标签:const calls object dynamic constructor Thing vs new using
Calling constructors in c++ without new - Stack Overflow
Q:
I've often seen that people create objects in C++ using
Thing myThing("asdf");
Instead of this:
Thing myThing = Thing("asdf");
This seems to work (using gcc), at least as long as there are no templates involved. My question now, is the first line correct and if so should I use it?
Ans:
1.
Both lines are in fact correct but do subtly different things.
The first line creates a new object on the stack by calling a constructor of the format Thing(const char*)
.
The second one is a bit more complex. It essentially does the following
- Create an object of type
Thing
using the constructorThing(const char*)
- Create an object of type
Thing
using the constructorThing(const Thing&)
- Call
~Thing()
on the object created in step #1
2.
I assume with the second line you actually mean:
Thing *thing = new Thing("uiae");
which would be the standard way of creating new dynamic objects (necessary for dynamic binding and polymorphism) and storing their address to a pointer. Your code does what JaredPar described, namely creating two objects (one passed a const char*
, the other passed a const Thing&
), and then calling the destructor (~Thing()
) on the first object (the const char*
one).
By contrast, this:
Thing thing("uiae");
creates a static object which is destroyed automatically upon exiting the current scope.
标签:const,calls,object,dynamic,constructor,Thing,vs,new,using 来源: https://blog.csdn.net/maxzcl/article/details/122688599
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