结构没有在 C++ 中命名类型
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structure does not name a type in c++
提问by Kathick
I get an issue while return type is structure
返回类型是结构时出现问题
Example.h
class Example {
private:
typedef struct connection_header {
string url;
string method;
};
static connection_header get_connection_header();
};
Example.cpp
connection_header Example::get_connection_header() {
return NULL;
}
I am getting 'connection_header' does not name a type
我正进入（状态 'connection_header' does not name a type
may i know why is this error
我可以知道为什么会出现这个错误吗
回答by juanchopanza
You are using typedefwithout giving a name to the type. Just drop the typedef, it is not needed here:
您正在使用typedef而不给类型命名。只需删除typedef，这里不需要它：
struct connection_header {
string url;
string method;
};
Next, connection_headeris declared inside of the Exampleclass, so you need to fully qualify its name in the implementation when it is a return type:
接下来，connection_header在Example类内部声明，因此当它是返回类型时，您需要在实现中完全限定其名称：
Example::connection_header Example::get_connection_header()
回答by masoud
Try below code in cppfile, add Example::before connection_header:
在cpp文件中尝试以下代码，在Example::之前添加connection_header：
Example::connection_header Example::get_connection_header() {
return NULL;
}
connection_headeris defined inside Exampleso you should give it its definition scope.
connection_header是在里面定义的，Example所以你应该给它定义范围。
Also, the keyword typedefwill be ignored in C++. You can omit it
此外，该关键字typedef在 C++ 中将被忽略。你可以省略它
回答by Basile Starynkevitch
First, in C++ (but not C) every structor classnames a type. So if you declare a struct connection_header, you also get a connection_headertype, so you can later declare connection_header varsome variable.
首先，在 C++（但不是 C）中，每个struct或class命名一个类型。所以如果你声明 a struct connection_header，你也会得到一个connection_header类型，所以你以后可以声明connection_header var一些变量。
Then, typedefboth in C and C++ needs a type and a name. For example:
然后，typedef在 C 和 C++ 中都需要一个类型和一个名称。例如：
typedef long my_number_type;
declares my_number_typeas a synonym for long
声明my_number_type为同义词long
So as others pointed out, drop the typedef
所以正如其他人指出的那样，放弃 typedef
回答by Adam Erickson
In addition to the answers of others, I recommend that you do not nest the definition of your data structures. Create a separate external structfor connection_headerabove the Exampleclass.
除了其他人的答案，我建议您不要嵌套数据结构的定义。创建一个单独的外部struct对connection_header上述Exampleclass。
Example.h
struct ConnectionHeader {
string url;
string method;
};
class Example {
private:
ConnectionHeader connection_header;
static ConnectionHeader get_connection_header();
};
This is much simpler to debug, offers better reusability, and makes it easier to predict the results of auto. Otherwise, just make urland methodmembers of Exampleand have get_connection_header()update these values in-place, returning void.
这更容易调试，提供更好的可重用性，并且更容易预测auto. 否则，只需 makeurl和methodmembers ofExample并get_connection_header()就地更新这些值，返回void.
