What does a colon following a C++ constructor name do? [duplicate]

This is a member initializer list, and is part of the constructor’s implementation. The constructor’s signature is: MyClass(); This means that the constructor can be called with no parameters. This makes it a default constructor, i.e., one which will be called by default when you write MyClass someObject;. The part : m_classID(-1), m_userdata(0) is called … Read more

Does a const reference class member prolong the life of a temporary?

Only local const references prolong the lifespan. The standard specifies such behavior in §8.5.3/5, [dcl.init.ref], the section on initializers of reference declarations. The reference in your example is bound to the constructor’s argument n, and becomes invalid when the object n is bound to goes out of scope. The lifetime extension is not transitive through … Read more

What is this weird colon-member (” : “) syntax in the constructor?

Foo(int num): bar(num) This construct is called a Member Initializer List in C++. Simply said, it initializes your member bar to a value num. What is the difference between Initializing and Assignment inside a constructor? Member Initialization: Foo(int num): bar(num) {}; Member Assignment: Foo(int num) { bar = num; } There is a significant difference … Read more