Initialising a category in objective-c - ios

I'm writing a category for UITextField to include validation. I wish to change the text field's visual according to validation state (such as having an approved icon as its right view). For this, I keep a validation state property and wish to update the visual on its setter.
Here's what I have (UITextField+Validation.h)
#interface UITextField (Validation)
// Validator registration
- (void)addValidator:(id<HyValidator>)validator;
// Validation
- (void)validate;
#end
UITextField+Validation.m
#interface UITextField (Validation_Private)
#property (nonatomic, strong) NSMutableArray * validators;
#property (nonatomic) HyValidationState validationState;
#end
#implementation UITextField (Validation_Private)
- (NSMutableArray*)validators
{
if (self.validators == nil) {
self.validators = [[NSMutableArray alloc] init];
}
return self.validators;
}
- (void)setValidators:(NSMutableArray *)validators
{
self.validators = validators;
}
- (HyValidationState)validationState
{
}
- (void)setValidationState:(HyValidationState)validationState
{
}
- (void)addValidator:(id<HyValidator>)validator
{
[[self validators] addObject:validator];
}
- (void)validate
{
}
#end
The question is: how do I initialise validators and validationState?

Don't use categories for this. Subclass instead. Or, better yet, use the UITextField's delegate to do the validation, as intended.
Using categories to extend the behavior of existing system classes is generally considered to be bad design.
By using delegation, you can decouple input validation from a specific input class and, thus, your validation can be easily re-used across other input mechanisms.

You want to add a storage to your class UITextField (simple ivar to hold the data). Since you don't have the code you can't extend the class. However in objective C you can achieve this using associated reference. ObjC Runtime comes handy helping you to attach a storage to your class and make you interact with the storage as if it was built in within the class.
An example of how to achieve this is found in Ole Begemann blog here http://oleb.net/blog/2011/05/faking-ivars-in-objc-categories-with-associative-references/

Related

Setters, Getters and Exposing real core data types, how do I do that?

I have a core data entity that has a structure like this:
number (integer 16),
reference (binary)
image (binary)
I have created a class for that entity.
The header of that class has these declarations for the entity property.
#property (nonatomic, retain) NSNumber * number;
#property (nonatomic, retain) NSData * reference;
#property (nonatomic, retain) NSData * image;
but in fact, these 3 properties are
number = NSInteger
reference = NSArray
image = UIImage
because I cannot store arrays and images on core data directly, I have to convert it to NSData to save but I don't care for the property being declared as NSData, because the conversion to and from NSData is something internal to the entity and should not be exposed to code outside the class.
I want these header properties to be declared like
#property (nonatomic, assign) NSInteger number;
#property (nonatomic, retain) NSArray * reference;
#property (nonatomic, retain) UIImage * image;
and I want to, for example, when I assign an array to reference that is converted to NSData internally.
I know I have to create setters and getters to do that but my problem is that the entity is already using these names. Obviously I can rename all core data entities to have a prefix like xnumber, xreference, ximage, etc., so I will have no collisions between the names/types I want to expose and those I want to hide internally.
Is there any other alternative to that? My fear is ending with a sea of references that are similarly.
What you did in your application is probably most common fail using core data. By no means you should be encouraged to use the core data classes directly as you did, do always use subclassing, categories or (best of all) use wrappers.
Since in most cases when you edit an entity in your model you wish to delete the auto generated file(s) and create new ones those files should be unmodified. This is the main reason I discourage you to use any quick fixes such as modifying the names in your model and then creating the custom setters.
Why I suggest the wrappers most is because you can build your own interface with it. You can create exactly as many methods, accessories as you need on it, you can use data protection such as having read-only parameters... So when you modify the data model there should be no difference in the application at all, when you will possibly add some extra tables for some optimisations or some internal functionality you will have no issues hiding those accessories. Other then that having an extra layer will make it very easy for you to create some caching, easy debugging since you can put a breakpoint or log to more or less any and every accessory, you can internally maintain multithreading operations...
I can understand at this point migrating your code to some other system might take a bit long but that is something you should consider. If the application is anything but almost done I suggest you do migrate it: If you create a wrapper with same properties as are already used in the application it is possible to simply change the class names where it was already used, this shouldn't take too long. If you choose to continue working as it is you will most likely encounter some much harder issues and if nothing else remember this when you will start a new application.
Edit: Wrapper explanation and example
By wrapper I mean a class instance that holds another instance and builds an interface around it. Let me show you a nice example first:
Interface:
#interface EntityWrapper : NSObject
#property NSInteger number;
#property UIImage *image;
+ (NSArray *)fetchAll;
+ (void)invalidateCache;
#end
Implementation:
#class EntityName;
static NSArray *__entityCache = nil;
#interface EntityWrapper() {
EntityName *_boundEntity;
}
#end
#implementation EntityWrapper
- (instancetype)initWithEntity:(EntityName *)entity {
if((self = [super init])) {
_boundEntity = entity;
}
return self;
}
+ (NSArray *)fetchAll {
if(__entityCache == nil) {
NSMutableArray *toReturn = [[NSMutableArray alloc] init];
NSArray *entityArray = nil; //fetch from data base
for(EntityName *entity in entityArray)
[toReturn addObject:[[EntityWrapper alloc] initWithEntity:entity]];
__entityCache = [toReturn copy];
}
return __entityCache;
}
+ (void)invalidateCache {
__entityCache = nil;
}
- (void)setNumber:(NSInteger)number {
_boundEntity.number = #(number);
}
- (NSInteger)number {
return [_boundEntity.number integerValue];
}
- (void)setImage:(UIImage *)image {
_boundEntity.image = UIImagePNGRepresentation(image);
}
- (UIImage *)image {
return [[UIImage alloc] initWithData:_boundEntity.image];
}
#end
As you can see here I am building an interface around the entity using custom setters and getters. I even create a method to fetch all objects from the data base, next step might be to fetch them with some predicate or in this case rather some custom options. I also added a most simple cache just to see the concept.
The number is now a NSInteger instead of a NSNumber which can be quite a convenience but be careful doing this as you might need to know if number is nil. For this case you could also create another property such as BOOL numberIsSet.
Pretty much the same goes for the image. You need no transformers at all, just a getter and a setter (which is pretty much the same with transformers but this approach is much more dynamic).
So creating the wrapper kind of gives you the ultimate power. The idea is to create as small interface as possible and as simple as possible. That means there are just as many methods in the header file as needed, rest is hidden. The logic behind these methods can be extremely complicated but will still be maintainable since it is a closed system (does not depend on nothing but the entity), to give you an example:
Interface:
#property (readonly) NSDecimalNumber *heavyValue;
Implementation:
- (NSDecimalNumber *)heavyValue {
NSDecimalNumber *valueA = _boundEntity.valueA;
NSDecimalNumber *valueB = _boundEntity.valueB;
NSDecimalNumber *valueC = _boundEntity.valueC;
return [[valueA decimalNumberByAdding:valueB] decimalNumberByDividingBy:valueC];
}
Now this is quite a standard procedure and will work great but this method can be quite heavy on the CPU. If this method is called a lot you might get to a point where you want to optimise by storing the result into the entity itself. So all you do is add another value into the model heavyValue and the code:
- (NSDecimalNumber *)heavyValue {
NSDecimalNumber *toReturn = _boundEntity.heavyValue;
if(toReturn == nil) {
NSDecimalNumber *valueA = _boundEntity.valueA;
NSDecimalNumber *valueB = _boundEntity.valueB;
NSDecimalNumber *valueC = _boundEntity.valueC;
toReturn = [[valueA decimalNumberByAdding:valueB] decimalNumberByDividingBy:valueC];
_boundEntity.heavyValue = toReturn;
}
return toReturn;
}
- (void)setValueA:(NSDecimalNumber *)valueA {
_boundEntity.valueA = valueA;
_boundEntity.heavyValue = nil; //this invalidates the value
}
So that is quite an extreme change in logic behind a simple getter but the rest of your code is unharmed, it still all works as it should.

Changing label color of a label in a different view (delegates?) [Spritebuilder]

I have two scenes that I made in SpriteBuilder, one is Shop and the other is UpgradesNew. Shop is a CCNode layer and UpgradesNew is a CCNode layer. I have two CCScrollViews in the MainScene that load Shop and UpgradesNew respectively.
When one button in Shop is tapped, the label in UpgradesNew should change colors. I have been trying to implement this using delegates but it's not working.
Here's what I did...
In shop.h I set the protocol:
#protocol changeColorProtocol <NSObject>
#required
-(void)changeColor;
#end
Then I set the id
#property (nonatomic, retain) id <changeColorProtocol> delegate;
Here is the button that when clicked, should use changeColor. This is in shop.m
-(void) buyDiggerShibe {
[self.delegate changeColor];
[self didLoadFromCCB];
}
Now in UpgradesNew.h I made it adopt the protocol like this
#interface UpgradesNew : CCNode <changeColorProtocol>
And in UpgradesNew.m
I set delegate to self in ViewDidLoad.
Shop *shop = [[Shop alloc]init];
shop.delegate = self;
.
-(void)changeColor {
if (hasDigger == YES) {
shovelRequires.color = [CCColor greenColor];
NSLog(#"HEY HEY HEY");
}
}
I probably have parts of the delegate placed in the wrong area because I was trying to switch them around when it wasn't working, I'm not sure where they are supposed to go. I've watched multiple delegate tutorials and it just seems overly complicated, at least with what I am trying to do.
Any ideas?
EDIT:
Tried this.
I created a property in UpgradesNew
#property (strong, nonatomic) Shop *shop;
Then I synthesized it in the implementation and allocated it like this in didLoadFromCCB, instead of creating a new object:
self.shop = [[Shop alloc]init];
shop.delegate = self;
EDIT: This is how I am creating objects.
Drag a label into a layer. Identify it then define it in header as CCLabelTTF *label; That's it, thats all I do to create any object on the layer.
To create a layer like Shop or UpgradesNew, I hit New -> File -> Layer. That creates a new CCNode. Then I set the class of the CCNode, as shown in the picture the CCNode that is highlighted has a class of MainScene. If I want to establish a #property to that CCNode I just type the name in the box right below custom class and set it as doc root var, and then put it in the header as CCNode *MainScene. I don't do anything other than that.
I don't know anything about SpriteBuilder, so it's a bit hard to address your question. You might want to add SpriteBuilder to the title of your post so people who use that framework are likely to read it.
You need to explain how the 2 "CCNode layer"s are created, and how you link them together. In order for one object to have another object as a delegate, the delegate property has to be set somewhere. Where is that setup being done? Have you set a breakpoint at the line
[self.delegate changeColor];
To make sure that self.delegate is not nil?
Have you set a breakpoint in your changeColor method, or added a log statement, to see if it's being called? My guess is that self.delegate is nil, so the messages is being dropped on the floor (it's legal to send messages to nil in Objective-C. It just doesn't do anything.)

Problems with <UITextinputDelegate> protocol implementation

What I am trying to implement is a UITextField that sees words as characters. Specifically, im trying to see the mathemathical expression sin( as one character for example. I thought to solve this problem by implementing my own UITextInputDelegate. However, the four required functions from this protocol never get called when I implement or adopt this protocol. I tried implementing it in the following ways:
By subclassing a UITextField.
#interface BIDUItextFieldDelegate : UITextField < UITextInputDelegate >
By subclassing a NSObject.
#interface BIDTextfieldInputDelegate : NSObject < UITextInputDelegate >
The corresponding .m file contains:
#implementation BIDTextfieldInputDelegate
- (void)selectionWillChange:(id <UITextInput>)textInput
{
NSLog(#"sWill");
}
- (void)selectionDidChange:(id <UITextInput>)textInput
{
NSLog(#"sDid");
}
- (void)textWillChange:(id <UITextInput>)textInput
{
NSLog(#"tWill");
}
- (void)textDidChange:(id <UITextInput>)textInput
{
NSLog(#"tDid");
}
For example for the second approach (via subclassing NSObject), I do the following in the (id) init method in an additional custom UITextfield class which is displayed within the app:
//textInputDel is an instance of the custom NSObject class that adopts the above UITextInputDelegate protocol
self.textInputDel = [[BIDTextfieldInputDelegate alloc] init];
self.inputDelegate = self.textFieldDel;
Does anyone know what I am doing wrong, or has a better solution?
UITextInputDelegate is not a protocol that you implement; rather, the system creates an object conforming to UITextInputDelegate, and assigns it as the .inputDelegate of a First Responder that conforms to UITextInput.
The methods of UITextInputDelegate are methods for your UITextInput-conforming responder to call on your .inputDelegate to inform it that you have changed your text or selection via means other than keyboard input.

Passing multiple tags with UIButton

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.

Adding a property to all of my UIControls

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;

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