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iOS Swift Functions and Optionals Optionals What is an Optional?

James Stott
James Stott
11,560 Points
Posted by James Stott
James Stott
11,560 Points

How does `let name = value` resolve to a boolean?

In the 'What is an optional' video the following code is displayed:

if let culprit = findApt("102") {
    println("Apt Found: \(culprit)")
}

where findApt() returns an optional

How does this work? Does the let command return a boolean when invoked?

2 Answers

landonferrier
landonferrier
25,097 Points

James, remember, when the compiler compiles an if statement, there are only two outcomes of the value in the if statement, true or false. In the case of the example code you have provided there are two outcomes when that code in compiled. If the findApt() method returns a value, any value, it will be true and executed. If the findApt() method doesn't return any value, the if will not pass and the code inside the statement will never be executed.

If you have any questions, feel free to ask!

Jeanne Merle
Jeanne Merle
3,390 Points
Jeanne Merle
Jeanne Merle
3,390 Points

In fact, it means "If I can assign a value tu culprit, THEN it's true" , doesn't it ?

Edward Ulpindo
Edward Ulpindo
700 Points
Edward Ulpindo
Edward Ulpindo
700 Points

That makes sense. But if all you need is a non-nil value to evaluate the conditional, why does if findApt() throw an error (as it did in Amit's lesson)?

sieder villareal
sieder villareal
4,016 Points
sieder villareal
sieder villareal
4,016 Points

it does return a boolean if you think about it, because the code you posted is a conditional and it is expected that it will return true or false according to the condition. let command means "culprit" it is a constant, immutable, value can't be change.