In Swift, How to understand the "inline closure"?

Question

everyone. When I read the Closures, there is not a definition for inline closures.

Q1: How to understand inline in "inline closure"?
Q2: What is the different between "inline closure" and normal closure?

Thanks in advance for your help!

Answer 1

An inline value is a value that's used directly, without first being assigned to an intermediate variable. Consider these two examples:

let number = 1
print(number)

Here, 1 is assigned to an intermediate variable, number, which is then printed.

print(1)

Here, 1, is an inlined integer literal, which is printed directly.

The same applies to closures.

let evenNumberFilter: (Int) -> Bool = { $0 % 2 == 0 }
print((0...10).filter(evenNumberFilter))

Here, { $0 % 2 == 0 } is a closure (of type (Int) -> Bool) that's assigned to the intermediate variable evenNumberFilter before being used.

print((0...10).filter{ $0 % 2 == 0 })

In this case, { $0 % 2 == 0 } was used directly. It's an inline closure.