var optionalname: String? = "QUAN"
let name1 = optionalname
var greeting1 = "Hello, \(name1)"
print(greeting1)
if let name2 = optionalname {
var greeting2 = "Hello, \(name2)"
print(greeting2)
}
print (greeting1) ergibt:Swift Abwickeln optional in bedingten
"Hallo, Optional (" QUAN ") \ n"
print (Greeting2) ergibt:
"Hallo, QUAN \ n"
Kann mir jemand helfen, die Gründe für den Unterschied zu erklären? Vielen Dank!
Lookup "optionale Bindung" in der Swift Referenz. –
Verwandte: http://stackoverflow.com/questions/29717210/when-should-i-compare-an-optional-value-to-nil, http://stackoverflow.com/questions/33769366/why-use-optional -Bindung, –