模板和嵌套类/结构
我有一个简单的容器：
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
//...
};
现在，有一个名为 _search 的函数，它搜索列表并返回对匹配节点的引用。现在，当我提到函数的返回类型时，我认为它应该是 list。这是对的吗？当我内联定义函数时，它工作得很好：
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
node* _search {
node* temp;
// search for the node
return temp;
}
};
但是，如果我在类外部定义函数，
template <class nodeType> list<nodeType>::node* list<nodeType>::_search() {
//function
}
它就不起作用。编译器给出一个错误，指出 Expected constructor before list 或其他内容。该错误与此类似。我目前没有可以测试它的机器。
真诚感谢任何帮助。
I have a simple container :
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
//...
};
Now, there is a function called _search which searches the list and returns a reference to the node which matched. Now, when I am referring to the return-type of the function, I think it should be list<nodeType>::node*. Is this right? When I define the function inline, it works perfectly:
template <class nodeType> list {
public:
struct node {
nodeType info;
node* next;
};
node* _search {
node* temp;
// search for the node
return temp;
}
};
But, if I define the function outside the class,
template <class nodeType> list<nodeType>::node* list<nodeType>::_search() {
//function
}
it doesn't work. The compiler gives an error saying Expected constructor before list<nodeType>::_search or something. The error is something similar to this. I don't have a machine on which I can test it currently.
Any help is sincerely appreciated.
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这是因为
node是一个依赖类型。您需要按如下方式编写签名（请注意，为了清楚起见，我将其分成两行）请注意
typename关键字的使用。that's because
nodeis a dependent type. You need to write the signature as follows (note that I have broken it into 2 lines for clarity)Note the use of the
typenamekeyword.您需要使用关键字
typename告诉编译器node是一个类型。否则它会认为 Node 是中的。每当您在列表实现中使用节点作为类型时，请添加static变量类列表typename。You need to tell the compiler that
nodeis a type using the keywordtypename.Otherwise it will think node as astaticvariable inclass list. Addtypenamewhenever you use node as a type in your implementation of list.