C++ 'function style' class initialization [duplicate]

Question

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Is there a difference between copy initialization and direct initialization? (9 answers)

Closed 9 years ago.

Suppose I have a class Foo. I can imagine two ways of initialization: (i.e., invoking the constructor)

Foo myFooLong = Foo(...args...);
Foo myFooShort(...args...);

Is there any difference in operation (as far as I'm concerned, that's not the case)?

Answer 1

The statement

  Foo myFooLong = Foo(...args...);

first creates a Foo object (the right side) and then copies it to the left operand using the copy construtor.

The second statement just creates a new Foo object.

There is no reason to prefer the first approach over the second. The first one involves unnecessary temporary creation and copying hence needs an accessible copy constructor ( copy elision may be applied).