gcd3.swift

//Single BlockOperation 
var result:Int?
let multiplication = BlockOperation{
    result = 5 * 10
}
multiplication.start()
result
[/code]

Multiple operations using BlockOperation:

[code lang="swift"]
let pairOfNumbers = [(2, 3), (5, 10), (4, 5)]
let blockOperations = BlockOperation()

for pair in pairOfNumbers{
    blockOperations.addExecutionBlock {
        let result = pair.0 * pair.1
        print(result)
    }
}

blockOperations.start()