英文:
Error when declaring an array without specifying size initially: <error-type> Crew::flightAttendants Incomplete type is not allowed
问题
给定这个**C++**类...
//C++代码
class Crew {
Person flightAttendants[]; //错误: <error-type> Crew::flightAttendants 不允许不完整的类型。
Person captain, firstOfficer;
public:
Crew(Person, Person, Person);
};
我想声明（但不要在一开始初始化）flightAttendants[] 数组，而不需要事先指定它的长度（我只想在之后指定其大小）。就像Java一样，例如，我们可以这样做：
//JAVA代码
class Lamp {
private int nLightBulbs;
private boolean lightBulbs[];
Lamp(int nLightBulbs) {
this.nLightBulbs = nLightBulbs;
this.lightBulbs = new boolean[nLightBulbs];
}
}
这就是问题。
英文:
So given this class in C++...
//C++ CODE
class Crew {
Person flightAttendants[]; //Error: <error-type> Crew::flightAttendants Incomplete type is not allowed.
Person captain, firstOfficer;
public:
Crew(Person, Person, Person);
};
I'd like to declare (but NOT at first initialize) the flightAttendants[] array without specifying what would be it's length beforehand (I just want to specify its size after). Just like Java, for example, in which we could do:
//JAVA CODE
class Lamp {
private int nLightBulbs;
private boolean lightBulbs[];
Lamp(int nLightBulbs) {
this.nLightBulbs = nLightBulbs;
this.lightBulbs = new boolean[nLightBulbs];
}
}
That's the question.
答案1
得分: 3
Person flightAttendants[];
你想要的例子是：
Person * flightAttendants;
然后就像在Java中一样：
this.lightBulbs = new boolean[nLightBulbs];
在C++中执行：
flightAttendants = new Person[...预期大小...];
但更实际的做法是使用std::vector
std::vector<Person> flightAttendants;
出于许多原因，包括能够获取其大小/调整大小以及不必管理Person * flightAttendants中使用的指针（即使还有其他安全方式来管理它）
请注意，在Java中，您始终操作实例的指针，在C++中，我们可以选择，而先前的数组/向量不会记住Person实例的指针，而是Person的实例。
英文:
> Person flightAttendants[];
you wanted for instance
Person * flightAttendants;
then like in Java you have :
> this.lightBulbs = new boolean[nLightBulbs];
in C++ do
flightAttendants = new Person[...expected size...];
But it is very more practical to use a std::vector
std::vector<Person> flightAttendants;
for a lot of reasons including to be able to get its size/to resize it, and to not have to manage the pointer used in Person * flightAttendants (even there are other ways to manage it in a secure way)
Note in Java you always manipulate pointer to instances, in C++ we have the choice and the previous array/vector do not memorize pointer to instances of Person but instances of Person
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