optional-variables

The ! mark is used for the optional value in Swift to extract the wrapped value of it, but the value can be extracted without the ! : var optionalString: String? = "optionalString" println(optionalString) another example using the ! : var optionalString: String? = "optionalString" println(optionalString!) both the codes above get the right value, so I wonder what's the difference between using and not using ! , is it just for detect an error at runtime if the optional value is nil or something else? Thanks in advance. As others have already stated, a really good place to start would be with

What does the following mean? Class.Function(variable := 1 + 1) What is this operator called, and what does it do? It is used to assign optional variables, without assigning the previous ones. sub test(optional a as string = "", optional b as string = "") msgbox(a & b) end sub you can now do test(b:= "blaat") 'in stead of test("", "blaat") It assigns the optional parameter "variable" the value 2. VB.NET supports this syntax for named (optional) parameters in method calls. This particular syntax informs Class.Function that its parameter variable is to be set to 2 (1 + 1). 来源： https:/

I have some quite simple doubt regarding optional binding,global variable & wrapping and unwrapping . Since I am new to SWIFT, its very important to understand the tits & bits of their concepts. 1) In Swift if I declare a global variable, I have 2 options either to make it optional or non optional, so let I am having 2-4 or more optional variables . So is it advisable to optional bind all those variables in viewDidLoad() method// so that I could use them without any problem of unwrapping and fatal error in my program. 2) Let me make myself more clear by the following example- I have 2 VC in my

Given the following in Swift: var optionalString: String? let dict = NSDictionary() What is the practical difference between the following two statements: optionalString = dict.objectForKey("SomeKey") as? String vs optionalString = dict.objectForKey("SomeKey") as! String? The practical difference is this: var optionalString = dict["SomeKey"] as? String optionalString will be a variable of type String? . If the underlying type is something other than a String this will harmlessly just assign nil to the optional. var optionalString = dict["SomeKey"] as! String? This says, I know this thing is a