The below code will print `B` ```null?.let { p...

# compose

[theapache64]

The below code will print B

null?.let {
    println("A")
} ?: println("B")

but the below code doesn’t render B

null?.let {
    Text(text = "A")
} ?: Text(text = "B")

Why? 🤔

[theapache64]

stackoverflow https://stackoverflow.com/questions/71310558/composable-doesnt-render

[Filip Wiesner]

Maybe related to this?

[Alexander Maryanovsky]

Indeed. https://issuetracker.google.com/issues/204600178

[Alexander Maryanovsky]

but it’s also an anti-pattern, as I mentioned in that same thread

[theapache64]

@Alexander Maryanovsky
Can’t say “an anti-pattern”. Should belong to “personal preference” IMO.
The above given sample is a very minimized version to reproduce the bug. When we have deep chaining and want a default behaviour when it’s null, this’ll come handy.

[theapache64]

@Filip Wiesner Yes. It’s a bug.

[Paul Woitaschek]

I'd strongly vote for anti pattern as well. Just relying on the position of the unit returning expression is error prone.

[mattinger]

have you tried using a run { } block around the null condition:

null?.let {
Text(text = “A”)
} ?: run { Text(text = “B”) }

[Alexander Maryanovsky]

@theapache64 It’s an antipattern because if the value of the last expression inside the let happens to be null, you will have the part after the ?: evaluated as well.

[theapache64]

@mattinger Yes. It didn’t work.
@Paul Woitaschek Sorry, I’d like to understand why you consider this is an anti-pattern.
Let me explain my point.

class User(val job: Job?)
class Job(val title: String?)

val user: User? = User(job = null)

// Option #1
user?.job?.title?.let { Text("Job title is $it") } ?: Text("No job title found")

// Option #2
val jobTitle = user?.job?.title
if (jobTitle == null) {
    Text("Job title is $jobTitle")
} else {
    Text("No job title found")
}

Here, I agree #2 gives a little more readability, but #2 helps us to avoid declare a local variable. What problem do you see with #1 ? 🤔

[Alexander Maryanovsky]

See above

[theapache64]

Ohhkay. Now I got it. Agreed. I didn’t think of that. Thanks guys.

[Alexander Maryanovsky]

Feel free to star the issue I linked above; maybe Google will fix it faster.

[theapache64]

Sure 👍