CODEWITHSUNDEEP
nullkotlinkotlin-null-safety
Michał Jurczuk
Michał Jurczuk

Reputation: 3828

Kotlin null-safety for class properties

How can I avoid using !! for optional properties of class

class PostDetailsActivity {

    private var post: Post? = null

    fun test() {
        if (post != null) {
            postDetailsTitle.text = post.title    // Error I have to still force using post!!.title
            postDetailsTitle.author = post.author

            Glide.with(this).load(post.featuredImage).into(postDetailsImage)

        } else {
            postDetailsTitle.text = "No title"
            postDetailsTitle.author = "Unknown author"

            Toast.makeText(this, resources.getText(R.string.post_error), Toast.LENGTH_LONG).show()
        }
    }
}

Should I create a local variable? I think using !! is not a good practice

Upvotes: 4

Views: 184

Answers (2)

JB Nizet
JB Nizet

Reputation: 692161

You can use apply:

fun test() {
    post.apply {
        if (this != null) {
            postDetailsTitle.text = title
        } else {
            postDetailsTitle.text = "No title"
        }
    }
}

or with:

fun test() {
    with(post) {
        if (this != null) {
            postDetailsTitle.text = title
        } else {
            postDetailsTitle.text = "No title"
        }
    }
}

Upvotes: 5

Michael
Michael

Reputation: 58507

This:

if (post != null) {
    postDetailsTitle.text = post.title    // Error I have to still force using post!!.title
} else {
    postDetailsTitle.text = "No title"
}

Could be replaced with:

postDetailsTitle.text = post?.title ?: "No title"

If the expression to the left of ?: is not null, the elvis operator returns it, otherwise it returns the expression to the right.

Upvotes: 3

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