please can someone explain why we have the (key,value) and why in brackets ?.

Hello Jon:

When using a for in loop while iterating through a dictionary, you should use a tuple.

Seems like world is a dictionary that holds capitals, and they want those to be appended to their corresponding continent.

for (key, value) in world {
 // Do work here
}

What is happening here is that the for in loop is iterating through the dictionary, and temporarily assigning the keys and values to these two constants key & value, where key holds the keys of the dictionary, and value holds the values of each key. Sounds a bit complicated, but it's not as bad.

// Dictionary
var cars = ["Key1":"BMW" , "Key2":"Ferrari"]

// This dictionary holds 2 items.

cars["Key1"] // Will return BMW

Now, in order for us to access these values, we can use a switch to switch on the keys, and get in return their value.

var cars = ["Key1":"BMW" , "Key2":"Ferrari"]

for (key, value) in cars {

    switch key {
    case "Key1" :
        print(value) // Will print BMW
    case "Key2":
        print(value) //Will print Ferrari
    default: break
    }  
}
}

To read more about tuples, you can go here and read on Basics. If you scroll down, you'll find tuples.

Hope this makes more sense to you now.

If any other questions, please let me know.

Good luck