Apply global class to UIImage - ios

Question

Now I'm not sure if this is possible in Objective-C but I would expect it should be.
I have multiple images across my storyboard using the following/similar code on UIImages
cell.followingImage.layer.cornerRadius = cell.followingImage.frame.size.width / 2;
cell.followingImage.clipsToBounds = YES;
I want to optimise the code. I know you can apply classes to objects but I have never done this before. Is it possible to apply the class via the storyboard and automatically run that code without referencing and adding it to every controller?
So if a class is attached to the UIImage it would just run that code and make the UIImage a circle? This is probably really simple...
If I was to subclass a UIimage I'm not sure where to put the above code?

Answer 1

Try making a category of UIImage. Include everything you want in this custom category class like your cornerRadius and your clipToBounds code. Then when you init the images, don't init the images with [UIImage new] but with [customImageCategoryName new[. Now, all these images will, by default, have those two lines of code. The following link will show you how to create a category in Xcode How do I create a category in Xcode 6 or higher?

Answer 2

Do place that code in
-(instancetype)initWithCoder:(NSCoder *)aDecoder method , -(instancetype)initWithFrame:(CGRect)frame method
and init method.
That way if the imageview is from storyboard the initWithCoder will get called and other methods get called when it is programatically added.

Answer 3

As none of the other answers really worked nor were complete enough I used User Defined Runtime Attributes instead.
To avoid the need to write it in code I added
layer.cornerRadius with Number attribute half the width.
layer.masksToBounds with Bool attribute as YES

Answer 4

Method swizzling is a very good option to achieve this.
Create a UIImageView category class and swizzle initWithCoder: method
#import "UIImageView+MethodSwizzling.h"
#import <objc/runtime.h>
#implementation UIImageView (MethodSwizzling)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
SEL originalSelector = #selector(initWithCoder:);
SEL swizzledSelector = #selector(xxx_initWithCoder:);
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
// ...
// Method originalMethod = class_getClassMethod(class, originalSelector);
// Method swizzledMethod = class_getClassMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
}
else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
});
}
#pragma mark - Method Swizzling
- (id)xxx_initWithCoder:(NSCoder*)aDecoder {
[self xxx_initWithCoder:aDecoder];
self.layer.cornerRadius = self.frame.size.width / 2;
self.layer.masksToBounds = YES;
NSLog(#"xxx_initWithCoder: %#", self);
return self;
}
You don't have to create subclass of UIImageView and do not need to change your object's class everywhere in XIB/Storybord.
Click here to know about method swizzling.

Answer 5

What your "answer" suggests is that you are using UIImageViews in the Storyboard. The best approach would be to create a subclass of UIImageView, e.g.:
//MyImageView.h
#import <UIKit/UIKit.h>
#interface MyImageView : UIImageView
#end
The code to adapt the cornerRadius and the clipsToBounds should be added to the MyImageView.m:
//MyImageView.m
- (id)layoutSubviews {
[super layoutSubviews];
self.layer.cornerRadius = self.view.frame.width.width / 2
self.layer.clipsToBounds = true;
// this line may be only needed in init since the clipsToBounds does not change due to autoLayout.
}
After writing that code, you need to set the class attribute of all UIImageViews in the Storyboard (all those that should be circular) to MyImageView instead of the default UIImageView.