DispatchQueue
public extension DispatchQueue
-
Executes a block of code, associated with a unique token, only once. The code is thread safe and will only execute the code once even in the presence of multithreaded calls.
Declaration
Swift
class func once(token: String, block: () -> Void)
Parameters
token
A unique reverse DNS style name such as com.vectorform.
or a GUID. block
The block to execute once.