Question

希望我错过了一些非常明显的东西：

尝试使用某些向量作为容器，使用资产属性修饰符（类）设置资产（类）的值。这似乎在函数调用期间有效，但是当使用get调用来跟随set调用进行确认时，就好像没有发生set调用一样。请参阅下面的代码和输出：

asset.h文件：

//selectedOffice: '',
selectedProductType: [],
officeList: [
    {
        code: 'Blue Office',
        jira: true
    },
    {
        code: 'Red Office',
        jira: false
    }
...snip...
],

productList: [
    {
        type: 'comics',
        url: 'www.comicsurl.com'
    },
    {
        type: 'videos',
        url: 'www.videosurl.com'
    }

....snip...
]

AddProperty正常工作，所以我省略了它，并且.cpp不相关。只是将push_back插入向量中以添加值，以及一些索引跟踪。

在资产属性标题中：

namespace assets {
class Asset 
{
  friend class AssetPropertyModifier;
  std::vector<properties::AssetPropertyDouble> asset_property_double_;
  enum property_id_ { ZERO, USHORT, FLOAT, INT, UINT, DOUBLE, VEC3, STRING, 
       BOOL};
public:
  void AddProperty(std::string property_name, double property_value);
};//class Asset
}//namespace assets

这是APM标题：

namepsace properties {
struct AssetPropertyDouble
{
private:
  friend class AssetPropertyModifier;
  double real_number_value_;
public:
  AssetPropertyDouble(double d) : real_number_value_(d) {}
};//struct AssetPropertyDouble
}//namespace proeprties

在APM .cpp文件中：

namespace assets {
class Asset;
class AssetPropertyModifier
{
  int LookUpVectorIndex(Asset a, int type , int index);
  int LookUpNameIndex(Asset a, std::string s);
public:
  double GetPropertyValue(Asset a, std::string property_name, 
         double not_used_just_an_overloader);
  void SetPropertyValue(Asset a, std::string property_name, 
       double new_double_value);
};//class AssetPropertyModifier
}//namespace assets

然后，当我使用这个原型时，我会发生以下事情：

来自main.cpp示例：

namespace assets {

//LookUpNameIndex definition
//LookUpVectorIndex defintion

double AssetPropertyModifier::GetPropertyValue(Asset a, 
                              std::string property_name, 
                              double not_used_just_an_overloader)
{
  //Using Verbose output to debug:
  std::cout << "------------GET-------------------" << std::endl;
  int name_index = LookUpNameIndex(a, property_name);
  std::cout << "names vector index is " << name_index << std::endl;
  int double_index = LookUpVectorIndex(a, a.DOUBLE, name_index);
  std::cout << "double property vector index is " << double_index << 
       std::endl;
  double property_value = 
       a.asset_property_double_.at(double_index).real_number_value_;
  std::cout << property_name << " are equal to " << property_value << 
       std::endl;
  return property_value;
}

void AssetPropertyModifier::SetPropertyValue(Asset a, 
                            std::string property_name, 
                            double new_double_value)
{
   //Using Verbose output to debug:
  std::cout << "------------SET-------------------" << std::endl;
  int name_index = LookUpNameIndex(a, property_name);
  std::cout << "names vector index is " << name_index << std::endl;
  int double_index = LookUpVectorIndex(a, a.DOUBLE, name_index);
  std::cout << "double vector index is " << double_index << std::endl;
  a.asset_property_double_.at(double_index).real_number_value_ = 
       new_double_value;
  std::cout << property_name << " was changed to " <<
        a.asset_property_double_.at(double_index).real_number_value_
        << std::endl;
}//SetPropertyValue

}//namespace assets

这是结果输出：

std::string some_name = "Property Name";
double some_initial_value = 5.5;
double some_new_value = 4.4;
assets::AssetPropertyModifier apm;
assets::Asset my_asset;

main {
  my_asset.AddProperty(some_name, some_initial_value);
  std::cout << "Current value = " << apm.GetPropertyValue(my_asset, 
       some_name , _DOUBLE_)
       << std::endl;

  apm.SetPropertyValue(my_asset, some_name , some_new_value );

  std::cout << "Current value = " << apm.GetPropertyValue(my_asset, 
       some_name , _DOUBLE_)
       << std::endl;
}

正如你在上面看到的那样，GET返回5.5并且SET声明它更新为4.4但是后面的GET仍然显示5.5。

我可以提供的另一件事来帮助解决这个问题，如果我将该属性设置为公共，以便我可以直接从main访问Asset属性以进行测试，它会正确更新：

------------GET-------------------
names vector index is 0
double property vector index is 0
Property Name are equal to 5.5
Current value = 5.5
------------SET-------------------
names vector index is 0
double vector index is 0
Property Name was changed to 4.4
------------GET-------------------
names vector index is 0
double property vector index is 0
Property Name are equal to 5.5
Current value = 5.5

该输出是：

//hard SET with public access to the vector and the property struct value
my_asset.asset_property_double_.at(0).real_number_value_ = 3.3;
//hard GET with public access:
std::cout << my_asset.asset_property_double_.at(0).real_number_value_ << 
     std::endl;
//GET through APM but with public values still enabled:
std::cout << "Current value = " << apm.GetPropertyValue(my_asset, some_name, 
     _DOUBLE_)
    << std::endl;

有谁知道为什么SET功能没有坚持上面？在此先感谢您的帮助！

Answer 1

您传递的是资产的副本，而不是对资产的引用，因此您实际上只是更新副本，而不是实际的副本。您需要通过引用传递：

void AssetPropertyModifier::SetPropertyValue(Asset& a,        //<----added '&'
                            std::string property_name, 
                            double new_double_value)
{
   //Using Verbose output to debug:
  std::cout << "------------SET-------------------" << std::endl;
  int name_index = LookUpNameIndex(a, property_name);
  std::cout << "names vector index is " << name_index << std::endl;
  int double_index = LookUpVectorIndex(a, a.DOUBLE, name_index);
  std::cout << "double vector index is " << double_index << std::endl;
  a.asset_property_double_.at(double_index).real_number_value_ = 
       new_double_value;
  std::cout << property_name << " was changed to " <<
        a.asset_property_double_.at(double_index).real_number_value_
        << std::endl;
}//SetPropertyValue

C ++ ::设置值函数设置函数内部，但后跟Get函数设置值消失

1 个答案: