在 C++ 中初始化之前声明一个对象

2022-01-04 00:00:00 instantiation scope c++ declaration

是否可以在不实例化的情况下在 C++ 中声明变量?我想做这样的事情:

Is it possible to declare a variable in c++ without instantiating it? I want to do something like this:

Animal a;
if( happyDay() ) 
    a( "puppies" ); //constructor call
else
    a( "toads" );

基本上，我只想在条件之外声明一个，以便它获得正确的范围.

Basially, I just want to declare a outside of the conditional so it gets the right scope.

有没有办法在不使用指针和在堆上分配 a 的情况下做到这一点?也许有一些巧妙的参考资料?

Is there any way to do this without using pointers and allocating a on the heap? Maybe something clever with references?

推荐答案

您不能直接在 C++ 中执行此操作，因为对象是在使用默认构造函数定义时构造的.

You can't do this directly in C++ since the object is constructed when you define it with the default constructor.

但是，您可以首先运行参数化构造函数:

You could, however, run a parameterized constructor to begin with:

Animal a(getAppropriateString());

或者您实际上可以使用诸如 ?: 运算符 之类的东西来确定正确的字符串.(更新:@Greg 为此提供了语法.请参阅该答案)

Or you could actually use something like the ?: operator to determine the correct string. (Update: @Greg gave the syntax for this. See that answer)

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