bool is often used to implement an enum with two values. But when used carelessly, this leads to error-prone code. While
it may seem reasonable when defining a boolean function parameter, the meaning might not be so clear at the function call point.
If the function only has a single boolean argument, the potential ambiguity is mitigated: the function name can indicate its purpose, and what
true and false mean. But when a function has more than one boolean argument, it becomes increasingly difficult to come up
with descriptive names. Moreover, it becomes very easy for callers to inadvertently swap the argument order. In such cases, it is much clearer to use
an explicit enum or, if the boolean has a logical relation to another argument, to package them together in a struct, where
the data member name can give meaning to the boolean. Another option is to split dealing with the multiple boolean arguments into multiple functions
because sometimes multiple boolean parameters indicate a function that’s trying to do too much.
Noncompliant code example
class Image;
Image* loadImage(const char *path, bool bw, bool lowRes, bool createEmptyIfNotExist); // Noncompliant
bool saveImage(const Image *image, const char *path, bool color, bool highRes); // Noncompliant
void f(const char* path) {
Image *image = loadImage(path, false, true, false);
// do some processing on image
saveImage(image, path, true, false);
}
Compliant solution
class Image;
enum class ColorMode {RGB, BlackAndWhite};
enum class Resolution {Full, Low};
enum class NotExistFallback {CreateEmpty, ReturnNullPtr};
Image* loadImage(const char *path, ColorMode mode, Resolution res, NotExistFallback fallback);
bool saveImage(const Image *image, const char *path, ColorMode mode, Resolution res);
void f(const char* path) {
Image *image = loadImage(path, ColorMode::RGB, Resolution::Low, NotExistFallback::ReturnNullPtr);
// do some processing on image
saveImage(image, path, ColorMode::RGB, Resolution::Low);
}
