Swift atomic property using @propertyWrapper

Atomic.swift

// Requires Swift 5.1 (Xcode 11.1+).
//
// Using pthread_rw_lock allows to minimize system resources 
// and prevent creation of DispatchQueue per each @Atomic property.
//

@propertyWrapper
final class Atomic<Value> {
    
    var value: Value
    var lock = pthread_rwlock_t()
    
    init(wrappedValue: Value) {
        self.value = wrappedValue
    }
    
    var wrappedValue: Value {
        get {
            pthread_rwlock_rdlock(&lock)
            defer { pthread_rwlock_unlock(&lock) }
            
            return value
        }
        set {
            pthread_rwlock_wrlock(&lock)
            defer { pthread_rwlock_unlock(&lock) }
            
            value = newValue
        }
    }
    
    func mutate(_ transform: (inout Value) -> Void) {
        pthread_rwlock_wrlock(&lock)
        defer { pthread_rwlock_unlock(&lock) }
        
        transform(&value)
    }
}


// Usage example

class A {
    @Atomic var text: String = ""
    
    func foo() {
        for i in 1..<10000 {
            DispatchQueue.global().async {
                self.text = String(i)
            }
        }
    }
    
    func bar() {
        // Assume you want to change value atomically dealing with its previous value
        _text.mutate { $0 += "-bar" }
    }
}

// main

let a = A()
a.foo()
a.bar()

RunLoop.main.run()