I am new to Swift and trying to figure out the Optional concept. I have a small piece of code in Playground which is giving me "Variable binding in a condition requires an initializer" error. Can someone please explain why and how do I fix it?
I only want to print "Yes" or "No" depending on if "score1" has a value or not. Here is the code:
import Cocoa
class Person {
var score1: Int? = 9
func sum() {
if let score1 {
print("yes")
} else {
print("No")
}
}//end sum
}// end person
var objperson = person()
objperson.sum()
5 Answers
The if let statement takes an optional variable. If it is nil, the else block or nothing is executed. If it has a value, the value is assigned to a different variable as a non-optional type.
So, the following code would output the value of score1 or "No" if there is none:
if let score1Unwrapped = score1
{
print(score1Unwrapped)
}
else
{
print("No")
}
A shorter version of the same would be:
print(score1 ?? "No")
In your case, where you don't actually use the value stored in the optional variable, you can also check if the value is nil:
if score1 != nil {
...
}
Writing
if let score1 {
doesn't make sense. If you want to see if score has a value, use
if score1 != nil {
or
if let score = score1 {
The last case binds a new non-optional constant score to score1. This lets you use score inside the if statement.
The code in your question is similar to something I saw in the swift book and documentation and they are correct.
Your playground is just using an old version of swift which currently doesn't support this syntax. Using a beta version of XCode should fix
the problem is that if let assumes you want to create a constant score1 with some value. If you just want to check if it contains a value, as in not nil you should just do it like below:
if score1! != nil {
// println("yes")
So your full code would look like this:
class Person {
var score1: Int? = 9
func sum() {
if score1 != nil {
println("yes")
}
else {
println("no")
}
}
}
var objperson = Person()
objperson.sum()
You can unwrap it using this:
import Cocoa
class Person {
var score1: Int? = 9
func sum() {
print("\(score1 != nil ? "YES" : "NO")")
}
}
And then call it like:
var objperson = Person()
objperson.sum()
