初始化类C ++中的引用成员 [英] Initialize reference member in class C++

问题描述

我在一个类中有一个参考成员，如下所示：

I have a class in which I have a reference member as follows:

SampleClass.h

class SampleClass{
public:
SampleClass(bool mirror=false);
void updateFunction(); 
private:
BodyTrackeDevice _device;
BodyBlob& _userBody;
BodyMuscle _muscle;
bool _mirror;
};

SampleClass.cpp

SampleClass::SampleClass(bool mirror)
{
this->_mirror = mirror;
}

错误： SampleClass 必须显式初始化引用成员 _userBody

Error: Constructor for SampleClass must explicitly initialize the reference member _userBody

这很明显，因为我应该做的初始化引用成员的操作应该是

which is obvious because what I should have done to initialise the reference member should have been

SampleClass::SampleClass(bool mirror, BodyBlob& bodyBlob) : _userBody(bodyBlob){
...
}

但是， BodyBlob& 是我从 BodyTrackerDevice 中得到的，作为 BodyTrackerDevice.getTrackedBody [0] 并不是我可以传递给类的构造函数的东西。

However, BodyBlob& is something that I'll be getting from BodyTrackerDevice as BodyTrackerDevice.getTrackedBody[0] and is not something that I can pass to the constructor of the class. What is the right approach followed here to get rid of the error?

推荐答案

引用基本上就像指针，但有两个非常重要的地方，那就是正确的方法来消除错误？区别：a）它们必须在创建时进行初始化（以最大程度地减少与悬挂指针相比悬挂参考的可能性），以及b）无法更改它们指向的对象。

References are basically like pointers, but with two very important difference: a) they must be initialized when created (in order to minimize the possibility of having a dangling references in contrast to a dangling pointer), and b) cannot change the object they point to.

在您的代码中，您有b）可能满足的需求，但对于a）没有（您说您将获得_userBody稍后的值，而不是在构建对象），因此只剩下两种可能性：使用简单的对象（可以通过复制新值进行初始化）[不是很好]，或者仅使用指针而不是引用。

In your code, you have the needs that maybe can be covered by b), but not for a)(you say you'll get the value for _userBody "later", not in the time of building the object), so the you've only two possibilities left: use a simple object (which you can initialize by copying the new value) [not very good], or just use a pointer instead of a reference.

class SampleClass {
public:
    SampleClass(bool mirror=false);
    void updateFunction(); 
private:
    BodyTrackeDevice _device;
    BodyBlob * _userBody;
    BodyMuscle _muscle;
    bool _mirror;
};

SampleClass::SampleClass(bool mirror)
{
    this->_mirror = mirror;
}

void SampleClass::updateFunction()
{
    _userBody = &( device.getTrackedBody[ 0 ] );
}

希望这会有所帮助。

这篇关于初始化类C ++中的引用成员的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！