Criticism
This pattern should be used carefully as it can make errors/bugs appear as normal program execution.
Care should be taken not to implement this pattern just to void null checks and make code more readable, since the harder to read code may just move to another place and be less standard - such as when different logic must execute in case the object provided is indeed the Null Object. For the common pattern in most languages with reference types is to compare a reference to a single value referred to as null or nil. Also, there is additional need for testing that no code anywhere ever assigns null instead of the Null Object, because in most cases and languages with static typing, this is not a compiler error if the Null Object is of a reference type, although it would certainly lead to errors at run time in parts of the code where the pattern was used to avoid null checks. On top of that, in most languages and assuming there can be many Null Objects (i.e. the Null Object is a reference type but doesn't implement the Singleton pattern in one or another way), checking for the Null Object instead of for the null or nil value introduces overhead, as does the singleton pattern likely itself upon obtaining the singleton reference.
Read more about this topic: Null Object Pattern
Famous quotes containing the word criticism:
“A friend of mine spoke of books that are dedicated like this: “To my wife, by whose helpful criticism ...” and so on. He said the dedication should really read: “To my wife. If it had not been for her continual criticism and persistent nagging doubt as to my ability, this book would have appeared in Harper’s instead of The Hardware Age.””
—Brenda Ueland (1891–1985)
“The greater the decrease in the social significance of an art form, the sharper the distinction between criticism and enjoyment by the public. The conventional is uncritically enjoyed, and the truly new is criticized with aversion.”
—Walter Benjamin (1892–1940)
“Cubism had been an analysis of the object and an attempt to put it before us in its totality; both as analysis and as synthesis, it was a criticism of appearance. Surrealism transmuted the object, and suddenly a canvas became an apparition: a new figuration, a real transfiguration.”
—Octavio Paz (b. 1914)