Question

我实现了一个AVL树作为库的一部分，并且无法弄清楚它是CppUnit，NetBeans 8，我的C ++技能（模板）还是其他什么问题，但是代码编译为静态库但是当与CppUnit或独立应用程序一起使用时，我得到undefined reference to MyProject::Utilities::AVLTree<int, char>::function。

我在保持相同错误的同时尽可能地减少了代码。

AVLTree.h

namespace MyProject {
    namespace Utilities {
        template <typename KeyType, typename ValueType> class AVLTree {
        public:
            AVLTree();
            AVLTree(const MyProject::Utilities::AVLTree<KeyType, ValueType>& orig);
            virtual ~AVLTree();
            bool hasRoot() const;
            MyProject::Utilities::AVLNode<KeyType, ValueType>* getRoot() const;

        protected:
            void setRoot(MyProject::Utilities::AVLNode<KeyType, ValueType>* _node);

        private:
            MyProject::Utilities::AVLNode<KeyType, ValueType>* _root;
            unsigned int _size;

        };
    };
};

AVLTree.cpp

template <typename KeyType, typename ValueType> MyProject::Utilities::AVLTree<KeyType, ValueType>::AVLTree() {
    this->setRoot(NULL);
    this->_size = 0;
}

template <typename KeyType, typename ValueType> MyProject::Utilities::AVLTree<KeyType, ValueType>::AVLTree(const MyProject::Utilities::AVLTree<KeyType, ValueType>& orig) {
    this->setRoot(orig.getRoot());
    this->_size = orig.size();
}

template <typename KeyType, typename ValueType> MyProject::Utilities::AVLTree<KeyType, ValueType>::~AVLTree() {
    // this->clear();
}

template <typename KeyType, typename ValueType> void MyProject::Utilities::AVLTree<KeyType, ValueType>::setRoot(MyProject::Utilities::AVLNode<KeyType, ValueType>* _root) {
    this->_root = _root;
}

template <typename KeyType, typename ValueType> bool MyProject::Utilities::AVLTree<KeyType, ValueType>::hasRoot() const {
    return this->getRoot() != NULL;
}

template <typename KeyType, typename ValueType> MyProject::Utilities::AVLNode<KeyType, ValueType>* MyProject::Utilities::AVLTree<KeyType, ValueType>::getRoot() const {
    return this->_root;
}

的main.cpp

#include <cstdlib>
#include "AVLTree.h"

int main(int argc, char** argv) {
    MyProject::Utilities::AVLTree<int, char> instance;
    for (unsigned int i = 0; i < 20; ++i) {
        instance.hasRoot();
        // instance.insert(i, (char) (65 + i));
    }

    //instance.graphviz("./test.dot");
    return 0;
}

Netbeans 8在尝试构建cppapplication_1

时返回以下错误

g++    -c -g -I../../Documents/MyProject/src/header -MMD -MP -MF "build/Debug/GNU-Linux-x86/main.o.d" -o build/Debug/GNU-Linux-x86/main.o main.cpp
mkdir -p dist/Debug/GNU-Linux-x86
g++     -o dist/Debug/GNU-Linux-x86/cppapplication_1 build/Debug/GNU-Linux-x86/main.o -L../../Documents/MyProject/dist/Debug/GNU-Linux-x86 -lmyproject
build/Debug/GNU-Linux-x86/main.o: In function `main':
/home/.../CppApplication_1/main.cpp:6: undefined reference to `MyProject::Utilities::AVLTree<int, char>::AVLTree()'
/home/.../CppApplication_1/main.cpp:8: undefined reference to `MyProject::Utilities::AVLTree<int, char>::hasRoot() const'
/home/.../CppApplication_1/main.cpp:12: undefined reference to `MyProject::Utilities::AVLTree<int, char>::~AVLTree()'
/home/.../CppApplication_1/main.cpp:12: undefined reference to `MyProject::Utilities::AVLTree<int, char>::~AVLTree()'
collect2: error: ld returned 1 exit status

以下代码会产生大约100个不同内容的错误......我不是故意愚蠢但是对于我的生活，我无法弄清楚出了什么问题，也找不到工作使用的示例或教程...

src/header/AVLTree.h:16:23: error: declaration of ‘class KeyType’
         template <typename KeyType, typename ValueType> AVLTree();
src/header/AVLTree.h:14:19: error:  shadows template parm ‘class KeyType’
     template <typename KeyType, typename ValueType> class AVLTree {
src/header/AVLTree.h:16:41: error: declaration of ‘class ValueType’
         template <typename KeyType, typename ValueType> AVLTree();
src/header/AVLTree.h:14:37: error:  shadows template parm ‘class ValueType’
     template <typename KeyType, typename ValueType> class AVLTree {
In file included from src/AVLTree.cpp:1:0:
src/header/AVLTree.h:18:23: error: declaration of ‘class KeyType’
         template <typename KeyType, typename ValueType> virtual ~AVLTree();

AVLTree.h

namespace MyProject {

    namespace Utilities {

        template <typename KeyType, typename ValueType> class AVLTree {
        public:
            template <typename KeyType, typename ValueType> AVLTree();
            template <typename KeyType, typename ValueType> AVLTree(const MyProject::Utilities::AVLTree<KeyType, ValueType>& orig);
            template <typename KeyType, typename ValueType> virtual ~AVLTree();
            template <typename KeyType, typename ValueType> bool hasRoot() const;
            template <typename KeyType, typename ValueType> MyProject::Utilities::AVLNode<KeyType, ValueType>* getRoot() const;

        protected:
            void setRoot(MyProject::Utilities::AVLNode<KeyType, ValueType>* _node);

        private:
            MyProject::Utilities::AVLNode<KeyType, ValueType>* _root;

        };
    };
};

AVLTree.cpp（指定了类型）

MyProject::Utilities::AVLTree<KeyType, ValueType>::AVLTree() {
    this->setRoot(NULL);
}

MyProject::Utilities::AVLTree<KeyType, ValueType>::AVLTree(const MyProject::Utilities::AVLTree<KeyType, ValueType>& orig) {
    this->setRoot(orig.getRoot());
    // this->_size = orig.size();
}

MyProject::Utilities::AVLTree<KeyType, ValueType>::~AVLTree() {
    // this->clear();
}

void MyProject::Utilities::AVLTree<KeyType, ValueType>::setRoot(MyProject::Utilities::AVLNode<KeyType, ValueType>* _root) {
    this->_root = _root;
}

bool MyProject::Utilities::AVLTree<KeyType, ValueType>::hasRoot() const {
    return this->getRoot() != NULL;
}

MyProject::Utilities::AVLNode<KeyType, ValueType>* MyProject::Utilities::AVLTree<KeyType, ValueType>::getRoot() const {
    return this->_root;
}

AVLTree.cpp（未指定类型）

MyProject::Utilities::AVLTree::AVLTree() {
    this->setRoot(NULL);
}

MyProject::Utilities::AVLTree::AVLTree(const MyProject::Utilities::AVLTree& orig) {
    this->setRoot(orig.getRoot());
    // this->_size = orig.size();
}

MyProject::Utilities::AVLTree::~AVLTree() {
    // this->clear();
}

void MyProject::Utilities::AVLTree::setRoot(MyProject::Utilities::AVLNode<KeyType, ValueType>* _root) {
    this->_root = _root;
}

bool MyProject::Utilities::AVLTree::hasRoot() const {
    return this->getRoot() != NULL;
}

MyProject::Utilities::AVLNode<KeyType, ValueType>* MyProject::Utilities::AVLTree::getRoot() const {
    return this->_root;
}

Answer 1

模板不是功能。它们不存在于代码中。它们只是一些蓝图，或者说明了在知道所有模板参数后如何实际生成函数的说明。因此，所有模板都必须驻留在头文件中，以便在知道所有模板参数后可见。 ~~将所有模板代码从AVLTree.cpp移动到AVLTree.h~~ 。仅仅移动还不够，还必须改变它。

以下是在我的Visual Studio上编译的示例：

namespace My {
    namespace Util {
        template <typename KeyType, typename ValueType> class World {
        public:
            World()
            {
            }

            World(const My::Util::World<KeyType, ValueType>& orig)
            {
            }

            virtual ~World()
            {
            }

            bool Hello() const
            {
                return true;
            }
        };
    };
};

使用如下代码：

My::Util::World<int, char> world;
world.Hello();

可以将所有函数与类声明分开，但它没有任何实际意义，因为所有分离的代码无论如何都必须是可见的。它看起来像这样：

namespace My {
    namespace Util {
        template <typename KeyType, typename ValueType> class World {
            ....
            bool Hello() const;
        };
    };
};

template<typename KeyType, typename ValueType>
bool My::Util::World<KeyType, ValueType>::Hello() const
{
    return true;
}

我试过你的例子，它对我有用。我刚刚在类模板之后放置了所有函数模板，并注释掉了所有处理AVLNode的代码，并进行了编译。所以我的原始陈述似乎是有效的：只需将所有模板代码从源移动到标头。您的第二个示例代码与您的第一个代码不同。你应该做的只是搬家。

在C ++中链接静态库时未定义的引用....

1 个答案: