问题
What is an Anonymous Object exactly?
Does C++ support/have Anonymous Objects?
回答1:
The C++ standard does not define the term "anonymous object", but it stands to reason that one might sanely use the term to describe any object that has no name:
- Temporaries:
f(T()); - Unnamed function parameters:
void func(int, int, int);
What I wouldn't count is dynamically-allocated objects:
Technically speaking, an "object" is any region of storage [1.8/1 in 2003], which would include the X bytes making up the integer dynamically-allocated by new int;.
In int* ptr = new int; the pointer (itself an object too, don't forget!) has the name ptr and the integer itself has no name other than *ptr. Still, I'd hesitate to call this an anonymous object.
Again, though, there's no standard terminology.
回答2:
This is a simplistic answer, but an anonymous object is basically an object which the compiler creates a class for.
For example in C# (I know this is kinda irrelevant) you can just create an anonymous type by doing:
new { filename = value }.
The compiler effectively creates a class called AnonSomething1 [A random name you don't know] which has those fields. Therefore at that point you just created an instance of that AnonSomething1. C++ does not allow you to make anonymous class types inline (like Java and C# which have a base Object class which the anon types can derive).
However you can make an anonymous struct by simply writing
struct {
int field1;
std::string field2;
} myanonstruct;
which creates an anonymous struct and instantiates it with the alias myanonstruct. This C++ code does not define a type, it just creates an anonymous one with 1 instance.
See C#: Anon Types
See Java: Anon Types
See C++ Structs: msdn
来源：https://stackoverflow.com/questions/5330287/what-is-an-anonymous-object