Is it possible to assign a text tag to any UIObject? If not is there another way I can do it? Can I do for example:
image.tag = [NSString stringWithFormat: #"Hello"];
Thanks for any help!
The tag property is an NSInteger - therefore this is not possible.
You can create a subclass and add an NSString property.
No, the tag is an integer.
Consider subclassing UIImageView class and just adding a NSString property. It is really simple these days.
Example:
#interface TaggedImageView : UIImageView
#property (nonatomic, strong) NSString *tagString;
#end
#implementation TaggedImageView
#end
Then just use TaggedImageView in place of UIImageView.
If you only access the MyImageView from one .m file you can just put these lines just after the #import statements.
Related
.h file
#import <UIKit/UIKit.h>
#interface calculatorViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *display;
#end
.m file
#import "calculatorViewController.h"
#interface calculatorViewController ()
#end
#implementation calculatorViewController
#synthesize display=_display;
- (IBAction)digitPressed:(UIButton*)sender
{
NSString *digit=[sender currentTitle];
NSLog(#"digit pressed %#", digit);
UILabel*myDisplay=self.display;
//[self display] why not just type
NSString *currentText= myDisplay.text;//[myDisplay text]; why are we not writing current title again?
nsstring*newText=[currentText stringByAppendingString:digit];
[myDisplay setText:newText];
Hi guys!
I have been trying to learn Objective-C so these questions might be stupid for you but tough for me, so please do not down vote my question as I am only trying to learn like you. :)
I have a couple of questions in .m file.
(IBAction)digitPressed:(UIButton*)sender Does (UIButton *) mean that it is a type and that sender is a pointer simultaneously? Cant we remove the bracket?
NSLog(#"digit pressed %#", digit);Why does this not work with *digit. Doesn't digit only store the address and not the actual value?
UILabel*myDisplay=self.display; I know self.display is a getter but what exactly is selfWhen do we use it?
NSString *currentText= myDisplay.text Why are we writing .text and not currentTitle like in NSString *digit=[sender currentTitle];
Lastly I read a lot but could not understand. In one sentence what is the difference between NSString and UILabel?
(UIButton*)sender means that the sender is passed in the parameter of the method, and that sender is casted to a UIBUtton object.
Because *digit is a pointer to an object, so that will print the memory address of the object
You use it if you want to access the variable trough the getter, and not directly the instance variable.
Is the same, is just a convention, use . to access properties and space to access methods.
NSString represents a string object like "ABC", UILabel is a view that will be displayed in your screen, and which text is a NSString.
I won't go into more details, as SO is not a tutorial page. You'll find all this answers in the first chapter of any CocoaTouch programming book.
(UIButton *) is a typecast to a UIButton object. If you are sure that the sender is a UIButton you can add the typecast. In that way you can directly access the properties/methos on the UIButton object
2.
As far as I understand digit refers to the string object. And *digit means the first (located at index 0).
3.
self means the class it self i.e. calculatorViewController
4.
text is a property of UILabel component
5.
You cannot display a NSString on the display itself you need a UILabel component. You can set the text property to a NSString object and display it on the screen
regards
Johan
I would like to set a value of my array to a label.
Array declaration:
//
// ViewController.h
// Cornell Notes
//
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController{
NSString *details[8][8];
NSString *subtitles[8];
}
I am not allowed to do:
self.label.text = subtitles[0];
How can I do this?
This:
#interface ViewController : UIViewController{
NSString *details[8][8];
NSString *subtitles[8];
}
Should Be:
#interface ViewController : UIViewController
#property (strong, nonatomic) NSMutableArray *details;
#property (strong, nonatomic) NSMutableArray *subtitles;
You could declare it similar to the way you had it, but I believe this is the preferred current syntax. Others may correct me on this. Most important is that we declare NSMutableArray's as opposed to NSString's. You are doing C-style declarations, which will be a bit different with these. I chose NSMutableArray as opposed to NSArray because it looks like you want to be able to add objects at runtime.
And this:
self.label.text = subtitles[0];
should be:
if (!_subtitles) _subtitles = [NSMutableArray new];
[_subtitles insertObject:self.label.text atIndex:0];
This line:
if (!_subtitles) _subtitles = [NSMutableArray new];
Is just to make sure that our _subtitles dictionary exists, and if it does, we make sure that it isn't overwritten. the [NSMutableArray new] syntax is something that I personally like because it looks clean; however, many prefer [[NSMutableArray alloc]init]. Just so you're aware.
I am new in iOS development. Now I want to give an external property(similar to tag) to a UIButton. Is it is possible? If it is possible ,how to do this?
If any body know, please help me.
You can use a NSArray, and the index of the array is the UIButton's tag.
You can either create a UIButton subclass, or use Obj-C runtime associations like this
#import <objc/runtime.h>
static char kMyExtendedPropKey;
objc_setAssociatedObject(myButton,
&kMyExtendedPropKey,
yourObjectToAssociate,
OBJC_ASSOCIATION_RETAIN);
Note that associations can be used in conjunction with categories to add new properties to existing classes! But use with caution, subclassing is the preferred way.
Subclass UIButton, assuming you want an NSString in your button:
.h
#interface MyAttributedButton : UIButton {
NSString *myExternalProperty;
}
#property(nonatomic, retain) NSString *myExternalProperty;
#end
.m
#implementation MyAttributedButton
#synthesize myExternalProperty;
#end
I have an iPad app in progess but I'm having difficulty catching the selection of a row in my table view. I know this is because I haven't defined my delegate properly yet but, after 2 hours on the net, it still isn't making much sense.
What I'm trying to do is pass the selected table row item to a new view that displays info based on the selection - pretty standard.
I set up the tableViewController sub class using the option to create it as a UITableViewController subclass which, unless I am wrong, incorporates the delegates (UITableViewDelegate and UITableViewDataSource) automatically.
In the didSelectRowsAtIndex method I'm trying to create a DetailViewController. I've tried with a nib file and creating one purely in code but the class is never created. I'm missing a step I'm sure of it but I can't find what it is. At some point shouldn't I be defining what function I want to access with the selected row? But where? How?
In what I considered was my best attempt, I created the DetailViewController, set a string variable in the detailViewController to the selected row, and then tried to add the detailViewController view to display. I figured I could then use the viewDidload to call the next function but the view never got displayed on screen.
Some basic guidence would be nice. Or a decent tutorial would be nice. No calls to read the relevant docs please, I've been over it and right now I need a example to pull things together.
Thanks,
Steve
I think you are missing this line in your didSelectRowAtIndexPath: method
[self presentModalViewController:controller animated:YES];
where controller is an object of class DetailViewController
Yeah, maybe paste the code snippet will be easier to figure out what's going on here. And are those delegate(didSelectRowAtIndexPath:) methods being called correctly?
Try this,
this goes in didSelectRowAtIndexPath
MoreInfoTable *moreInfoView = [[MoreInfoTable alloc] initWithStyle:UITableViewStyleGrouped];
//in the MoreInfoTable, make properties like titles etc.
[self.navigationController pushViewController:moreInfoView animated:YES];
[moreInfoView release];
}
here's an example of an MoreInfoTable.h
#interface MoreInfoTable : UITableViewController {
NSMutableArray *moreInfo;
NSURL *getDirections;
NSURL *getWebsite;
NSMutableString *getPhoneNumber;
NSString *address;
NSString *footer;
float lat, lon;
}
-(void)goToWebsite;
-(void)goToMaps;
-(IBAction)addToFavorites:(id)sender;
-(void) callNumber;
#property (nonatomic,retain) NSURL *getDirections;
#property (nonatomic,retain) NSURL *getWebsite;
#property (nonatomic,retain) NSMutableString *getPhoneNumber;
#property (nonatomic,retain) NSString *footer;
#property (nonatomic,retain) NSString *address;
#property (readwrite) float lat;
#property (readwrite) float lon;
#end
now back in the other file in which you declare the table, you can say
MoreInfoTable *moreInfoView = [[MoreInfoTable alloc] initWithStyle:UITableViewStyleGrouped];
//in the MoreInfoTable, make properties like titles etc.
moreInfoView.title = #"TITLE!";
//etc.
[self.navigationController pushViewController:moreInfoView animated:YES];
[moreInfoView release]; //
I'm new to Obj-C and iPhone SDK. The test application I'm stock with is a color switcher containing two buttons ("Back", "Forward") and one text label. The idea is to switch between rainbow colors (background) and setting an appropriate text label in a cyclic manner.
I declared NSArray (which is to contain colors names) in RainbowViewController.h, synthesized it in RainbowViewController.h and I can't add any string into that array.
This is "h" file:
#import <UIKit/UIKit.h>
#interface RainbowViewController : UIViewController {
IBOutlet UILabel *currentColorTextLabel;
NSArray *colorsArray;
NSString *msg;
}
#property (nonatomic, retain) IBOutlet UILabel *currentColorTextLabel;
#property (nonatomic, retain) NSArray *colorsArray;
#property (nonatomic, retain) NSString *msg;
- (IBAction) pressForwardButton;
- (IBAction) pressBackButton;
#end
This is "m" file:
#import "RainbowViewController.h"
#import <Foundation/Foundation.h>
#implementation RainbowViewController
#synthesize currentColorTextLabel;
#synthesize colorsArray;
#synthesize msg;
int currentArrayIndex = 0;
colorsArray = [[NSArray alloc] init]; //here i get "Initializer element is not constant" error message
[coloursArray addObject:#"Red"]; //here I get "Expected identifier or '(' before '[' token"
[coloursArray addObject:#"Orange"];
//etc
- (IBAction) pressForwardButton {
//here I'm going to increment currentArrayIndex, set an appropriate color, and update a currentColorTextLabel based on currentArrayIndex.
}
- (IBAction) pressBackButton {
}
//auto-genereted code here
#end
I'm new to obj-c as well, but I think you need to initialize the array with objects, or use an NSMutableArray if you want to add objects after it is created.
You have the code that should go in your init method just sitting out in the middle of the file. You can't set instance variables like that.
jasongetsdown is correct. You need to instantiate the NSArray object with the objects it will contain and nil terminated.
#"Red", #"Blue", nil
If you wish to have an array that you can change you need to make it a Mutable Array.
However, you have another problem here. Your property that you are synthesizing and allocating for is an object named colorsArray and you are trying to pass a method to a coloursArray object, two different spellings.