Hands-On Design Patterns with Swift

Using NS_ASSUME_NON_NULL_BEGIN and NS_ASSSUME_NON_NULL_END

We can use NS_ASSUME_NON_NULL_BEGIN and NS_ASSUME_NON_NULL_END in order to express broadly that all properties, method arguments, and return types are non-optional:

NS_ASSUME_NONNULL_BEGIN@interface AnObject: NSObject- (NSString *)sayHello; // return @”Hello World”- (NSString *)append:(NSString *)aString with:(NSString *)anotherString;@endNS_ASSUME_NONNULL_END

The following snippet shows how to use it in Swift:

// Swift 5let object = AnObject()let string = object.sayHello() // Stringlet returnValue = object.append("First String", with: "Next String")let otherString = string.appending(" From Swift") // safe to useassert(otherString == "Hello World From Swift")

As you can see, nothing ...