A thread-safe wrapper around a value.
The following code may cause crashes or data errors in concurrent situations:
var numbers = [1, 2, 3, 4, 5]
DispatchQueue.concurrentPerform(iterations: 10) { _ in
if let firstEven = numbers.first(where: { $0 % 2 == 0 }) {
print(firstEven)
}
// Another thread modifies the array concurrently
numbers.append(Int.random(in: 1...100))
}In this case, the first(where:) and append operations may cause data races, leading to program instability.
The code is modified using Protector:
let numbers = Protector([1, 2, 3, 4, 5])
DispatchQueue.concurrentPerform(iterations: 10) { _ in
if let firstEven = numbers.read ({ ns in
ns.first(where: { $0 % 2 == 0 })
}) {
print(firstEven)
}
// Another thread modifies the array concurrently
numbers.write({ $0.append(Int.random(in: 1...100)) })
}After the modification, there will be no data competition problem.
