blocks|key|212766|text|这足以声明枚举变量并对其进行比较：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|212767|enum+Days+{Saturday,+Sunday,+Tuesday,+Wednesday,+Thursday,+Friday};
Days+day+=+Saturday;
if+(day+==+Saturday)+{
++++std::cout+<<+"Ok+its+Saturday";
}|code-block|syntax|javascript|212768|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This will be sufficient to declare your enum variable and compare it:

<pre><code>enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};
Days day = Saturday;
if (day == Saturday) {
 std::cout &lt;&lt; "Ok its Saturday";
}
</code></pre>

blocks|key|2860541|text|这其中的大部分应该会给你带来编译错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860542|//+note+the+lower+case+enum+keyword
enum+Days+{+Saturday,+Sunday,+Monday,+Tuesday,+Wednesday,+Thursday,+Friday+};|code-block|syntax|javascript|2860543|现在，Saturday、Sunday等可以用作顶级裸常量，Days可以用作类型：|offset|length|style|CODE|2860544|Days+day+=+Saturday;+++//+Days.Saturday+is+an+error|2860545|类似地，稍后要测试：|2860546|if+(day+==+Saturday)
++++//+...|2860547|这些枚举的值就像赤裸裸的常量-它们没有作用域-通过编译器的一些额外帮助：(除非您正在使用C%2B%2B11枚举类)，它们不像对象或结构成员那样被封装，并且您不能将它们引用为Days的成员。|2860548|通过引入enum+class的C%2B%2B11，您将获得您想要的东西|2860549|enum+class+Days
{
++++SUNDAY,
++++MONDAY,
++++//+...+etc.
}

//+...

if+(day+==+Days::SUNDAY)
++++//+...|2860550|请注意，此C%2B%2B在几个方面与C略有不同，其中之一是C在声明变量时需要使用enum关键字：|2860551|//+day+declaration+in+C:
enum+Days+day+=+Saturday;|2860552|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/C%252B%252B11#Strongly_typed_enumerations^0|0|0|3|8|C|6|T|4|0|0|0|0|2A|4|0|4|A|F|5|0|0|0|10|4|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1C|8|@$I|1D|J|1E|K|L]|$I|1F|J|1G|K|L]|$I|1H|J|1I|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1M|8|@$I|1N|J|1O|K|L]]|9|@]|A|$]]|$1|U|3|V|5|6|7|1P|8|@$I|1Q|J|1R|K|L]]|9|@$I|1S|J|1T|1|1U]]|A|$]]|$1|W|3|X|5|D|7|1V|8|@]|9|@]|A|$E|F]]|$1|Y|3|Z|5|6|7|1W|8|@$I|1X|J|1Y|K|L]]|9|@]|A|$]]|$1|10|3|11|5|D|7|1Z|8|@]|9|@]|A|$E|F]]|$1|12|3|-4|5|6|7|20|8|@]|9|@]|A|$]]]|13|$14|$5|15|16|17|A|$18|19]]]]

Much of this should give you compilation errors. 

<pre><code>// note the lower case enum keyword
enum Days { Saturday, Sunday, Monday, Tuesday, Wednesday, Thursday, Friday };
</code></pre>

Now, <code>Saturday</code>, <code>Sunday</code>, etc. can be used as top-level bare constants,and <code>Days</code> can be used as a type:

<pre><code>Days day = Saturday; // Days.Saturday is an error
</code></pre>

And similarly later, to test:

<pre><code>if (day == Saturday)
 // ...
</code></pre>

These <code>enum</code> values are like bare constants - they're un-scoped - with a little extra help from the compiler: (unless you're using C++11 enum classes) they aren't encapsulated like object or structure members for instance, and you can't refer to them as members of <code>Days</code>.

You'll have what you're looking for with <a href="http://en.wikipedia.org/wiki/C%2B%2B11#Strongly_typed_enumerations" rel="noreferrer">C++11</a>, which introduces an <code>enum class</code>:

<pre><code>enum class Days
{
 SUNDAY,
 MONDAY,
 // ... etc.
}

// ...

if (day == Days::SUNDAY)
 // ...
</code></pre>

Note that this C++ is a little different from C in a couple of ways, one is that C requires the use of the <code>enum</code> keyword when declaring a variable:

<pre><code>// day declaration in C:
enum Days day = Saturday;
</code></pre>

blocks|key|2860582|text|当您声明枚举值时，C%2B%2B中的枚举就像是被您给出的名称所掩盖的整数(这不是一个定义，只是它的工作方式的一个提示)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860583|但是您的代码中有两个错误：|2860584|2860585|+enum+enum|ordered-list-item|offset|length|style|CODE|2860586|您在星期六之前不需要Days.。|2860587|如果此枚举是在类中声明的，则使用拼写|2860588|2860589|entityMap^0|0|0|0|1|4|6|4|0|A|5|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|V|8|@$H|W|I|X|J|K]|$H|Y|I|Z|J|K]]|9|@]|A|$]]|$1|L|3|M|5|G|7|10|8|@$H|11|I|12|J|K]]|9|@]|A|$]]|$1|N|3|O|5|G|7|13|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|R|$]]

Enums in C++ are like integers masked by the names you give them, when you declare your enum-values (this is not a definition only a hint how it works).

But there are two errors in your code:

<ol>
<li>Spell <code>enum</code> all lower case</li>
<li>You don't need the <code>Days.</code> before Saturday.</li>
<li>If this enum is declared in a class, then use
<code>if (day == YourClass::Saturday){}</code></li>
</ol>

blocks|key|3074015|text|遗憾的是，枚举的元素是“全局的”。您可以通过执行day+=+Saturday来访问它们。这意味着你不能使用enum+A+{+a,+b+}+;和enum+B+{+b,+a+}+;，因为它们是冲突的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3074016|entityMap^0|O|E|1H|H|1Z|H|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

Sadly, elements of the enum are 'global'. You access them by doing <code>day = Saturday</code>. That means that you cannot have <code>enum A { a, b } ;</code> and <code>enum B { b, a } ;</code> for they are in conflict.

blocks|key|2860616|text|枚举不是使用一堆if语句，而是很好地使用switch语句|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860617|我在为我的游戏构建的关卡构建器中使用了一些枚举/开关组合。|2860618|编辑:另一件事，我看到你想要类似的语法；|2860619|if(day+==+Days.Saturday)
etc|code-block|syntax|javascript|2860620|您可以在C%2B%2B中执行此操作：|2860621|if(day+==+Days::Saturday)
etc|2860622|下面是一个非常简单的例子：|2860623|EnumAppState.h|2860624|#ifndef+ENUMAPPSTATE_H
#define+ENUMAPPSTATE_H
enum+eAppState
{
++++STARTUP,
++++EDIT,
++++ZONECREATION,
++++SHUTDOWN,
++++NOCHANGE
};
#endif|2860625|Somefile.cpp|2860626|#include+"EnumAppState.h"
eAppState+state+=+eAppState::STARTUP;
switch(state)
{
case+STARTUP:
++++//Do+stuff
++++break;
case+EDIT:
++++//Do+stuff
++++break;
case+ZONECREATION:
++++//Do+stuff
++++break;
case+SHUTDOWN:
++++//Do+stuff
++++break;
case+NOCHANGE:
++++//Do+stuff
++++break;
}|2860627|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|15|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|H|7|18|8|@]|9|@]|A|$I|J]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|H|7|1A|8|@]|9|@]|A|$I|J]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

Rather than using a bunch of if-statements, enums lend themselves well to switch statements

I use some enum/switch combinations in the level builder I am building for my game.

EDIT: Another thing, I see you want syntax similar to;

<pre><code>if(day == Days.Saturday)
etc
</code></pre>

You can do this in C++:

<pre><code>if(day == Days::Saturday)
etc
</code></pre>

Here is a very simple example: 

EnumAppState.h

<pre><code>#ifndef ENUMAPPSTATE_H
#define ENUMAPPSTATE_H
enum eAppState
{
 STARTUP,
 EDIT,
 ZONECREATION,
 SHUTDOWN,
 NOCHANGE
};
#endif
</code></pre>

Somefile.cpp

<pre><code>#include "EnumAppState.h"
eAppState state = eAppState::STARTUP;
switch(state)
{
case STARTUP:
 //Do stuff
 break;
case EDIT:
 //Do stuff
 break;
case ZONECREATION:
 //Do stuff
 break;
case SHUTDOWN:
 //Do stuff
 break;
case NOCHANGE:
 //Do stuff
 break;
}
</code></pre>

blocks|key|2860635|text|首先，在枚举中使用“E”，“e”作为小写。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860636|第二，将类型名称'Days‘放在’Days.周六‘中。|2860637|第三，...buy+yourself+a+good+C%2B%2B书。|2860638|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

First of all, make 'E' in enum, 'e' as a lower case.

Second, drop type name 'Days' in 'Days.Saturday'.

Third ...buy yourself a good C++ book.

blocks|key|2860666|text|这在C%2B%2B中应该不起作用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860667|Days.Saturday|code-block|syntax|javascript|2860668|Days不是包含可以使用点运算符访问的成员的作用域或对象。这种语法只是一种C#风格，在C%2B%2B中是不合法的。|2860669|微软长期以来一直在维护一个C%2B%2B扩展，它允许您使用范围操作符访问标识符：|2860670|enum+E+{+A,+B,+C+};

A;
E::B;+//+works+with+Microsoft's+extension|2860671|在C%2B%2B03中，在枚举中声明的标识符只存在于与枚举类型本身相同的作用域中。|2860672|A;
E::B;+//+error+in+C%2B%2B03|2860673|C%2B%2B11使得使用枚举名称限定枚举标识符是合法的，并且还引入了枚举类，这些类为标识符创建了一个新的作用域，而不是将它们放在周围的作用域中。|2860674|A;
E::B;+//+legal+in+C%2B%2B11

enum+class+F+{+A,+B,+C+};

A;+//+error
F::B;|2860675|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

This should not work in C++:

<pre><code>Days.Saturday
</code></pre>

Days is not a scope or object that contains members you can access with the dot operator. This syntax is just a C#-ism and is not legal in C++.

Microsoft has long maintained a C++ extension that allows you to access the identifiers using the scope operator:

<pre><code>enum E { A, B, C };

A;
E::B; // works with Microsoft's extension
</code></pre>

But this is non-standard before C++11. In C++03 the identifiers declared in an enum exist only in the same scope as the enum type itself.

<pre><code>A;
E::B; // error in C++03
</code></pre>

C++11 makes it legal to qualify enum identifiers with the enum name, and also introduces enum classes, which create a new scope for the identifiers instead of placing them in the surrounding scope.

<pre><code>A;
E::B; // legal in C++11

enum class F { A, B, C };

A; // error
F::B;
</code></pre>

blocks|key|215654|text|这个代码是错误的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|215655|enum+Days+{Saturday,+Sunday,+Tuesday,+Wednesday,+Thursday,+Friday};
Days+day+=+Days.Saturday;
if+(day+==+Days.Saturday)|code-block|syntax|javascript|215656|因为Days既不是作用域，也不是对象。它是一种类型。并且类型本身没有成员。您所写的内容等同于std::string.clear。std::string是一个类型，所以你不能对它使用.。您可以在类的实例上使用.。|offset|length|style|CODE|215657|不幸的是，枚举是神奇的，所以类比到此为止。因为对于类，您可以执行std::string::clear来获取指向成员函数的指针，但在C%2B%2B03中，Days::Sunday是无效的。(这是可悲的)。这是因为C%2B%2B+(在某种程度上)与C向后兼容，而C没有名称空间，所以枚举必须在全局名称空间中。所以语法很简单：|215658|enum+Days+{Saturday,+Sunday,+Tuesday,+Wednesday,+Thursday,+Friday};
Days+day+=+Saturday;
if+(day+==+Saturday)|215659|幸运的是，Mike+Seymour注意到C%2B%2B11中已经解决了这个问题，将enum更改为enum+class，它就有了自己的作用域；因此Days::Sunday不仅有效，而且是访问Sunday的唯一方法。快乐的日子！|215660|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/204847/mike-seymour^0|0|0|2|4|1A|H|1S|B|2I|1|2V|1|0|W|I|20|C|0|0|11|4|18|A|1W|C|2I|6|5|C|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@$I|13|J|14|K|L]|$I|15|J|16|K|L]|$I|17|J|18|K|L]|$I|19|J|1A|K|L]|$I|1B|J|1C|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1D|8|@$I|1E|J|1F|K|L]|$I|1G|J|1H|K|L]]|9|@]|A|$]]|$1|O|3|P|5|D|7|1I|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|1J|8|@$I|1K|J|1L|K|L]|$I|1M|J|1N|K|L]|$I|1O|J|1P|K|L]|$I|1Q|J|1R|K|L]]|9|@$I|1S|J|1T|1|1U]]|A|$]]|$1|S|3|-4|5|6|7|1V|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

This code is wrong:

<pre><code>enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};
Days day = Days.Saturday;
if (day == Days.Saturday)
</code></pre>

Because <code>Days</code> is not a scope, nor object. It is a type. And Types themselves don't have members. What you wrote is the equivalent to <code>std::string.clear</code>. <code>std::string</code> is a type, so you can't use <code>.</code> on it. You use <code>.</code> on an instance of a class.

Unfortunately, enums are magical and so the analogy stops there. Because with a class, you can do <code>std::string::clear</code> to get a pointer to the member function, but in C++03, <code>Days::Sunday</code> is invalid. (Which is sad). This is because C++ is (somewhat) backwards compatable with C, and C had no namespaces, so enumerations had to be in the global namespace. So the syntax is simply:

<pre><code>enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};
Days day = Saturday;
if (day == Saturday)
</code></pre>

Fortunately, <a href="https://stackoverflow.com/users/204847/mike-seymour">Mike Seymour</a> observes that this has been addressed in C++11. Change <code>enum</code> to <code>enum class</code> and it gets its own scope; so <code>Days::Sunday</code> is not only valid, but is the only way to access <code>Sunday</code>. Happy days!

blocks|key|212890|text|您可以使用一个技巧来使用作用域，只需以如下方式声明枚举：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|212891|struct+Days+
{
+++enum+type
+++{
++++++Saturday,Sunday,Tuesday,Wednesday,Thursday,Friday
+++};
};

Days::type+day+=+Days::Saturday;
if+(day+==+Days::Saturday)|code-block|syntax|javascript|212892|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can use a trick to use scopes as you wish, just declare enum in such way:

<pre><code>struct Days 
{
 enum type
 {
 Saturday,Sunday,Tuesday,Wednesday,Thursday,Friday
 };
};

Days::type day = Days::Saturday;
if (day == Days::Saturday)
</code></pre>

blocks|key|3074206|text|我认为您的根本问题是使用.而不是::，后者将使用名称空间。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3074207|尝试：|3074208|enum+Days+{Saturday,+Sunday,+Tuesday,+Wednesday,+Thursday,+Friday};
Days+day+=+Days::Saturday;
if(Days::Saturday+==+day)++//+I+like+literals+before+variables+:)
{
++++std::cout<<"Ok+its+Saturday";
}|code-block|syntax|javascript|3074209|entityMap^0|C|1|G|2|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

I think your root issue is the use of <code>.</code> instead of <code>::</code>, which will use the namespace.

Try:

<pre><code>enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};
Days day = Days::Saturday;
if(Days::Saturday == day) // I like literals before variables :)
{
 std::cout&lt;&lt;"Ok its Saturday";
}
</code></pre>

blocks|key|2860802|text|虽然C%2B%2B+(不包括C%2B%2B11)具有枚举，但其中的值被“泄漏”到全局名称空间中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860803|如果您不想让它们泄漏(并且不需要使用枚举类型)，请考虑以下几点：|2860804|class+EnumName+{++
+++public:+++
++++++static+int+EnumVal1;++
++++++(more+definitions)++
};++
EnumName::EnumVal1+=+{value};++
if+([your+value]+==+EnumName::EnumVal1)++...|code-block|syntax|javascript|2860805|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

While C++ (excluding C++11) has enums, the values in them are "leaked" into the global namespace. 
If you don't want to have them leaked (and don't NEED to use the enum type), consider the following: 

<pre><code>class EnumName { 
 public: 
 static int EnumVal1; 
 (more definitions) 
}; 
EnumName::EnumVal1 = {value}; 
if ([your value] == EnumName::EnumVal1) ...
</code></pre>

blocks|key|3074290|text|您正在寻找强类型枚举，这是C%2B%2B11标准中提供的一个特性。它将枚举转换为具有作用域值的类。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3074291|使用您自己的代码示例，它是：|3074292|++enum+class+Days+{Saturday,+Sunday,+Tuesday,Wednesday,+Thursday,+Friday};
++Days+day+=+Days::Saturday;

++if+(day+==+Days::Saturday)++{
++++cout+<<+"+Today+is+Saturday+!"+<<+endl;
++}
++//int+day2+=+Days::Sunday;+//+Error!+invalid|code-block|syntax|javascript|3074293|使用::作为枚举的访问器将会失败，但是一些旧的编译器不支持它，一些IDE只是覆盖这个选项，并设置一个旧的C%2B%2B标准。|CODE|3074294|如果您使用的是GCC，请通过-std=c%2B%2B11或-std=gnu11启用C%2B11。|3074295|祝你快乐！|3074296|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/C%252B%252B11^0|5|5|D|5|0|0|0|0|2|2|0|E|A|P|A|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1C|8|@$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|R|3|S|5|6|7|1H|8|@]|D|@]|E|$]]|$1|T|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|U|$V|$5|W|X|Y|E|$Z|10]]]]

You are looking for strongly typed enumerations, a feature available in the <a href="https://en.wikipedia.org/wiki/C%2B%2B11" rel="noreferrer">C++11</a> standard. It turns enumerations into classes with scope values.

Using your own code example, it is:

<pre><code> enum class Days {Saturday, Sunday, Tuesday,Wednesday, Thursday, Friday};
 Days day = Days::Saturday;

 if (day == Days::Saturday) {
 cout &lt;&lt; " Today is Saturday !" &lt;&lt; endl;
 }
 //int day2 = Days::Sunday; // Error! invalid
</code></pre>

Using <code>::</code> as accessors to enumerations will fail if targeting a C++ standard prior C++11. But some old compilers doesn't supported it, as well some IDEs just override this option, and set a old C++ std.

If you are using GCC, enable C+11 with -std=c++11 or -std=gnu11 .

Be happy!

blocks|key|3074328|text|如果您仍在使用C%2B%2B03并希望使用枚举，则应该在名称空间中使用枚举。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3074329|namespace+Daysofweek{
enum+Days+{Saturday,+Sunday,+Tuesday,Wednesday,+Thursday,+Friday};
}|code-block|syntax|javascript|3074330|您可以在名称空间之外使用枚举，如|3074331|Daysofweek::Days+day+=+Daysofweek::Saturday;

if+(day+==+Daysofweek::Saturday)
{
++++std::cout<<"Ok+its+Saturday";
}|3074332|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you are still using C++03 and want to use enums, you should be using enums inside a namespace. 
Eg:

<pre><code>namespace Daysofweek{
enum Days {Saturday, Sunday, Tuesday,Wednesday, Thursday, Friday};
}
</code></pre>

You can use the enum outside the namespace like,

<pre><code>Daysofweek::Days day = Daysofweek::Saturday;

if (day == Daysofweek::Saturday)
{
 std::cout&lt;&lt;"Ok its Saturday";
}
</code></pre>

blocks|key|218013|text|如果我们想要严格的类型安全和作用域枚举，在C%2B%2B11中使用enum+class是很好的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|218014|如果我们必须在C%2B%2B98中工作，我们可以使用InitializeSahib，San给出的建议来启用作用域枚举。|218015|如果我们也想要严格的类型安全，下面的代码可以实现像enum这样的东西。|218016|#include+<iostream>
class+Color
{
public:
++++static+Color+RED()
++++{
++++++++return+Color(0);
++++}
++++static+Color+BLUE()
++++{
++++++++return+Color(1);
++++}
++++bool+operator==(const+Color+&rhs)+const
++++{
++++++++return+this->value+==+rhs.value;
++++}
++++bool+operator!=(const+Color+&rhs)+const
++++{
++++++++return+!(*this+==+rhs);
++++}

private:
++++explicit+Color(int+value_)+:+value(value_)+{}
++++int+value;
};

int+main()
{
++++Color+color+=+Color::RED();
++++if+(color+==+Color::RED())
++++{
++++++++std::cout+<<+"red"+<<+std::endl;
++++}
++++return+0;
}|code-block|syntax|javascript|218017|代码由book+Effective+C%2B%2B第3:+18项中的班级月份示例修改而来|218018|entityMap^0|T|A|0|M|F|12|3|0|P|4|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|13|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

If we want the strict type safety and scoped enum, using <code>enum class</code> is good in C++11.

If we had to work in C++98, we can using the advice given by <code>InitializeSahib</code>,<code>San</code> to enable the scoped enum.

If we also want the strict type safety, the follow code can implement somthing like <code>enum</code>.

<pre><code>#include &lt;iostream&gt;
class Color
{
public:
 static Color RED()
 {
 return Color(0);
 }
 static Color BLUE()
 {
 return Color(1);
 }
 bool operator==(const Color &amp;rhs) const
 {
 return this-&gt;value == rhs.value;
 }
 bool operator!=(const Color &amp;rhs) const
 {
 return !(*this == rhs);
 }

private:
 explicit Color(int value_) : value(value_) {}
 int value;
};

int main()
{
 Color color = Color::RED();
 if (color == Color::RED())
 {
 std::cout &lt;&lt; "red" &lt;&lt; std::endl;
 }
 return 0;
}
</code></pre>

The code is modified from the class Month example in book Effective C++ 3rd: Item 18

Suppose we have an <code>enum</code> like the following:

<pre><code>enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};
</code></pre>

I want to create an instance of this <code>enum</code> and initialize it with a proper value, so I do:

<pre><code>Days day = Days.Saturday;
</code></pre>

Now I want to check my variable or instance with an existing <code>enum</code> value, so I do:

<pre><code>if (day == Days.Saturday)
{
 std::cout &lt;&lt; "Ok its Saturday";
}
</code></pre>

Which gives me a compilation error:

<blockquote>
 error: expected primary-expression before ‘.’ token
</blockquote>

So to be clear, what is the difference between saying:

<pre><code>if (day == Days.Saturday) // Causes compilation error
</code></pre>

and

<pre><code>if (day == Saturday)
</code></pre>

?

What do these two actually refer to, in that one is OK and one causes a compilation error?

How to use enums in C++

编译器

假设我们有一个如下所示的enum：enum Days {Saturday, Sunday, Tuesday, Wednesday, Thursday, Friday};我想创建此enum的一个实例，并使用适当的值对其进行初始化，因此我这样做了：Days day = Days.Saturday;现在我想用现有的enum值...

问如何在C++中使用枚举
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