如何在一个类中注入依赖项，这个类依赖于一个类，而这个类依赖于C++；？ 我试图在C++项目中实现依赖注入。然而，由于依赖项的结构，我得到了一个无法解决的分段错误

作为示例，我构建了以下类和接口。我有一个名为MyClass的类，它依赖于依赖关系。依赖项依赖于其他依赖项。为了进行适当的测试，我从接口继承了依赖项，即IDependency和IOtherDependency。OtherDependency有一个函数some_function（）

在main.cpp中，我创建了MyClass的一个实例，然后尝试调用一些函数（）。不幸的是，这会产生分段错误：

Segmentation fault (core dumped)

MyClass.h：

#ifndef MYCLASS_H
#define MYCLASS_H

#include "IDependency.h"

class MyClass
{
public:
    MyClass(IDependency *dependency);
    ~MyClass();

    IDependency *_dependency = nullptr;
};

#endif

MyClass.cpp：

#include "MyClass.h"

#include <iostream>

MyClass::MyClass(IDependency *dependency) : _dependency(dependency) {}

MyClass::~MyClass() {}

Dependency.cpp：

#include "Dependency.h"

#include <iostream>

Dependency::Dependency(IOtherDependency *other_dependency) : _other_dependency(other_dependency) {}

Dependency::~Dependency() {}

#include "OtherDependency.h"

#include <iostream>

OtherDependency::OtherDependency() {}

OtherDependency::~OtherDependency() {}

void OtherDependency::some_function()
{
    std::cout << "I am OtherDependency." << std::endl;
}

OtherDependency.h：

#ifndef DEPENDENCY_H
#define DEPENDENCY_H

#include "IDependency.h"
#include "IOtherDependency.h"

class Dependency : public IDependency
{
public:
    Dependency(IOtherDependency *other_dependency);
    ~Dependency();

    IOtherDependency *_other_dependency = nullptr;
};

#endif

#ifndef IDEPENDENCY_H
#define IDEPENDENCY_H

#include "IOtherDependency.h"

class IDependency
{
public:
    IOtherDependency *_other_dependency;
};

#endif

#ifndef OTHERDEPENDENCY_H
#define OTHERDEPENDENCY_H

#include "IOtherDependency.h"

class OtherDependency : public IOtherDependency
{
public:
    OtherDependency();
    ~OtherDependency();

    void some_function();
};

#endif

#ifndef IOTHERDEPENDENCY_H
#define IOTHERDEPENDENCY_H

class IOtherDependency
{
public:
    virtual void some_function() = 0;
};

#endif

OtherDependency.cpp：

#include "Dependency.h"

#include <iostream>

Dependency::Dependency(IOtherDependency *other_dependency) : _other_dependency(other_dependency) {}

Dependency::~Dependency() {}

#include "OtherDependency.h"

#include <iostream>

OtherDependency::OtherDependency() {}

OtherDependency::~OtherDependency() {}

void OtherDependency::some_function()
{
    std::cout << "I am OtherDependency." << std::endl;
}

main.cpp：

int main()
{
    OtherDependency *other_dependency = new OtherDependency;
    Dependency *dependency = new Dependency(other_dependency);
    MyClass my_class(dependency);

    my_class._dependency->_other_dependency->some_function();
}

---

我做错了什么/我需要更改吗？

您有两个变量称为

\u other\u dependency

：一个在

IDependency

中，另一个在

dependency

中。

Dependency

构造函数初始化了后者，而

IDependency

类中的构造函数保留其默认的nullptr值

当您访问

my_class.\u dependency->\u other_dependency

时，

other_dependency

将是

IDependency

中的一个，因为

\u dependency

指向基类

解决此问题的一种方法是从

依赖项

中删除

其他依赖项

，并将值从

依赖项

构造函数传递到

IDependency

，以正确初始化其成员