Code snippet below demonstrate how optional binding works.Code will fail gracefully when try to access optional variable with nil value, no runtime error will be triggered.In this section, we will look into the basic concept and ways we can use to access value of optional type, mainly optional binding and forced unwrapping. The best example of implicitly unwrapped optional type are the IBOutlets you created for your view controller. ![]() Set variables as implicitly unwrapped optional type only when you are not able to initialize the variables during its class or struct initialization, but you are confident that the variables will not be nil for its entire lifetime after being initialized. Avoid using implicitly unwrapped optional type as it might cause a runtime error. ![]() Use the form unless you're very sure that the cast is valid, in which case you can drop it to avoid dealing with the unnecessary optional. Set variables as optional type only when you are not able to initialize the variables during its class or struct initialization, or the variables might become nil at some point of its lifetime after being initialized. 1 Answer Sorted by: 3 With 'as' if the object can't be cast, then it returns nil, while with 'as', if the object can't be cast than it crashes.Always declare variables as non-optional type. If you believe that this is the case, you can perform downcasting on the subclass type using the type cast operator (as or as).If myVariable is nil and it is being access without using optional binding, runtime error will trigger.Value of myVariable can be accessed with or without using optional binding.The latest update in Swift addresses a small but potentially frustrating inconsistency that could occur. What is the best practice for casting between the different number types Types float, double, int are the ones I use the most in C++. Declare myVariable as implicitly unwrapped optional MyType. New Support for Collection Downcasts in Cast Patterns.(more on optional binding and forced unwrapping later) When I try to downcast an element of a dictionary, I get a syntax error: let adDict:Dictionary< String, AnyObject> (indexPath. Value of myVariable can only be accessed by using optional binding or forced unwrapping.myVariable can be nil at some point of its lifetime.As cast from Any to UIAccessibilityIdentification protocol is failed due to this bug in Swift so you first need to downcast to a known type that falls in the above list to cast as UIAccessibilityIdentification. myVariable will not be nil for its entire lifetime. You can check the list of UI elements here that conforms to UIAccessibilityIdentification. ![]()
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