允许将一个类转换为bool？ [英] Allowing a class to be converted to bool?
问题描述
是否可以允许将一个类转换为bool？
例如，如果我有：
class foo {
私人：
未签名我;
};
我想评估：
if（foo）
通过查看foo.i，我该怎么做？
谢谢
Joseph
Joseph Turian写道：是否可以允许课程转换为bool？
例如，如果我有：
class foo {
私人：
未签名我;
};
<我要评估：
if（foo）
通过查看foo.i，我该怎么做？
使用转换操作符...
class foo
{
public：
operator bool （）
{
返回i！= 0;
}
.....
Joseph Turian写道：是否可以允许将一个类转换为bool？
例如，如果我有：
class foo {
private：
未签名我;
};
我想评估：
if（foo）
通过查看foo.i，我该怎么做？
class foo
{
public：
operator bool（）const
{
返回i！= 0;
}
私人：
未签名i;
};
但是要知道这可以让你的班级被转换：
foo f;
if（f）; //酷
int a = f; // ..也有效
Jonathan
Jonathan Mcdougall写道：
但是要知道这可以让你的班级被转换：
foo f;
if（f）; //酷
int a = f; // ..也有效
好的等等。
我创造了一个类''foo''的全部原因包装POD类型
''unsigned''是因为我想通过创建几个$ f $ b子类型的foo来确保类型安全。
即我希望有三个A，B和C类基本上是
类型''unsigned''。
但是，我想要A ，B和C被认为是不同的类型，并且比如说，B和B类型之间的A和B类型之间的比较导致编译器错误。
所以，这样做，我希望A，B和C继承自foo。
问题1：A，B和C是否继承自foo实现了
在A，B，
和C之间禁止比较和演员的期望效果？
问题2：添加操作员bool转换功能是否打开了我
$ b任何类型转换风险$ b？
谢谢！
Joseph
Is it possible to allow a class to be converted to bool?
For example, if I have:
class foo {
private:
unsigned i;
};
and I want to evaluate:
if (foo)
by looking at foo.i, how can I do that?
Thanks
Joseph
解决方案Joseph Turian wrote:Is it possible to allow a class to be converted to bool?
For example, if I have:
class foo {
private:
unsigned i;
};
and I want to evaluate:
if (foo)
by looking at foo.i, how can I do that?
Use a conversion operator ...
class foo
{
public:
operator bool()
{
return i != 0;
}
.....
Joseph Turian wrote:Is it possible to allow a class to be converted to bool?
For example, if I have:
class foo {
private:
unsigned i;
};
and I want to evaluate:
if (foo)
by looking at foo.i, how can I do that?
class foo
{
public:
operator bool() const
{
return i != 0;
}
private:
unsigned i;
};
But know that this makes it possible for your class to be converted:
foo f;
if (f) ; // cool
int a = f; // .. also works
Jonathan
Jonathan Mcdougall wrote:
But know that this makes it possible for your class to be converted:
foo f;
if (f) ; // cool
int a = f; // .. also works
Okay wait.
The whole reason I created a class ''foo'' which wraps the POD type
''unsigned'' is because I want to ensure type-safety by creating several
sub-types of foo.
i.e. I want to have three classes A, B, and C which are essentially of
type ''unsigned''.
However, I want A, B, and C to be considered distinct types and to
have, say, comparisons between A and B types to cause a compiler error.
So, to do so, I want to have A, B, and C inherit from foo.
Question 1: Does having A, B, and C inherit from foo achieve the
desired effect of disallowing comparisons and casts between types A, B,
and C?
Question 2: Does adding the operator bool conversion function open me
to any type-conversion risks?
Thanks!
Joseph
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