What to do if you don't want a default constructor?
The blog post discusses the implications of not having a default constructor in C++, highlighting design considerations and technical challenges. Solutions like dummy values, std::optional, and std::variant are proposed to address initialization issues.
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In the blog post "What to do if you don't want a default constructor?" by Sandor Dargo, the author discusses the implications of not having a default constructor in C++. The article explores the concept of default constructors, their necessity from a design perspective, and the technical challenges that arise when they are absent. The author provides examples illustrating difficulties in using standard library types like std::vector or std::map without a default constructor. Various solutions are proposed, such as defining a default constructor with dummy values, using std::optional to wrap objects, or employing std::variant for more complex scenarios. The post emphasizes the importance of considering object initialization and invalid states when designing classes without default constructors. Overall, the article offers insights into handling situations where default constructors are not desired in C++ programming.
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6 commentsWhat this means in practice is one never is presented with an uninitialized or partially initialized struct. A non-default constructor gets handed a default initialized struct to start with. This makes for more reliable software. (Double initialization can be removed by the optimizer.)
Why D doesn't have default constructors gets brought up now and then, as it is an unusual choice.
Personally, I like the simplicity of this kind of approach, but prefer to force consumers of the type to be more explicit. To that end, I really like having an constexpr bool operator! instead, so the same checks can be performed without making it easy to accidentally coerce your type into some shady arithmetic operations. You still can if you meant to, but it will be more obvious what you're doing and won't happen accidentally
https://en.cppreference.com/w/cpp/language/operator_comparis...
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