i can't understand why?

i meant why we can't write some thing like that : let proposition = Proposition.True("it is a proposition"),Proposition.False("it's not a prposition") !!

Are you sure that you don't want to use raw value instead of associated value? That way you can just get the rawValue property once you set .True or .False. Let me show you what I mean.

enum Proposition: String {
    case True = "it is a proposition",
    False = "it is not a proposition"
}
let proposition = Proposition.True

switch proposition {
case .True:
    print(proposition.rawValue)
case .False:
    print(proposition.rawValue)
}
// prints out: it is a proposition

Let me know if you're trying to do something else.

Noor, I am not sure if my answer will help, but I think you are mixing between enums raw values and enum associated vaules. A raw value is when you give the value during the creating of the enum:

enum Size: Int {
case Big = 1 , Medium = 2, Small = 3
}
let biggestSize = Size(rawValue: 1)

while an associated value is a value assigned when creating an instance of the enum, ex:

enum Size {
case Big (Int) , Medium (Int), Small(Int)
}
let biggestSize = Size.Big(41)

notice that in the case of associated values, we give the value when creating an instance of the enum.

regarding the other question: we assign let or var to the line:

case.True(let T)

to extract the associated value we parsed before. hope my explaining helped.

Ghaith Ali شكراً لك غيث ، اجابتك على السؤال الثاني كانت افية :)