I'm going to have objects, read from a .csv (Comma seperated file) which contains file names, later. Thats why i'm trying to do it like this.
What I would like to accomplish is to have the button get the image from the filename in the csv.
What i've tried so far:
The Object:
#interface question : NSObject
{
#private
UIImage *imageName;
}
#property (nonatomic, retain)UIImage *imageName;
(I have tried with NSString aswell as UIImage, neither works like I want them)
ViewController:
- (void)viewDidLoad
{
[super viewDidLoad];
question *question1 = [[question alloc]init];
[question1.imageName initWithContentsOfFile:#"Default.png"];//Will be read from a csv later on, just typing it in manually for a test
testImage = question1.imageName;
}
-(void)imageshow
{
//(UIImage *)testImage;(NSString *)imageNameString; Didnt work
//[self.testImage initWithContentsOfFile:#"%#",questiont.imageName]; - Doesnt work either
[testButton setImage:testImage forState:UIControlStateNormal];
}
-(IBAction)test:(id)sender
{
[self imageshow];
}
Where this code fails is when I press the test button, nothing happens (not crash)
How can I do this properly?
(Add an image with a text filename to a NSObject and then show it in a button/image view)
question1.img = [UIImage imageNamed:#"Default.png"];
[testButton setImage:question1.img forState:UIControlStateNormal];
and yes you can try the following for dynamic images
question1.img = [UIImage imageNamed:[NSString stringWithFormat:"%#",imgName]];
imgName => is the name of the image not the image
example: "abc.png" or "123.png" ,etc
if your property is named imageName the accessor variable is automaticly named _imageName.
You are using two different variables in your code.
#interface question : NSObject
{
#private
UIImage *_imageName;
}
#property (nonatomic, retain)UIImage *imageName;
imageName is not a great name for an property that contains an image.. it would better fit to a string.
There are some things to change.
For mere conventional reasons write all class names with an upper case at the beginning. It eases reading, exchange in forums as SO and avoids mistakes.
Second name variables either speaking or abstract, preferrably speaking. But to not choose a mislieading name such imageName. There should be a name in that variable, not an image, or maybe the graphic that displays a name. :)
imageWithContentsOfFile expects a fully qualified file name. If "Default.png" is part of your boundle, as I guess by its name, then imageNamed:#"Default.png" would do.
Your setImage looks nearly good. It cannot work of course while your image is (null). However, it is not good business practis accessing the iVar direct at this point. You shoudl use its setter/getter. Use instead:
[self.testButton setImage:self.testImage forState:UIControlStateNormal];
In your case it does not make much of a difference. But similar to the other conventions it helps avoiding errors when ever you mix your code with some code that you found on the web or when you work in a team.
Related
I have created a UIImage subclass named MyImage.
MyImage obviously responds to every method originally implemented by UIImage. I would like to completely hide UIImage implementation, so for example MyImage redeclares a method like:
- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets;
to
- (MyImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets;
I attempt to write the implementation like:
- (MyImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets {
UIImage *original = [super resizableImageWithCapInsets:capInsets];
MyImage *result = [[[self class] alloc] initWithUIImage:original];
return result;
}
- (id) initWithUIImage:(UIImage *)image {
// HOW TO IMPLEMENT THIS METHOD???
}
but I stopped at initWithUIImage method. How can I achieve such a behavior without using composition?
You don't want to do that. Its a lot of unnecessary code with a high risk of breaking something. Don't redeclare these methods. Is there a specific reason that you want to do that?
The problem here is simple and it is called: INHARITANCE.
Do not do inaritance but provide some class which owns UIImage. It will be easier and more relialeble.
Another issue is that you didn't expain why you need change something in UIImage! I'm prety sure yuo are trying to resolve some simple problem in nasty way.
The answer is that you cannot do what it seems like you're attempting to do. MyImage IS a UIImage, meaning it implicitly has all methods and properties of UIImage. You can add new ones, but never remove existing ones.
And UIImage is used all over the system APIs. What exactly are you attempting to accomplish by doing this?
I am using following for comparing button's background image.
if([[button currentBackgroundImage] isEqual:[UIImage imageNamed:#"image1.png"]]){
// do something
}
The code works fine when application is in active state. But when app gets back from idle state the above code doesn't work.
Any idea why this happens?
Thanks
The images don't compare after you come back from background because you're creating a new instance of that image for your comparison by using [UIImage imageNamed:#"image1.png"] (the images are compared by looking at their hash values, not by looking at the actual image contents). If you create a property for your image, when you first use imageNamed:, and use that in the comparison, it should work properly. So, I tested with this code, and it returned true when I checked after coming back from the background (I set the button's background image in IB).
#interface ViewController ()
#property (weak, nonatomic) IBOutlet UIButton *greenButton;
#property (strong,nonatomic) UIImage *greenPng;
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.greenPng = [UIImage imageNamed:#"Green.png"];
}
- (IBAction)checkImages:(id)sender {
BOOL isTheSame = [self.greenButton.currentBackgroundImage isEqual:self.greenPng];
NSLog(#"The images are %#",isTheSame? #"the same" : #"different");
NSLog(#" button image hash is %d",self.greenButton.currentBackgroundImage.hash);
NSLog(#" imageNamed image hash is %d",self.greenPng.hash);
}
After Edit: I'm not sure my explanation is quite correct -- in one run of the app, you can make multiple calls to imageNamed:, and all the images that are returned will have the same hash (including the image you pick in IB, if you do it that way). I think this is due to cashing. In any case, when you come back from the background and call imageNamed: again, it returns an image with a different hash.
OK I have a specific situation. I am using a custom class to create some buttons and I can set their tag property with unique numbers like:
button.tag =[NSNumber numberWithInt:[10]];
This is very useful in another part of my program because I can access this unique tag like:
UIButton *clicked= (UIButton *) sender;
ButtonTag = [NSString stringWithFormat:#"%d", clicked.tag];
Now I want to pass one more unique property just like this. I am making this up but this is how I envision it
button.tagCREATED_BY_ME =[NSNumber numberWithInt:[9000]];
The question might be poorly worded but I don't know any better so I called it "tag".(correct wording might be element/property etc) How do I create a similar property to function just like .tag?
Thanks a lot!
arda
What do you want to achieve?
There is the possibility of adding an associative references. The good part about this, is that you don't need to sub-class it. So, start by creating a Category for the UIButton:
#interface UIButton (ExtraTag)
#property (nonatomic, retain) id extraTag;
#end
And the .m:
static char const * const ExtraTagKey = "ExtraTag";
#implementation UIButton (ExtraTag)
#dynamic extraTag;
- (id)extraTag {
return objc_getAssociatedObject(self, ExtraTagKey);
}
- (void)setExtraTag:(id)newExtraTag {
objc_setAssociatedObject(self, ExtraTagKey, newExtraTag, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
You can check the article I used.
CALayer allows Key-Value coding actually.
You can literally just do this (on any UI object):
[button.layer setValue:#(9000) forKey:#"tagCREATED_BY_ME"];
and to read it just use
[button.layer valueForKey:#"tagCREATED_BY_ME"]
Obligatory, the above is all you need to get this up and going, you're good to go.
For others, more advanced /or/ specific stuff follows:
If you need these keys to have a default value when nothing has yet been assigned to them... You can set these custom "tags" (eh) to have default return values if you name them according to a pattern. For example I start all of my layer keys name's with "customKey_". So the above would have been #"customKey_tagCREATED_BY_ME", then you can have your .m file return the default key values for any standard key like masksToBounds but then return a very specific value for your keys (aka keys that start with "customKey_") with the following method:
+(id)defaultValueForKey:(NSString *)key {
if ([key hasPrefix:#"customKey_"]) {
return #(0);
}
return [CALayer defaultValueForKey:key];
}
The reason you have to have a naming pattern (like always having the prefix "customKey_") is so you don't interfere with a CALayer's natural properties like .size and .backgroundColor, etc. Your default value you want returned will only be returned on properties (key) starting with "customKey_" or whatever naming pattern you use.
In your subclassed/custom button, you can add a string property or even an integer property whichever you feel good.
#interface CustomButton: ....
...
#property(strong) NSString *createdBy;
#end
Then you can access those as aButton.createdBy
You can also use Associated references instead of tags manipulation
#import <objc/runtime.h>
static char kThumbnailButtonAssociatedPhotoKey;
// ...
- (void)setAssociatedPhoto:(Photo *)associatedPhoto
forThumbnailButton:(UIButton *)thumbnailButton
{
objc_setAssociatedObject(thumbnailButton,
&kThumbnailButtonAssociatedPhotoKey,
associatedPhoto,
OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (Photo *)associatedPhotoForThumbnailButton:(UIButton *)thumbnailButton
{
return objc_getAssociatedObject(thumbnailButton,
&kThumbnailButtonAssociatedPhotoKey);
}
Now we can easily set/get the associated photo for a button:
- (void)configureThumbnailButtonForPhoto:(Photo *)photo
{
// ...
[self setAssociatedPhoto:photo
forThumbnailButton:thumbnailButton];
// ...
}
- (void)thumbnailButtonTapped
{
Photo *photo = [self associatedPhotoForThumbnailButton:thumbnailButton];
// ...
}
Blog post about tags and associated references
You can subclass UIButton.
In your subclass, add a new property:
#property (strong, nonatomic) NSNumber *tagCREATED_BY_ME;
You could look into KVC.
Or if you wanted to stick to the KISS principle - subclass UIButton and create a property.
Im trying to make it so that every single UIControl in my application (UIButton, UISlider, etc) all have special extra properties that I add to them.
I tried to accomplish this by creating a UIControl Category and importing it where needed but I have issues.
Here is my code.
My setSpecialproperty method gets called but it seems to be getting called in an infinite loop until the app crashes.
Can you tell me what Im doing wrong or suggest a smarter way to add a property to all of my UIControls?
#interface UIControl (MyControl)
{
}
#property(nonatomic,strong) MySpecialProperty *specialproperty;
-(void)setSpecialproperty:(MySpecialProperty*)param;
#end
////////
#import "UIControl+MyControl.h"
#implementation UIControl (MyControl)
-(void)setSpecialproperty:(MySpecialProperty*)param
{
self.specialproperty=param;
}
///////////////
#import "UIControl+MyControl.h"
#implementation ViewController
UIButton *abutton=[UIButton buttonWithType:UIButtonTypeCustom];
MySpecialProperty *prop=[MySpecialProperty alloc]init];
[abutton setSpecialproperty:prop];
While you can't add an iVar to UIControl via a category, you can add Associated Objects, which can be used to perform much the same function.
So, create a category on UIControl like this:
static char kControlNameKey;
- (void) setControlName: (NSString *) name
{
objc_setAssociatedObject(self, &kControlNameKey, name, OBJC_ASSOCIATION_COPY);
}
- (NSString *) controlName
{
return (NSString *)objc_getAssociatedObject(array, &kControlNameKey);
}
There's more to it than that, I guess you'll need to check if an association exists before setting a new one, otherwise it will leak, but this should give you a start.
See the Apple Docs for more details
self.specialproperty=param is exactly the same as calling [self setSpecialproperty] (see here for some totally non biased coverage of Obj-C dot notation), which makes your current usage infinitely recursive.
What you actually want to do is:
-(void)setSpecialproperty:(MySpecialProperty*)param
{
_specialproperty = param;
}
Where _specialproperty is the implicitly created ivar for your property.
I'm assuming there's some reason why you've implemented your setSpecialproperty setter? Why not just use the one that is implicitly created for you?
the problem is that you can not add a property to a category, you can add behavior (methods) but not properties or attributes, this can only be done to extensions, and you can not create extensions of the SDK classes
use your method as
change your method name to
-(void)setSpecialproperty:(MySpecialProperty *)specialproperty
-(void)setSpecialproperty:(MySpecialProperty*)specialproperty
{
if(_specialproperty!=specialproperty)
_specialproperty = specialproperty;
}
and synthesize your specialProperty as
#synthesize specialproperty=_specialproperty;
I need to get the value of a UIImage's image as a string.
Previously I was doing:
if(images[imageNo].image == [UIImage imageNamed:#"image1.png"])
{
But now I have a lot more conditions so I would like to use a switch, doing:
switch(images[imageNo].image)
{
case #"image1.png":
break;
}
Is there a way to achieve this? Thanks!
Mmm I am not sure what you want to accomplish here but using [UIImage imageNamed:#"image1.png"], is definitely a very bad way to do the comparison as you are creating a new UIImage object on the fly for no reason at all, furthermore you are using the == operator when you should be using isEqual since they are objects.
I believe what you want to do is convert it to a base 64 string perhaps?. If so you an use this:
NSData *imageData = UIImageJPEGRepresentation(myImage, 1.0);
NSString *encodedString = [imageData base64Encoding];
The answer provided by H2C03 is appropriate. Use a dictionary to associate the names.
However, an alternative is using associative objects. Note that there is a cost in both space and time using associative objects, but they are convenient for just this type of case (adding a category-property).
#interface UIImage (MyImageLabel)
#property (nonatomic, copy) NSString *label;
#end
#import <objc/runtime.h>
#implementation UIImage (MyImageLabel)
static char const kImageLabelKey[1];
- (NSString*)label {
return objc_getAssociatedObject(self, kImageLabelKey);
}
- (void)setLabel:(NSString *)label {
objc_setAssociatedObject(self, kImageLabelKey, label, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
#end
Now, you can have a label property on your UIImage instances, like so:
myImage.label = someLabelStringCouldEvenBeFilename;
and
if ([myImage.label isEqualToString:someString]) {
}
The typical caveats apply regarding anything in a category. Most will encourage you to use a unique prefix or postfix to differentiate your category methods from potential future Apple names.
Note, that you could add another method to the category, like this...
+ (UIImage)myImageNamed:(NSString*)name {
id result = [self imageNamed:name];
[result setLabel:name];
return result;
}
and now you automatically set the label.
Of course, you could do this as a subclass, if you will always be creating your own image, and avoid the "nastiness" associated with associative objects (though all your images need to be MyUIImages).
#interface MyUIImage : UIImage
#property (nonatomic, copy) NSString *label;
#end
#implementation MyUIImage
// Now, you override imageNamed:
+ (UIImage*)imageNamed:(NSString*)name {
UIImage *image = [super imageNamed:name];
self.label = name;
return image;
}
#end
Both of your approaches are incorrect. The first one relies on caching (which is not documented), meanwhile the second is a syntax error - the 'case' keywords expect a compile-time constant expression.
As far as I know, there's no such a method in the iOS SDK that would return an image's filename - simply because it's not a property of the image (what would it return for a programmatically created image?). You should instead try to operate on an NSDictionary, storing the UIImage objects associated with the filenames as keys, and comparing the keys using isEqualToString:.
So you should create your images only once, and store them in a dictionary:
// assuming `images` is an already created instance variable of your class
[images setObject:[UIImage imageNamed:#"ImgOne.png"] forKey:#"ImgOne.png"];
// and so on, with every image you need
// then once you have to check against a file name, use:
UIImage *img = [images objectForKey:#"FileName.png"];
if ([someImage isEqual:img]) {
// you can now be sure that the image set to the object was once named "FileName"
}