'return *this' 在 C++ 中是什么意思？
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What does 'return *this' mean in C++?
提问by Kloar
I'm converting a C++ program to C#, but this part has me confused. What does return *this mean?
我正在将 C++ 程序转换为 C#，但这部分让我感到困惑。return *this 是什么意思？
template< EDemoCommands msgType, typename PB_OBJECT_TYPE >
class CDemoMessagePB : public IDemoMessage, public PB_OBJECT_TYPE
{
(...)
virtual ::google::protobuf::Message& GetProtoMsg() { return *this; }
}
How would it translate into C#?
它将如何转换为 C#？
回答by Rahul Tripathi
thismeans pointer to the object, so *thisis an object. So you are returning an object ie, *thisreturns a reference to the object.
this表示指向对象的指针，对象*this也是。所以你正在返回一个对象，即*this返回对该对象的引用。
回答by Stephen Brooks
Watch out that if you try to use return *this;on a function whose return type is Typeand not Type&, C++ will try to make a copy of the object and then immediately call the destructor, usually not the intended behaviour. So the return type should be a reference as in your example.
请注意，如果您尝试return *this;在返回类型为Type和 不是的函数上使用Type&，C++ 将尝试制作该对象的副本，然后立即调用析构函数，通常不是预期的行为。所以返回类型应该是你的例子中的引用。
回答by Lake
In your particular case, you are returning the reference to 'this', since the return type of the function is a reference (&).
在您的特定情况下，您将返回对“this”的引用，因为函数的返回类型是引用（&）。
Speaking of the size of returned memory, it is the same as
说到返回内存的大小，和
virtual ::google::protobuf::Message* GetProtoMsg() { return this; }
But the usage at call time differs.
但是通话时的用法不同。
At call time, you will call store the return value of the function by something like:
在调用时，您将通过以下方式调用 store 函数的返回值：
Message& m = GetProtoMsg();
回答by Joseph Pla
You are just returning a reference to the object. thisis a pointer and you are dereferencing it.
您只是返回对对象的引用。this是一个指针，您正在取消引用它。
It translates to C# return this;in the case that you are not dealing with a primitive.
return this;如果您不处理原语，它会转换为 C# 。
回答by Ehsan
Using a pointer we can directly access the value stored in the variable which it points to. To do this, we simply have to precede the pointer's identifier with an asterisk (*), which acts as dereferenceoperator and that can be literally translated to "value pointed by".
使用指针，我们可以直接访问存储在它指向的变量中的值。要做到这一点，我们只需在指针的标识符前面加上一个星号 (*)，它充当dereference运算符，可以直接翻译为“指向的值”。
回答by bash.d
Like in C# thisis an implicit pointer to the object you are currently using.
In your particular case, as you return a reference &to the object, you must use *thisif you want to return the object you are currently working on.
Don't forget that a reference takes the variable itself, or in case of a pointer (this), the object pointed to (*this), but not the pointer (this).
就像在 C# 中一样，this是指向您当前使用的对象的隐式指针。
在您的特定情况下，当您返回&对对象的引用时，*this如果要返回当前正在处理的对象，则必须使用。
不要忘记引用采用变量本身，或者在指针 ( this) 的情况下，是指向 ( ) 的对象*this，而不是指针 ( this)。
