@escaping and @nonescaping closures in Swift

@escaping and @nonescaping closures in Swift

##Escaping
-------------
func getSumOf(array: [Int], handler: @escaping (Int) -> Void) {
    // Step 2: Move work to async queue
    DispatchQueue.global().async {
        
        var sum: Int = 0
        for value in array {
            sum += value
        }
        
        // Step 4: Call later
        handler(sum)
    }
}

func doSomething() {
    // Step 1: Call function
    self.getSumOf(array: [16,756,442,6,23]) { [weak self] sum in
        // Step 5: Executed later
        print(sum)
    }
    
    // Step 3: This runs immediately (before sum is printed)
    print("Function call finished")
}


##Non-Escaping
-------------
func getSumOf(array: [Int], handler: (Int) -> Void) {
    // Step 2: Do work immediately
    var sum: Int = 0
    for value in array {
        sum += value
    }
    
    // Step 3: Call immediately
    handler(sum)
}

func doSomething() {
    // Step 1: Call function
    self.getSumOf(array: [16,756,442,6,23]) { sum in
        // Step 4: Executed immediately
        print(sum)
    }
    
    // Step 5: Runs AFTER closure execution
    print("Function call finished")
}