如果构造函数可用于初始化... [英] if Constructor can be used to initialize ...
问题描述
如果可以使用构造函数进行初始化，何时分配内存
/说新运营商等？
谢谢
If a Constructor can be used to initialize, when is memory is allocated
/ say the "new" operator etc?
Thanks
推荐答案
* 2005：
* 2005:
>
如果可以使用构造函数进行初始化，则何时分配内存
/表示new运营商等？
>
If a Constructor can be used to initialize, when is memory is allocated
/ say the "new" operator etc?
在调用构造函数之前的某个时间。
对于new以前的操作员。
-
答：因为它弄乱了人们通常阅读文字的顺序。
问：为什么这么糟糕？
A：热门发布。
问：usenet和电子邮件中最烦人的事情是什么？
Sometime before the constructor is called.
For the "new" operator that''s immediately before.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
这是否意味着如果我们使用构造函数，我们不需要一个new
运算符？
谢谢
Alf P. Steinbach写道：
Does it mean that if we use a constructor, we don''t need a "new"
operator?
Thanks
Alf P. Steinbach wrote:
* 2005：
* 2005:
如果可以使用构造函数进行初始化，则何时分配内存
/表示new运营商等？
If a Constructor can be used to initialize, when is memory is allocated
/ say the "new" operator etc?
在调用构造函数之前的某个时间。
对于new以前的操作员。
-
答：因为它弄乱了人们通常阅读文字的顺序。
问：为什么这么糟糕？
A：热门发布。
问：usenet和电子邮件中最烦人的事情是什么？
Sometime before the constructor is called.
For the "new" operator that''s immediately before.
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
2005写道：
2005 wrote:
如果构造函数可以用于初始化，何时分配内存
/说新运营商等？
谢谢
If a Constructor can be used to initialize, when is memory is allocated
/ say the "new" operator etc?
Thanks
你不需要新的运营商来分配 - 在一个完美的世界里，使用
new应该是不鼓励的。
ctor'的主要目的是根据其类型的
内容分配一个实例（忽略现在继承的类）和任何
资源是必需的。
在C ++中，它恰好具有初始化
成员的次要目的，如果有的话，使用init列表。初始化不是一个
的要求，但经常被忽视并且非常有用。
回答你的问题：当构造函数是$ / $时分配发生b $ b被调用。
和invoke并不意味着打电话。
#include< iostream>
class N
{< br $>
int n;
public：
N（）：n（0）{std :: cout<< invoke ctor\\\
; }
~N（）{std :: cout<< invoke d~tor\ n; }
const int& get（）const {return n; }
};
int main（）
{
N实例; //分配发生在这里
std :: cout<< instance.n = << instance.get（）<< std :: endl;
返回0;
} //释放发生在这里 - 在范围结束时
/ *
调用ctor
instance.n = 0
调用d / tor
* /
解释在常见问题解答中：
http://www.parashift.com/c++-faq-lite/ctors.html
You don''t need the new operator to allocate - in a perfect world, using
new should be discouraged.
A ctor''s primary purpose is to allocate an instance based on the
contents of its type (ignoring inherited classes for now) and whatever
resources are required.
In C++ it happens to have a secondary purpose that is to initialize
members, if any, using an init list. The initialisation is not a
requirement but too often overlooked and quite usefull.
To answer your question: allocation happens when the constructor is
invoked.
and "invoke" does not mean "call".
#include <iostream>
class N
{
int n;
public:
N() : n(0) { std::cout << "invoke ctor\n"; }
~N() { std::cout << "invoke d~tor\n"; }
const int& get() const { return n; }
};
int main()
{
N instance; // allocation happens here
std::cout << "instance.n = " << instance.get() << std::endl;
return 0;
} // deallocation happens here - at end of scope
/*
invoke ctor
instance.n = 0
invoke d~tor
*/
The explanation is in the FAQ:
http://www.parashift.com/c++-faq-lite/ctors.html
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