swift !?

Actually what is the "!" in swift? I know it is represent NOT meaning, but how come in this case it uses like this? Anyone can explain it to me, I'm new to Swift programming language. share improve this answer answered  Apr 4 at 5:21 jefferyleo 106 2 5 16

Swift uses ! in several distinct ways. The one used in these answers is to force unwrap an Optional value. An Optional type is a regular type, e.g. String, which can also be nil and is written String?. If you have a value of type String? and you want to unwrap it to get a value of type String then you use !on the value. In other words, if x: String? you can write x! to get the plain String value wrapped up by the optional. This only works if you know the value is not nil, otherwise you will get a runtime exception. The ! is to signify the potential danger. – rokob Sep 30 at 5:06

Swift uses ! in several distinct ways. The one used in these answers is to force unwrap an Optional value. An Optional type is a regular type, e.g. String, which can also be nil and is written String?. If you have a value of type String? and you want to unwrap it to get a value of type String then you use !on the value. In other words, if x: String? you can write x! to get the plain String value wrapped up by the optional. This only works if you know the value is not nil, otherwise you will get a runtime exception. The ! is to signify the potential danger.  –  rokob   Sep 30 at 5:06