[iOS][Android] Use lazySequence on operations such as map or filter

[PierreEc]

Privilégier les lazysequences pour optimiser des cycles CPU inutiles

https://developer.apple.com/documentation/swift/lazysequence

Example:

(1...100_000)
    .map { $0 * $0 }
    .filter { $0.isMultiple(of: 10) }
    .first(where: { $0 > 100 } )

With lazy:

(1...100_000)
    .lazy
    .map { $0 * $0 }
    .filter { $0.isMultiple(of: 10) }
    .first(where: { $0 > 100 } )

[PierreEc]

There is the same with kotlin with SequenceOf:

SequenceOf

[PierreEc]

Use lazySequence on operations such as map or filter

Platform

OS	OS version	Langage.
iOS/iPadOS/WatchOS/tvOS - Android	-	Swift / Kotlin

Main caracteristics

ID	Title	Category	Sub-category
-		Environment	Optimized API

Severity / Remediation Cost

Severity	Remediation Cost
Major	Minor

Rule short description

Prefer lazysequences for optimize useless CPU cycles

Rule complete description

Text

Prefer lazysequences for optimize useless CPU cycles when you use operations such as map and filter

HTML

<p>Prefer lazysequences for optimize useless CPU cycles</p>
<p>
<a href="https://developer.apple.com/documentation/swift/lazysequence">Doc apple LazySequence</a>
<a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.sequences/sequence-of.html">Doc android SequenceOf</a>
</p>
<p>
<img src="https://user-images.githubusercontent.com/18304803/230103031-275bdf34-8f45-45da-abc5-8f0dd97a72a6.png" />
</p>

Implementation principle

• Verify if you use ListOf on Kotlin
• Verify if you use lazy when you use operations on a collection

[olegoaer]

This rule can now be implemented with the arrival of the Android Kotlin plugin @47tibo ;)

[47tibo]

Interesting way of "activating" lazy in Swift 🙂 @olegoaer we can add this rule to kotlin, but it is a bit more complex than that.

In short, it depends on the type of the operators, their order in the chain and also the size of the collection.