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工作学习 / IT技术讨论 / Can I write constructer as private in c++, if I can who can access it ?
(This my interview question, continue)
-guest:;
2001-7-3
(#118794@0)
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yes, you can. And you could only new an object in this case.
-mrviceroy(杀人者Daniel是也);
2001-7-4
(#119353@0)
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what the side effect for the virtual function in class?
-guest:interview question;
2001-7-4
(#119468@0)
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the only side effect I know of is that if you declare a virtual function , the calss size will be increased(probably by 4) , because the compiler has to insert a virtual table pointer in the class.
-numnum(numnum);
2001-7-5
(#120563@0)
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u wrong, if the constructor is private, new can't create its instance.constructor be private is meanful, friend function/class can create it. that's the way to avoid others(ur lib user) create the instance of class which you think they shouldn't do so.
-blaise(blaise);
2001-7-4
{184}
(#119686@0)
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yeah, in addition, the class itself can call this private constructor too, it's useful when you declare a static member of the class itself.
-numnum(numnum);
2001-7-5
(#120567@0)
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numnum is rightYou can create only ONE instance of the class by using private constructor. And in Design Patten, this is called Singleton Class.
-frank2001(mouse);
2001-7-6
{129}
(#122877@0)
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You can create a number of instances of the class which has only private constructor(s).
-old(HH);
2001-7-15
(#132969@0)
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I don't think so. How to create the first one if you have only private constructor(s)?
-loafer(loafer);
2001-7-16
(#133425@0)
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Change the private static Singleton obj in the class declaration to static Singleton obj[3], then 3 objects can be created.
-old(HH);
2001-7-16
(#133481@0)
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what can you do with such a class? it only can be used as an encapsulated static functions set working on static members. In fact, it's not like a class, just a period of static codes, no, only some constants.. Private construtor is very useful when you want to transfer class object as a parameter
-loafer(loafer);
2001-7-16
{89}
(#133513@0)
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It can be used to limit the number of instances of a singleton class to be created. For example “your” singleton class can has only one instance, “my” singleton class can has a fixed number of instances.class Singleton {
public:
/* Other public members will be added here */
private:
/* Other private members will be added here */
static Singleton obj[3];
};
-old(HH);
2001-7-16
{163}
(#133531@0)
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still i can't understand how to use it without any public constructor. You can only use the static members. what's the purpose with such kind of classes?
-loafer(loafer);
2001-7-16
(#134038@0)
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把你的class girl增加一个这样的构造函数，然后跟踪一下boy::suit，你就清楚了。哈哈，我就看了两条Post，都有你。看来你是这里的常客。我用朋友的UserID上来的，回头我也注册一个。
-babyface(Tracy);
2001-7-15
(#133076@0)
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自己拷贝自己的时候用
-babyface(Tracy);
2001-7-15
(#133078@0)
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is the singleton pattern
-guest:;
2001-7-17
(#135368@0)