人们为什么编写返回非常量引用的私有字段获取器? [英] Why do people write private-field getters returning a non-const reference?
问题描述
我们都可以同意公共变量不利于封装等等。但是,我注意到有很多代码可以执行此类操作:
class foo {
private:
int integer_;
字符串someString_;
//其他变量
public:
int& integer(){return integer_; }
string& someString(){return someString_; }
//其他函数
}
int main(){
foo f;
f.integer()= 10;
f.someString()=东西;
返回0;
}
我已经看到它在很多地方都在使用,我不知道为什么。基本上,它返回对数据的引用,从而将其直接暴露给外部。所以封装并没有真正实现,从任何角度都没有。
为什么通常使用这种封装?
有一个反复出现的口头禅,即应该使用 getter / setter 函数封装数据。因此,许多(没有经验的或咖啡超负荷的)程序员都会想到他们应该使用类似的东西:
int& integer(){return integer_; }
,但这与简单编写没有太大区别:
class foo {
public://<<<
int integer_;
字符串someString_;
// ...
};
嗯,它添加了一个函数调用,但是您无法控制客户端对引用的操作。 / p>
如果您真的想提供 getter 函数,请输入:
const int& integer()const {return integer_; }
相应的 setter 函数如下:
void整数(const int& value){
integer_ = value;
}
We can all agree on public variables being bad for encapsulation and all that. However, I noticed a lot of code that does this type of stuff:
class foo {
private:
int integer_;
string someString_;
// other variables
public:
int& integer() { return integer_; }
string& someString() { return someString_; }
// other "functions"
}
int main() {
foo f;
f.integer() = 10;
f.someString() = "something";
return 0;
}
I have seen this being used in many places and I don't get why. Basically it returns a reference to the data and thus exposes it directly to the outside. So encapsulation is not really achieved, not from any perspective.
Why is this commonly used?
There's a recurring mantra, that getter/setter functions should be used to encapsulate your data. Hence many (unexperienced or coffee-overloaded) programmers get the idea they should use something like:
int& integer() { return integer_; }
but that isn't much different from simply writing:
class foo {
public: // <<<
int integer_;
string someString_;
// ...
};
Well, it adds a function call, but you cannot control what the client does with the reference.
If you really want to provide a getter function write:
const int& integer() const { return integer_; }
A corresponding setter function looks like:
void integer(const int& value) {
integer_ = value;
}
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