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In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object.It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.
Encapsulate creating and assembling the parts of a complex object in a separate Builder object. A class delegates object creation to a Builder object instead of creating the objects directly. A class (the same construction process) can delegate to different Builder objects to create different representations of a complex object.
When a class constructor does not explicitly call the constructor of one of its object-valued fields in its initializer list, the default constructor for the field's class is called. In the standard library, certain containers "fill in" values using the default constructor when the value is not given explicitly.
Copy constructors are the standard way of copying objects in C++, as opposed to cloning, and have C++-specific nuances. The first argument of such a constructor is a reference to an object of the same type as is being constructed (const or non-const), which might be followed by parameters of any type (all having default values).
When an object is created, a pointer to this table, called the virtual table pointer, vpointer or VPTR, is added as a hidden member of this object. As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table.
An IDL file is compiled via the MIDL compiler. For use with C/C++, the MIDL compiler generates a header file with struct definitions to match the vtbls of the declared interfaces and a C file containing declarations of the interface GUIDs. C++ source code for a proxy module can also be generated by the MIDL compiler.
A C++03 compiler has no way of knowing if get_five() actually is constant at runtime. In theory, this function could affect a global variable, call other non-runtime constant functions, etc. C++11 introduced the keyword constexpr, which allows the user to guarantee that a function or object constructor is a compile-time constant. [11]
Objects can contain other objects in their instance variables; this is known as object composition. For example, an object in the Employee class might contain (either directly or through a pointer) an object in the Address class, in addition to its own instance variables like "first_name" and "position".