♻️ Reusing Image with Template render mode in iOS

UIImage comes with property "renderingMode" from iOS 7 onwards. It can be set either 'alwaysTemplate' or 'alwaysOriginal'. This enum property helps us to re-use images that may thin your app size too.

Let's get into to a real scenario !

I have added button as heart icon that gives like or dislike functionality for a picture.
As you can see in the result below, heart image turns red when liked and stays gray when disliked. In such cases only one image asset can be used.

Considering a UIButton object already created and added as a subview in the project, let's start with functionality. Again, I have only one image with name 'heart' in the asset folder (with gray fill). Using same image, I can create 2 instances of UIImage objects using rendering modes.

 let notLikedImage = UIImage.init(named: "heart")?.withRenderingMode(.alwaysOriginal)

 let likedImage = UIImage.init(named: "heart")?.withRenderingMode(.alwaysTemplate)

Now, set the images for selected and normal state.

 self.likeButton.setImage(notLikedImage, for: .normal)

 self.likeButton.setImage(likedImage, for: .selected)

Set the button tint color which will be rendered for Template mode. In our case, when user liked picture, button turns to red color.

 self.likeButton.tintColor = .red

Set target method for button event for example :

 self.likeButton.addTarget(self, action: #selector(updatedButton), for: .touchUpInside)

Also, in implement the button selection state toggle.

 @objc func updatedButton(){

    self.likeButton.isSelected = !self.likeButton.isSelected

}

That's it. Now you can see the final result - When user selects the button, it turns red from template mode. When deselects, it turns back to original image.!

Bonus tip :

Feels odd when button tapped it highlights? We can remove the button by setting 'false' to property 'adjustsImageWhenHighlighted'.

 self.likeButton.adjustsImageWhenHighlighted = false

Animating label text update - choosing a better way

Recently I published a countdown app . At one point of development - I have to show a timer on a UILabel which ticks on each seconds. As usual I started setting text to a label object - self .timerLabel.text = someString Easy piece of cake right !? But wait ... it won't take much user attention when timer ticks on every seconds. So I decided to make use of a simple animation while label gets text update. I found there are dozens of ways to animate a label. In this short article, I listed 3 best way you can animate text on a label. ( Spoiler Alert 👀- I decided to go with 3rd option) 1. Fade In - Fade out animation : CATransition class has got transition type `fade`. With timing function of CATransition - I was able to see the below result. let animation: CATransition = CATransition () animation.timingFunction = CAMediaTimingFunction (name: CAMediaTimingFunctionName .easeInEaseOut) animation.type = CATransitionType .fade animation.subtype = C...

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UICollectionViewCell shows with wrong size on First time - Solved

We commonly use Collection view where its cell size calculated run time. The flow layout delegate is responsible to return individual cell sizes. BUT in most of the cases, delegate method `collectionView: layout sizeForItem:` expects cell size too early. Before generating actual cell size. extension YourViewController : UICollectionViewDelegateFlowLayout { func collectionView ( _ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { return CGSize (width: externalWidth, height: externalHeight) } } For instance, if a cell size depends on external view and its frame is not yet ready - results with wrong (or outdated) cell size. Typically happens for the first time view controller laid out all views. You can find similar queries in StackOverflow community : Collection view sizeForItemNotWorking UICollectionViewCell content wrong size on first load How to refresh UICollec...

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