objective c - Swift nil values behaviour -

can send messages nil in swift same way can in objective-c without causing crash?

i tried looking documentation , couldn't find relating this.

not exactly, have use optional chaining. in swift, instance can nil if declared "optional" type. looks this:

var optionalstring : string?

notice ? after string makes possible nil

you cannot call method on variable unless first "unwrap" it, unless use aforementioned optional chaining.

with optional chaining can call multiple methods deep, allow nil value returned:

var optionalresult = optionalstring.method1()?.method2()?.method3()

optionalresult can nil. if of methods in chain return nil, methods after not called, instead optionalresult gets set nil.

you cannot deal directly optional value until explicitly handle case nil. can in 1 of 2 ways:

force unwrap blindly

println(optionalstring!)

this throw runtime error if nil, should sure not nil

you can using simple if statement:

if optionalstring {     println(optionalstring!) } else {     // nil }

or can assign scoped variable don't have forcefully unwrap it:

if let nonoptionalstring = optionalstring {     println(nonoptionalstring) } else {    // nil }