UseSumOfInsteadOfFlatMapSize.md

Pattern: Missing use of sumOf

Issue: -

Description

Turn on this rule to flag flatMap and size/count calls that can be replaced with a sumOf call.

Example of incorrect code:

class Foo(val foo: List<Int>)
list.flatMap { it.foo }.size
list.flatMap { it.foo }.count()
list.flatMap { it.foo }.count { it > 2 }
listOf(listOf(1), listOf(2, 3)).flatten().size

Example of correct code:

list.sumOf { it.foo.size }
list.sumOf { it.foo.count() }
list.sumOf { it.foo.count { foo -> foo > 2 } }
listOf(listOf(1), listOf(2, 3)).sumOf { it.size }

Further Reading

• Detekt - UseSumOfInsteadOfFlatMapSize