answer lies there.
Hope this helps you alot.
Good Luck.
The problem was i created a segue which went from the button to the next view. Because of this the viewDidLoad gets earlier called than the list assigned. I just changed the segue to go from view to view.
How are you changing from one viewController to the other? Wich classes are the parents of your destination ViewController?,
If you are modifying properties of the view in the prepareForSegue method... you are forcing the view to load.
For example, you are setting the list of your singleton in prepareForSegue, but before setting the list you are modifying a property of your destination viewController. (doing something like destVC.view = XXX or destVC.viewControllers = XX if you are subclassing a UITabBarViewController...) Then you are triggering the viewDidLoad method , and it's executing before you have set the list to the correct value.
Or maybe you are seguing in two different places to the destinationViewController. And when the viewDidLoad happens, you still have not updated the list on the singleton.
Here is the transcription of the chat with the poster of the question: https://chat.stackoverflow.com/transcript/55218
Hy I have a problem accessing variables in another class.
Im making an app that makes note and let you study from the notes you make, for example the user makes a note that says "Oceanic dolphins: are members of the cetacean...", and when the user press a button to study it appears something like this "what are Oceanic Dolphins" then the user press a button it appears something like this "they are members of the cetacean..." the problem I have is this When i enter the ViewController that makes the question it appears empty I think the problem lies on one of the next codes
I make the Variable Globals like this
QueRes.h
#import <Foundation/Foundation.h>
#interface QueRes : NSObject
#property NSString *question;
#property NSString *response;
#end
QueRes.m
#import "QueRes.h"
#implementation QueRes
#end
I divide the NSString of the note like this
NSArray *card = [_argumentTextView.text componentsSeparatedByString:#":"];
QueRes *make = [[QueRes alloc] init];
if ([card count] >= 2)
{
make.question = card [0];
make.response = card [1];
}
the I apply the variable question and response in a ViewController like this
- (void)viewDidLoad
{
[super viewDidLoad];
QueRes *make = [[QueRes alloc] init];
_questionTextView.text = make.question;
}
then in other view controller i have the same code but apply with the response variable
Please help me I been stuck in this for weeks (I have Xcode 5 and the app runs in IOS 7)
(if you need more of the code of the program to help me fix it just tell me )
You are making a new instance of a QueRes in your viewDidLoad method. Unless the init method of QueRes sets its question and response properties to something, they will be uninitialized, which is why you are not seeing anything in your text view: there is nothing to show.
Naming the QueRes instance you make in the third code block you posted make does not make it the same instance as the instance in the viewDidLoad method, and it is not a global variable at all. It is a separate instance of QueRes.
I have an application where A View Controller (A)is called twice in close succession. Now each time it is called, an NSString object is created, and I need this value to be stored in an NSMutableArray that is a public property of ANOTHER View Controller (B).
In A, I create an instance of the second View Controller (B), and using that instance, add the NSString objects into the NSMutableArray which I've created as a public property. Later, when I am inside View Controller B and print the contents of the NSMutableArray property, the array is empty. Why? Here is the code that is inside View Controller A:
-(void)viewDidLoad {
ViewControllerA *aVC = [[ViewControllerA alloc] init];
if (aVC.stringArray == nil) {
aVC.stringArray = [[NSMutableArray alloc] init];
}
[aVC.stringArray addObject:#"hello"];
[aVC.stringArray addObject:#"world"];
for (NSString *wow in aVC.stringArray) {
NSLog(#"The output is: %#", wow);
}
}
Inside my View Controller B class, I have the following code:
- (IBAction)buttonAction:(UIButton *)sender {
NSLog(#"Button selected");
for (NSString *test in self.stringArray) {
NSLog(#"Here are the contents of the array %#", test);
}
}
Now the buttonAction method gets called, as I do see the line Button selected in the system output, but nothing else is printed. Why? One thing I want to ensure is that View Controller A is called twice, which means I would like to see in the output, "Hello World", "Hello World" (i.e. printed twice), and not "Hello World" printed just once.
The other thing I wish to point out is that View Controller B may not be called at all, or it may be called at a later point in time. In any case, whenever View Controller B is called, I would like to have the values inside the array available, and waiting for the user to access. How do I do this?
Your approach is not ideal, potentially leading to a memory cycle, with two objects holding strong pointers to each other.
You can instead achieve your goal in two ways;
Delegate Protocol
This method allows you to set delegates and delegate methods to pass data back and forth between view controllers
in viewControllerA.h
#protocol viewControllerADelegate <NSObject>
- (void)addStringToNSMutableArray:(NSString *)text;
#end
#interface viewControllerA : UIViewController
#property (nonatomic, weak) id <viewControllerADelegate> delegate;
in viewControllerB.m
// create viewControllerA class object
[self.viewControllerA.delegate = self];
- (void)addStringToNSMutableArray:(NSString *)text
{
[self.mutableArray addObject:text];
}
in viewControllerA.m
[self.delegate addStringToNSMutableArray:#"some text"];
Utility Classes
Alternatively you can use a utility class with publicly accessible methods (and temporary data storage). This allows both viewController classes to access a shared data store, also if you use class methods, you don't even need to instantiate the utility class.
in XYZUtilities.h
#import <Foundation/Foundation.h>
#interface XYZUtilities : NSObject
+ (void)addStringToNSMutableArray;
#property (strong, nonatomic) NSMutableArray *array;
#end
in XYZUtilities.m
+ (void)addStringToNSMutableArray
{
NSString *result = #"some text";
[self.array addObject:result];
}
+ (NSArray)getArrayContents
{
return self.array;
}
in viewControllerA.m
NSString *stringFromObject = [XYZUtilities addStringToNSMutableArray];
in viewControllerB.m
self.mutableArray = [[NSMutableArray alloc] initWithArray:[XYZUtilities getArrayContents]];
I'm not sure what kind of a design pattern you are trying to follow but from the looks of it IMHO that's not a very safe one. However, there are many, many ways this could be accomplished.
One thing though, you said that View Controller B may never get allocated and if it is alloc-ed, it will be down the road. So you can't set a value/property on an object that's never been created.
Since you already aren't really following traditional patterns, you could make a static NSMutableArray variable that is declared in the .m of your View Controller B Class and then expose it via class methods.
So it would look like this:
viewControllerB.h
+(void)addStringToPublicArray:(NSString *)string;
viewContrllerB.m
static NSMutableArray *publicStrings = nil;
+(void)addStringToPublicArray:(NSString *)string{
if (publicStrings == nil){
publicStrings = [[NSMutableArray alloc]init];
}
if (string != nil){
[publicStrings addObject:string];
}
}
Then it would be truly public. All instances of view controller B will have access to it. This, of course is not a traditional or recommended way of doing it—I'm sure that you will have many replies pointing that out ;).
Another idea would be to use a singleton class and store the values in there. Then, when or if view controller B is ever created, you can access them from there.
I am writing the iPhone application and I would like to ask about the the passing parameters in Objective-C.
I create 2 view controller. In the first one, I have a button, when a user press the button, it will call the -(IBAction) pressButton (user-defined), and after 5-6 second (have to process and retrieve the data in the NSMutableArray *), it will display a table. However, I don't know how to pass the NSMutableArray to the table class. Can I do this?
// situation
// ---------------------------------------------
// In MyViewController.m
// class variable
NSMutableArray * arr;
- (IBAction) pressButton: (id)sender {...}
// I retrieve the data and store in the arr
// In TableView.m
// I want to pass the arr to here and use
I know how to create the table, but I don't know how to pass the parameters from a class (MyViewController.m) to another class (TableView.m).
In TableView.h, declare a method:
- (void)doWhateverWithArray: (NSArray *)anArray;
In TableView.m, implement the method to do whatever you need it to do.
In MyViewController.m, near the top of the file (outside of #implementation ... #end) write #import "TableView.h"
Send -doWhateverWithArray: to your table view when necessary.
Function calls are a fundamental part of procedural programming languages like C; message dispatches (AKA method calls) are a fundamental part of object-oriented programming languages like Objective-C.
The nature of this question suggests you're just starting to get into programming (if I'm wrong, please don't take this as an insult--it's not.) I'm sure folks can recommend any number of introductory texts to C or Objective-C, but I'd go further if I were in your shoes.
If available to you, I recommend that you take college-level programming courses, or even enroll in a computer science degree at the university level if you have the time and dedication. :)
In your TableView ViewController create NSMutableArray like this
IBOutlet NSMutableArray *PassedArray;
#property(nonatomic,retain) NSMutableArray *PassedArray;
#synthesize PassedArray;
[PassedArray release];
Now you can pass NSMutableArray value from your Myviewcontroller to tableviewcontroller using this
tableviewcontroller *objInstance = [[tableviewcontroller alloc]initWithNibName:#"tableviewcontroller" bundle:nil];
objInstance.PassedArray = NSMutableArray;//Here you declare your passed NSMutableArray
[self.navigationController pushViewController:objInstance animated:YES];
[objInstance release];
Another method is Declare NSMutableArray *yourArray is global in MyViewController.h and extern those variables in tableviewcontroller.m like this
extern NSMutableArray *yourArray;