I'm relatively new to ARC. I'm making an UIView subclass, that will have two labels (title and subtitle). I don't want to publicly expose the labels as properties, only their text.
I'm currently using this:
#interface MyView : UIView
#property (nonatomic, strong) NSString *title;
#property (nonatomic, strong) NSString *subtitle;
#end
#implementation MyView
{
UILabel *_titleLabel;
UILabel *_subtitleLabel;
}
- (void)setTitle:(NSString *)title
{
[_titleLabel setText:title];
}
- (NSString *)title
{
return [_titleLabel text];
}
- (void)setSubtitle:(NSString *)subtitle
{
[_subtitleLabel setText:title];
}
- (NSString *)subtitle
{
return [_subtitleLabel text];
}
#end
Are my two #properties correctly declared? Should I use the strong, weak or any other qualifier? And why?
If you are going to work with setter / getter, I think the appropiate tag would be the readwrite. strong weak retain etc apply when the property is the setter/getter for an instance variable.
Related
I have good Setter and Getter code for Object. How do same for BOOL using objc/runtime.h like here?
objc_getAssociatedObject require object
.h
#import <Foundation/Foundation.h>
#interface UITableView (Additions)
#property (nonatomic, retain) NSNumber *allowReplenishment;
#end
.m
#import "UITableView+Additions.h"
#import <objc/runtime.h>
#implementation UITableView (Additions)
- (NSNumber *)allowReplenishment {
return objc_getAssociatedObject(self, #selector(allowReplenishment));
}
- (void)setAllowReplenishment:(NSNumber *)value {
objc_setAssociatedObject(self, #selector(allowReplenishment), value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
#end
If you want to declare your bool property
#property (nonatomic, assign) BOOL isAllowReplenishment, just create the object in the setter instead, as needed:
- (void)setIsAllowReplenishment:(BOOL)isAllowReplenishment
{
NSNumber *isBool = [NSNumber numberWithBool:isAllowReplenishment];
objc_setAssociatedObject(self, #selector(isAllowReplenishment), isBool, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (BOOL)isAllowReplenishment
{
NSNumber *isBool = objc_getAssociatedObject(self, #selector(isAllowReplenishment));
return isBool.boolValue;
}
I have a class(Core Data Generated):
#interface Place : NSManagedObject
#property (nonatomic, retain) NSString * title;
#property (nonatomic, retain) NSString * subtitle;
#property (nonatomic, retain) NSNumber * latitude;
#property (nonatomic, retain) NSNumber * longitude;
#end
#implementation Place
#dynamic title;
#dynamic subtitle;
#dynamic latitude;
#dynamic longitude;
#end
Adn a category for it:
#interface Place (Create)
+ (Place *)placeWithTitle:(NSString *)title
inManagedObjectContext:(NSManagedObjectContext *)context;
+(Place *) placeWithTitle:(NSString *)title andSubtitle:(NSString *)subtitle inManagedObjectContext:(NSManagedObjectContext *)context;
+(Place *) placeWithCoordinate:(CLLocationCoordinate2D) coordinate inManagedObjectContext:(NSManagedObjectContext *)context;
- (void) setLattitudeAndLongitudeByCoordinate:(CLLocationCoordinate2D) coordinate;
- (CLLocationCoordinate2D) coordinate;
#end
In this category a have to instance methods:
- (void) setLattitudeAndLongitudeByCoordinate:(CLLocationCoordinate2D) coordinate
{
self.latitude=[NSNumber numberWithDouble:coordinate.latitude];//break point HERE
self.longitude=[NSNumber numberWithDouble:coordinate.longitude];
}
-(CLLocationCoordinate2D) coordinate
{
CLLocationCoordinate2D coord;//break point HERE
coord.latitude=[self.latitude doubleValue];
coord.longitude=[self.longitude doubleValue];
return coord;
}
As you see i have to breakpoints there. Now, then i call those methods
#import "Place+Create.h"
-(void)someMethod
{
[self.place setLattitudeAndLongitudeByCoordinate:coordiante];
}
It never seem to reach those breakpoints inside the method setLattitudeAndLogitudeByCoordinate,
and debug shows that it even doesn't call them! Why?
Is someMethod ever reached? Check that using a breakpoint or an extra NSLog at its head.
If not, then your problem is somewhere else as your program flow is different than you expected it to be.
If it is reached then self.place obviously is nil. That means you never initialized it and again, your program flow is different than you thought it would be.
I have a subclass of UITableViewController, and I init the subclass with a NSMutableArray of another custom class:
#import <UIKit/UIKit.h>
#import "NUBCheckpointModel.h"
#interface NUBUserCheckpointModel : NSObject
#property (nonatomic,assign) NSString* objId;
#property (nonatomic,assign) NSString* userId;
#property (nonatomic,assign) NSString* checkpointId;
#property (nonatomic,assign) NSDate* dateAdded;
#property (nonatomic,assign) NUBCheckpointModel* checkpoint;
+ (NUBUserCheckpointModel*) fromJson: (NSString*)json;
#end
This array that is generated from another ViewController, gets passed into this subclassed TableViewController, of which contain this property
#property (nonatomic,retain) NSMutableArray* userCheckpointData;
This property is set like this:
- (id)initWithFrame: (CGRect)frame withType: (TableType)typeOfTable fromParent: (UIViewController*)parent data: (NSMutableArray*)ucpData
{
self = [self init];
if (self) {
self.tableView = [[UITableView alloc] initWithFrame:frame];
self.parentController = parent;
self.userCheckpointData = ucpData;
[self styleTable];
[self addPullToRefreshHeader];
typeCategory = typeOfTable;
}
return self;
}
All is fine up to this part, and any manipulation including trying to get an object from the array works fine. I tested it.
The code I used to test the array is:
NUBUserCheckpointModel* model = [self.userCheckpointData objectAtIndex:0];
NSLog(model.objId);
However, this very same code, when used here:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
Gives me exc_bad_access. May I know why this happens? I can't seem to figure out why. I'm using ARC btw. Thank you.
While adding the property, you need to take care of the memory management. For string, it is not good practice to set assign property.
Instead , do as following,
#property (nonatomic,copy) NSString* objId;
#property (nonatomic,copy) NSString* userId;
#property (nonatomic,copy) NSString* checkpointId;
#property (nonatomic,retain) NSDate* dateAdded;
#property (nonatomic,retain) NUBCheckpointModel* checkpoint;
The code is probably the best way to see what I am trying to do:
AcInfo.h:
#interface AcInfo : NSManagedObject {
#private
}
#property (nonatomic, retain) NSString *registrationNumber;
#end
AcInfo.m:
#implementation AcInfo
#dynamic registrationNumber;
#end
AnotherClass.h:
#interface AnotherClass : NSObject {
}
#property (nonatomic, retain) AcInfo *detailItem;
#property (nonatomic, retain) IBOutlet UITextField *registrationNumberTextField;
- (void)setDetailItemValueFromUIElement:(id *)uiElement forAcInfoTarget:(id *)acInfoTarget;
#end
AnotherClass.m:
#import "AcInfo.h"
#implementation AnotherClass
#synthesize detailItem, registrationNumberTextField;
- (void)viewDidLoad
{
[super viewDidLoad];
registrationNumberTextField.text = #"Test";
// I expect this to set detailItem.registrationNumber to the value of
// registrationNumberTextField.text (Test) but it doesn't change anything!
setDetailItemValueFromUIElement:registrationNumberTextField forAcInfoTarget:detailItem.registrationNumber;
}
- (void)setDetailItemValueFromUIElement:(id *)uiElement forAcInfoTarget:(id *)acInfoTarget
{
if ([(id)uiElement isKindOfClass:[UITextField class]]) {
// This doesn't do anything when it returns!
(NSString *)acInfoTarget = (UITextField *)uiElement.text
return;
}
}
#end
In short, I want acInfoTarget to call the getter [detailObject registrationNumber] and the setter [detailObject setRegistrationNumber] in the setDetailItemValueFromUIElement: function...
You can set or read properties by name using
// setter
NSString *propertyName = #"myProperty";
[object setValue:newValue forKey:propertyName];
// getter
id value = [object valueForKey:propertyName];
This is slower than using the normal dot notation, though, and it's frequently (though not always) a sign of poorly-designed code.
Also note that id is a pointer type, so you probably don't actually mean "(id*)".
Your code wants to look something like this, I think:
- (void)setDetailItemValueFromUIElement:(id)uiElement forAcInfoTarget:(NSString*)acInfoTarget {
if ([(id)uiElement isKindOfClass:[UITextField class]]) {
NSString *newValue = ((UITextField*)uiElement).text;
[self.detailItem setValue:newValue forKey:acInfoTarget];
}
}
Properties are just syntax sugar for a couple of accessor methods. They are not, in essence, variables so you shouldn't treat them as such. If you want to affect a property, then what you wanting to do is call a method. So you should pass a id and selector parameter and not pointer to a variable type.
Ok, so I have this, but it wont work:
#interface UILabel (touches)
#property (nonatomic) BOOL isMethodStep;
#end
#implementation UILabel (touches)
-(BOOL)isMethodStep {
return self.isMethodStep;
}
-(void)setIsMethodStep:(BOOL)boolean {
self.isMethodStep = boolean;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
if(self.isMethodStep){
// set all labels to normal font:
UIFont *toSet = (self.font == [UIFont fontWithName:#"Helvetica" size:16]) ? [UIFont fontWithName:#"Helvetica-Bold" size:16] : [UIFont fontWithName:#"Helvetica" size:16];
id superView = self.superview;
for(id theView in [(UIView *)superView subviews])
if([theView isKindOfClass:[UILabel class]])
[(UILabel *)theView setFont:[UIFont fontWithName:#"Helvetica" size:16]];
self.font = toSet;
}
}
#end
If I take out the getter and setter methods then it doesn't work it tells me I need to create some getter and setter methods (or use #synthesize - but putting #synthesize in the #implementation throws an error too). But with the getter and setter methods I get an EXC_BAD_ACCESS and a crash. Any ideas? Thanks
Tom
It is not possible to add members and properties to an existing class via a category — only methods.
https://developer.apple.com/library/content/documentation/General/Conceptual/DevPedia-CocoaCore/Category.html
One possible workaround is to write "setter/getter-like" methods, that uses a singleton to save the variables, that would had been the member.
-(void)setMember:(MyObject *)someObject
{
NSMutableDictionary *dict = [MySingleton sharedRegistry];
[dict setObject:someObject forKey:self];
}
-(MyObject *)member
{
NSMutableDictionary *dict = [MySingleton sharedRegistry];
return [dict objectforKey:self];
}
or — of course — write a custom class, that inherits from UILabel
Note that nowadays an associated object can be injected during runtime. The Objective C Programming Language: Associative References
Checked all answers and did not find the most common solution:
#import <objc/runtime.h>
static void const *key;
#interface ClassName (CategoryName)
#property (nonatomic) BOOL myProperty;
#end
#implementation ClassName (CategoryName)
- (BOOL)myProperty {
return [objc_getAssociatedObject(self, key) boolValue];
}
- (void)setMyProperty:(BOOL)value {
objc_setAssociatedObject(self, key, #(value), OBJC_ASSOCIATION_RETAIN);
}
#end
swift:
private struct AssociatedKeys {
static var keyName = "keyName"
}
extension Foo {
var bar: Any! {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.keyName)
}
set {
objc_setAssociatedObject(self, &AssociatedKeys.keyName , newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
}
}
There is actually a way, which may not be ideal, but does work.
For it to work, you will need to create a category for a class X and can only be used on subclasses of the same X (e.g. category UIView (Background) can be used with class MyView : UIView, but not directly with UIView)
// UIView+Background.h
#interface UIView (Background)
#property (strong, nonatomic) NSString *hexColor;
- (void)someMethodThatUsesHexColor;
#end
// UIView+Background.h
#implementation UIView (Background)
#dynamic hexColor; // Must be declared as dynamic
- (void)someMethodThatUsesHexColor {
NSLog(#"Color %#", self.hexColor);
}
#end
Then
// MyView.m
#import "UIView+Background.h"
#interface MyView : UIView
#property (strong, nonatomic) NSString *hexColor;
#end
#implementation MyView ()
- (void)viewDidLoad {
[super viewDidLoad];
[self setHexColor:#"#BABACA"];
[self someMethodThatUsesHexColor];
}
#end
Using this method, you will need to "redeclare" your properties, but after that, you can do all of its manipulation inside your category.
You could inject an associated object during runtime.
#import <objc/runtime.h>
#interface UIView (Private)
#property (nonatomic, assign) CGPoint initialTouchPoint;
#property (nonatomic, strong) UIWindow *alertWindow;
#end
#implementation UIView (Private)
#dynamic initialTouchPoint, alertWindow;
- (CGPoint)initialTouchPoint {
return CGPointFromString(objc_getAssociatedObject(self, #selector(initialTouchPoint)));
}
- (void)setInitialTouchPoint:(CGPoint)initialTouchPoint {
objc_setAssociatedObject(self, #selector(initialTouchPoint), NSStringFromCGPoint(initialTouchPoint), OBJC_ASSOCIATION_RETAIN);
}
- (void)setAlertWindow:(UIWindow *)alertWindow {
objc_setAssociatedObject(self, #selector(alertWindow), alertWindow, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (UIWindow *)alertWindow {
return objc_getAssociatedObject(self, #selector(alertWindow));
}
#end
EDIT: Warning: This property would have a unique value for all the instances of the class.
This worked for me, but only because I had only one instance of this class in my app.
#import <AVFoundation/AVFoundation.h>
#interface AVAudioPlayer (AstroAVAudioPlayer)
#property (nonatomic) BOOL redPilot;
#end
#import "AVAudioPlayer+AstroAVAudioPlayer.h"
#implementation AVAudioPlayer (AstroAVAudioPlayer)
BOOL _redPilot;
-(void) setRedPilot:(BOOL)redPilot
{
_redPilot = redPilot;
}
-(BOOL) redPilot
{
return _redPilot;
}
#end
A solution that I found to this was to just give each object that you want flagged a unique tag.
I made a UILabel category to add custom fonts to all my labels but on some i wanted them to be bold so i did this ->
- (void) layoutSubviews {
[super layoutSubviews];
[self addCustomFont];
}
- (void) addCustomFont {
if (self.tag == 22) {
[self setFont:[UIFont fontWithName:SEGOE_BOLD size:self.font.pointSize]];
}else{
[self setFont:[UIFont fontWithName:SEGOE_LIGHT size:self.font.pointSize]];
}
}
It seems as if since Xcode 7 (7.0.1, 7A1001), properties are supported in categories. I noticed that Xcode generates categories now for Core Data subclasses.
For example, I got the files:
Location+CoreDataProperties.h
#import "Location.h"
NS_ASSUME_NONNULL_BEGIN
#interface Location (CoreDataProperties)
#property (nullable, nonatomic, retain) NSNumber *altitude;
#property (nullable, nonatomic, retain) NSNumber *latitude;
#property (nullable, nonatomic, retain) NSNumber *longitude;
#end
NS_ASSUME_NONNULL_END
Location+CoreDataProperties.m
#import "Location+CoreDataProperties.h"
#implementation Location (CoreDataProperties)
#dynamic altitude;
#dynamic latitude;
#dynamic longitude;
#end
So looks like properties in categories might work now. I haven't tested on non-Core Data classes.
What I've noticed is that they do include the category file back into the original class:
Location.h
#interface Location : NSManagedObject
#end
#import "Location+CoreDataProperties.h"
This allows the original class to edit the properties specified by the category.