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:
“Unless criticism refuses to take itself quite so seriously or at least to permit its readers not to, it will inevitably continue to reflect the finicky canons of the genteel tradition and the depressing pieties of the Culture Religion of Modernism.”
—Leslie Fiedler (b. 1917)
“It is ... pathetic to observe the complete lack of imagination on the part of certain employers and men and women of the upper-income levels, equally devoid of experience, equally glib with their criticism ... directed against workers, labor leaders, and other villains and personal devils who are the objects of their dart-throwing. Who doesn’t know the wealthy woman who fulminates against the “idle” workers who just won’t get out and hunt jobs?”
—Mary Barnett Gilson (1877–?)
“However intense my experience, I am conscious of the presence and criticism of a part of me, which, as it were, is not a part of me, but a spectator, sharing no experience, but taking note of it, and that is no more I than it is you. When the play, it may be the tragedy, of life is over, the spectator goes his way. It was a kind of fiction, a work of the imagination only, so far as he was concerned.”
—Henry David Thoreau (1817–1862)