Easily manage image type with sealed classes

5AbhishekSaxena — Tue, 30 Nov 2021 15:06:58 +0000

This post was originally posted on medium.

With the introduction of sealed classes in Kotlin, it opened up a way to easily handle restricted hierarchies.
The most common use case of a sealed class is with the handling Result<T> of an API response.

…..but there are way more applications of the sealed classes than you can imagine. I'll discuss one of them here, which would be to handle image type in android.
The source of the image can either be remote, i.e, a URL or local storage. Since the resource can come from only these two types, it makes a perfect use case for the sealed classes.

sealed class UiImage {
    data class LocalImage(val imageRes: Int) : UiImage()
    data class RemoteImage(val imageUrl: String) : UiImage()
}

You can use the Image everywhere in the project and easily refer to either of the two.

Example:

data class Student(
    val name: String,
    val profileImage: UiImage
)

fun main() {
    val abhishekSaxena = Student("Abhishek Saxena", UiImage.RemoteImage("https://remoteurl.com/images/sample.png"))
    val johnDoe = Student("John Doe", UiImage.LocalImage(R.drawable.default_profile_pic))
}

Additionally, you can easily load images with the image loading library like Glide

 fun ImageView.loadImage(
    image: UiImage
) {
    Glide.with(this.context)
        .load(
            when (image) {
                is UiImage.LocalImage -> image.imageRes
                is UiImage.RemoteImage -> image.imageUrl
            }
        )
        .into(this)
}

You can use it with Jetpack Compose.

You can create a composable that consumes a UiImage, that in-app code ends up being remote, but for previews, you can supply a drawable res, so I can see the full behavior

// Component
@Composable
fun UserProfile(
  profileImage: UiImage,
)

// In production
UserProfile(
  profileImage = UiImage.RemoteImage(avatarURL)
)

// In preview
@Preview
@Composable
fun UserProfilePreview() {
  UserProfile(
    profileImage = UiImage.LocalImage(R.drawable.preview_profile_image)
  )
}

Conclusion

Kotlin sealed classes are really powerful when you have a strict hierarchy of classes. Herewith the images, you can even extend the usage to text as it can be directly passed as a string or as a reference of the string resource.

A special thanks to Adam McNeilly for the feedback and suggestions.

Thank you very much for reading the article. I hope you liked it. Do you have any feedback? Comment below or reach out to me on Twitter.

Cover photo credits:

Photo by Pablo Arroyo on Unsplash

Did you stop contributing after making 4 Pull Requests?

5AbhishekSaxena — Wed, 28 Oct 2020 19:53:19 +0000

Who am I?

Just like you, I am a developer who is trying to write decent code and wants to do something great one day. Hi, and my name is Abhishek Saxena, I am a native android developer who is slowing shifting towards enterprise full-stack java development. I try to share my knowledge via Youtube, Instagram, and in discord communities.

Why was this Hacktoberfest so special for me?

This Hacktoberfest was different unlike the one in 2018 when I was very new to git and programming in general.

So, you may ask how was it different? The obvious answer would be I was more experienced this time, but there's more to it.

This year, I joined a small discord community. I mentored the fellow developers, guided them, taught them the basics of git, and how to make their first pull request.

Not only that, I even conducted a small event wherein I asked them to pick any project of their choice from each other's GitHub and asked them to review it, find improvements or give feedback.

With this, not only they inculcated a new skill of reviewing other's code but also to give constructive feedback based on their understanding. Some of them even went a step ahead and made PRs.

Overall it was an amazing experience for me as a mentor and also special as I was able to share my knowledge and give back to the community.

I'd like to end by saying,
"If you know something, share it, maybe you'll be part of their success story"