CODEWITHSUNDEEP
c++templatesgenerics
user1423893
user1423893

Reputation: 796

Function template - Returning T based on input class? - C++

I have created a function template for loading my settings from a binary file.

template<class T> T LoadSettings(const std::string &fileName)
{
    // Load settings
    T settings;

    std::string filePath(LOCAL_FILE_DIR);
    filePath.append(fileName);

    std::ifstream file(filePath, std::ios::in | std::ios::binary);

    if (file.is_open())
    {
        if (!settings.ParseFromIstream(&file)) 
        {
            throw ExceptionMessage("Failed to parse TextureAtlasSettings");
        }
    }
    else
    {
        throw ExceptionMessage("Failed to open file");
    }

    return settings;
};

I would like to be able to invoke the function and return the appropriate settings class.

Coming from C# I would do the following.

MySettingsClass settings = LoadSettings<MySettingsClass>("FileName.bin");

How can I do the same thing in C++?

EDIT:

I should be more generic!

throw std::runtime_error("Failed to parse " + typeid(T).name());

Upvotes: 0

Views: 142

Answers (2)

111111
111111

Reputation: 16148

 template<typename T> 
 T LoadSettings(const std::string& fileName)
 {
    // Load settings
    T settings;

    std::string filePath(LOCAL_FILE_DIR);
    filePath += fileName; 

     std::ifstream file(filePath, std::ios::in | std::ios::binary); 

     if (file && settings.ParseFromIstream(file)) 
     {    
           return settings;
     }
     throw std::runtime_error("Failed to parse TextureAtlasSettings");
 }

This should work, however you might want to consider writing an extraction operator foe your types T.

Upvotes: 0

Denis Ermolin
Denis Ermolin

Reputation: 5546

Then use this syntax in C++

MySettingsClass settings = LoadSettings<MySettingsClass>(std::string("FileName.bin"));

Upvotes: 1

Related Questions