Constructor Design
Constructors run when an instance of a type is created.
Constructors that don’t take any parameters are called default constructors.
Constructors are the most natural way to create instances of a type. Most developers will search and try to use a constructor before they consider alternative ways of creating instances (such as factory methods).
✔️ CONSIDER providing simple, ideally default, constructors.
A simple constructor has a very small number of parameters, and all parameters are primitives or enums. Such simple constructors increase usability of the framework.
✔️ CONSIDER using a static factory method instead of a constructor if the semantics of the desired operation do not map directly to the construction of a new instance, or if following the constructor design guidelines feels unnatural.
✔️ DO use constructor parameters as shortcuts for setting main properties.
✔️ DO minimal work in the constructor.
Constructors should not do much work other than capture the constructor parameters. The cost of any other processing should be delayed until required.
✔️ DO throw exceptions from instance constructors, if appropriate.
✔️ DO explicitly declare the public default constructor in classes, if such a constructor is required.
If you don’t explicitly declare any constructors on a type, C++ language will automatically add a public default constructor.
Adding a parameterized constructor to a class prevents the compiler from adding the default constructor. This often causes accidental breaking changes.
❌ AVOID calling virtual members on an object inside its constructor. Calling a virtual member is not supported by C++.
See also