在函数中未定义的引用 c++

我总是收到一个奇怪的错误。

usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o：

在函数_start中：>(.text+0x20(：对主的未定义引用/tmp/cc4ZqKzy.o：

在函数 'Sep：：Building：：Building(Sep：：Field：：FieldType，>std：：__cxx11：：basic_string，>std：：分配器>， char， bool， bool， unsigned int， unsigned int(：

Building.cpp：(.text+0x3c(：未定义对Sep：：Field：：Field((的引用 收集2：

错误：LD 返回 1 个退出状态

我读了很多关于这个问题的文章，但没有一个是相同的。我包含了所有的标题，还添加了ifndef守卫。

主.cpp：

#include "Field.h"
#include "Building.h"
namespace Sep
{
just some returns...
}
int main(int argc, char *argv[])
{
Sep::Building Haus(Sep::Field::FieldType::HOME,"HOME", 'H', true, true, 100, 100);
std::cout << "HAUS ABREV:" << Haus.getAbbrevationOnField() << 'n';
}

字段.h

#include <cstring>
#include <string>
#include <iostream>
#include <memory>

#ifndef FIELD_H
#define FIELD_H
namespace Sep
{
//----------------------------------------------------------------------------
// Field class, containing all needed information to create a Field object
//
class Field
{
public :
enum FieldType 
{GRASS, WATER, OBSTACLE, STREET, HOME, MARKET, CLINIC, TOWNHALL};
private:
FieldType type_;
std::string name_;
char abbrevation_;
bool buildable_;
bool destroyable_;
unsigned int build_cost_;
unsigned int destroy_cost_;
public:
//------------------------------------------------------------------------
// Field constructors & destructor
//
Field();
Field(FieldType type);
~Field() noexcept;
//------------------------------------------------------------------------
//getters
//
Field::FieldType getFieldType() const { return type_; };
const char getAbbrevationOnField() const { return abbrevation_; };
//------------------------------------------------------------------------
//setters
//
static std::string getName(FieldType type);
FieldType getType() const;//steht oben in getFiel3dType Z55
void setType(FieldType type){type_ = type;};
void setName(std::string name){name_ = name;};
void setAbbrevation(char abbrev){abbrevation_ = abbrev;};
void setBuildable(bool buildable){buildable_ = buildable;};
void setDestroyable(bool destroyable){destroyable_ = destroyable;};
void setBuildCost(int b_cost){build_cost_ = b_cost;};
void setDestroyCost(int d_cost){destroy_cost_ = d_cost;};
};
}
#endif //FIELD.H

字段.cpp

#include "Field.h"
#include <cstring>
#include <string>
#include <iostream>
#include <memory>
using Sep::Field;

//------------------------------------------------------------------------------
// Setter of the private FieldType type_ to the given param
//
// @param the type of field to get set
//
Field::Field(FieldType type)
{
type_ = type;
};
Field::~Field(){};
//------------------------------------------------------------------------------
// Checks the type of a given field, returns the name of type as string
//
// @param type, the type of the field to check
//
// @return string the name of the type of the checked field
//
std::string Field::getName(FieldType type)
{
switch (type)
{
case GRASS:
return std::string("Grass");
case WATER:
return std::string("Water");
case OBSTACLE:
return std::string("Obstacle");
case STREET:
return std::string("Street");
case HOME:
return std::string("Home");
case MARKET:
return std::string("Market");
case CLINIC:
return std::string("Clinic");
case TOWNHALL:
return std::string("Town Hall");
default:
return std::string("Unknown Field");
}
};
//------------------------------------------------------------------------------
// getters
//
// Getter from the private FieldType type_
//
// @param none
//
// @return the type of type_ as FieldType
//
Field::FieldType Field::getType() const
{
return type_;
};

建筑.h

#ifndef BUILDING_H
#define BUILDING_H
#include "Field.h"
namespace Sep
{
class Building : public Field
{
private:
public:
Building(FieldType type, const std::string name, const char abbrevation, 
const bool buildable, const bool destroyable,
const unsigned int b_cost, const unsigned int d_cost);
~Building();
};
}
#endif //BUILDING_H

建筑.cpp

#include "Building.h"
#include "Field.h"
Sep::Building::Building(FieldType type, const std::string name, 
const char abbrevation, 
const bool buildable, const bool destroyable,
const unsigned int b_cost, const unsigned int d_cost)
{
Sep::Field::setType(type);
Sep::Field::setName(name);
Sep::Field::setAbbrevation(abbrevation);
Sep::Field::setBuildable(buildable);
Sep::Field::setDestroyable(destroyable);
Sep::Field::setBuildCost(b_cost);
Sep::Field::setDestroyCost(d_cost);
};
Sep::Building::~Building(){};

有人知道吗？因为我经常在这个项目中收到此错误，但在其他类中。 奇怪的是，程序似乎编译正确，但在开始时我得到这个 collect2：错误：ld 返回了 1 个退出状态。

感谢