SWIFT Variable used before being initialized [duplicate] - swift

Question

This question already has answers here:
Variable used before being initialized in function
(6 answers)
Closed 4 years ago.
I want to know why this code will not run. The error appears on the very last line (the print statement) (the last "letter grade") and says
"Variable 'letterGrade' used before being initialized"
let score = 86
var letterGrade: Character
if(score >= 90)
{
letterGrade = "A"
}
else if(score >= 80)
{
letterGrade = "C"
}
else if (score >= 70)
{
letterGrade = "C"
}
else if (score >= 60)
{
letterGrade = "D"
}
else if (score > 0)
{
letterGrade = "F"
}
print("Your letter grade is \(letterGrade)")

Answer 1

Yes, it is used before being assigned a grade (the compiler does not know that you've covered all the cases in your if statements before throwing this error - and in fact you haven't covered zero as #MartinR tells you ).
You could have a default value (in the UK a "U" is ungraded) by changing line 2 to
var letterGrade: Character = "U"
and better still use type inference to say
var letterGrade = "U"
You might also like to use a switch for this type of problem - look in the Swift documents using this link - https://docs.swift.org/swift-book/LanguageGuide/ControlFlow.html
But here is my version of your code using a switch
let score = 86
var letterGrade: Character
switch score {
case 90 ..< 100:
print("A")
case (80 ..< 90):
print("B")
case (70 ..< 80):
print("C")
case (0 ..< 70):
print("D")
default:
print("F")
}
This overcomes the problem of your compiler error.
Hope this helps you.

Answer 2

You cannot use a variable before initializing it (giving it an initial value).
You handled the cases where score >= 90 and score >= 80 and score >= 70 and score >= 60 and score > 0.
What if score was equal to 0? this case isn't handled, if it happened the variable letterGrade will stay uninitialized.
To fix this, you can use the answer by #stevenpcurtis, or you can replace the last else if statement with else only.
Also consider using a switch statement with a default case.