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iOS Swift Functions and Optionals Parameters and Tuples Tuples

Samar Khanna
Samar Khanna
1,757 Points
Posted by Samar Khanna
Samar Khanna
1,757 Points

Why won't switching changing the initial value of "found" to "false" work?

this the code:

func searchNames (#name:String) -> (Bool,String) {
    let myFriends = ["h","i","j","k","l"]

    var found = (true, "\(name) is a friend of mine")

    for n in myFriends {
        if name != n {
            found = (false,"\(name) is not a friend of mine")
        }
    }
    return found
}

searchNames(name: "i")

The result pane is showing me false

Samar Khanna
Samar Khanna
1,757 Points
Samar Khanna
Samar Khanna
1,757 Points

Sorry the code looks a bit odd, but it starts from "func searchNames..."

2 Answers

Steve Hunter
Steve Hunter
57,712 Points

Here's how I would achieve the same aim as your code:

func mySearchNames (#name: String) -> (Bool, String) {
    let myFriends = ["h","i","j","k","l"]

    for n in myFriends {
        if n == name {
            return (true, "\(name) is a friend of mine")
        }
    }
    return (false, "\(name) is not a friend of mine")
}

Here, we just go straight into the loop without declaring a variable to hold the two possible results. We have one test, we look if the current element of the myFriends array is the same as the name parameter passed into the function.

If the test is true, i.e. n == name then we immediately return the tuple you required. That leaves the loop immediately.

If we get to the end of the loop without running the return line, that means that none of the n elements equalled name. So, we return the opposite tuple and exit the method.

I hope that makes sense. This method has fewer lines of code and a clear line of execution. The logic of the tests doesn't require double negative results to occur so the execution route is clearer and uses simpler logic.

Steve.

Samar Khanna
Samar Khanna
1,757 Points
Samar Khanna
Samar Khanna
1,757 Points

Thank you so so much. You have been really helpful. I didn't understand your first 2 answers, but this one makes sense

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Because the loop iterates through the whole array of letters. The last one in the array is l. That doesn't equal i so it returns, correctly, false.

Also, there's nothing to set the resut back to true. So, before the first iteration has happened, the start of your found variable is true. The first iteration then occurs. In that scenario, name != n so found is set to false.

The next iteration name == n but that just skips the if block, rather than doing anything to the string/tuple so found remains the same to the end of the for loop, and false is returned.

You need to fix two things. First, you need to have the test set both conditions. Second, you need to get out of the loop as soon as the desired result is reached, rather than testing the whole array. i think you may need to reverse the test too, rather than looking for inequality, look for equality.

I'll give you a couple of fixes. One better than the other.

Steve.

Steve Hunter
Steve Hunter
57,712 Points

Using your code as a basis, although I stand by the above, adding a couple of lines gets the result you are expecting:

func searchNames (#name:String) -> (Bool,String) {
    let myFriends = ["h","i","j","k","l"]

    var found = (true, "\(name) is a friend of mine")

    for n in myFriends {
        if name != n {
            found = (false,"\(name) is not a friend of mine")
        } else {
            found = (true, "\(name) is a friend of mine") // set the tuple again
            return found  // get out of the loop before the next test is true, i.e. name != n
        }
    }
    return found
}

searchNames(name: "i")

This now exits the loop as soon as name != n is false and returns true.

That double/triple negative is one of the problems with this code. If you are looking to return true when a != test returns a false the code is confused and some simpler syntax is likely to create much clearer code. Currently you are testing for when your not equal condition is false so you can return true.

Steve.