Swift Functions Exercise

Swift Function Exercise

Sample Example:
Here's how to write a basic function in Swift that adds two numbers:

```
func add(_ x: Int, _ y: Int) -> Int {
    return x + y
}
// Using the function:
let result = add(5, 3)
print(result) // Prints: 8
```

Your Task:
Write a function called processOrder that:

Takes a string in the format "itemName:quantity@price"
Returns a tuple of (itemName: String, total: Double, isValid: Bool)

Requirements:
Extract the item name, quantity, and price from the string
Quantity must be converted from string to Int
Price must be converted from string to Double
Return ("", 0.0, false) if the string format is invalid
Total should be quantity * price

Test Cases:
processOrder("iPhone:[email protected]")     // Returns ("iPhone", 1999.98, true)
processOrder("Coffee:[email protected]")       // Returns ("Coffee", 13.50, true)
processOrder("Laptop:[email protected]")   // Returns ("", 0.0, false)
processOrder("Invalid String")       // Returns ("", 0.0, false)