Class HttpViewData

Synopsis

#include <lib/inc/drogon/HttpViewData.h>

class DROGON_EXPORT HttpViewData

Description

This class represents the data set displayed in views.

Mentioned in

• View / The use of views
• View / A simple example
• Session / Session object

Methods

	get	The function template is used to get an item in the data set by the key parameter.
	htmlTranslate overload	Translate some special characters to HTML format.
	insert overload	Insert an item identified by the key parameter into the data set;.
	insertAsString	Insert an item identified by the key parameter into the data set; The item is converted to a string.
	insertFormattedString	Insert a formated string identified by the key parameter.
	needTranslation
	operator[]	Get the 'any' object by the key parameter.

Source

Lines 32-171 in lib/inc/drogon/HttpViewData.h.

class DROGON_EXPORT HttpViewData
{
  public:
    /// The function template is used to get an item in the data set by the key
    /// parameter.
    template <typename T>
    const T &get(const std::string &key) const
    {
        const static T nullVal = T();
        auto it = viewData_.find(key);
        if (it != viewData_.end())
        {
            if (typeid(T) == it->second.type())
            {
                return *(any_cast<T>(&(it->second)));
            }
            else
            {
                LOG_ERROR << "Bad type";
            }
        }
        return nullVal;
    }

    /// Insert an item identified by the key parameter into the data set;
    void insert(const std::string &key, any &&obj)
    {
        viewData_[key] = std::move(obj);
    }
    void insert(const std::string &key, const any &obj)
    {
        viewData_[key] = obj;
    }

    /// Insert an item identified by the key parameter into the data set; The
    /// item is converted to a string.
    template <typename T>
    void insertAsString(const std::string &key, T &&val)
    {
        std::stringstream ss;
        ss << val;
        viewData_[key] = ss.str();
    }

    /// Insert a formated string identified by the key parameter.
    void insertFormattedString(const std::string &key, const char *format, ...)
    {
        std::string strBuffer;
        strBuffer.resize(128);
        va_list ap, backup_ap;
        va_start(ap, format);
        va_copy(backup_ap, ap);
        auto result = vsnprintf((char *)strBuffer.data(),
                                strBuffer.size(),
                                format,
                                backup_ap);
        va_end(backup_ap);
        if ((result >= 0) &&
            ((std::string::size_type)result < strBuffer.size()))
        {
            strBuffer.resize(result);
        }
        else
        {
            while (true)
            {
                if (result < 0)
                {
                    // Older snprintf() behavior. Just try doubling the buffer
                    // size
                    strBuffer.resize(strBuffer.size() * 2);
                }
                else
                {
                    strBuffer.resize(result + 1);
                }

                va_copy(backup_ap, ap);
                auto result = vsnprintf((char *)strBuffer.data(),
                                        strBuffer.size(),
                                        format,
                                        backup_ap);
                va_end(backup_ap);

                if ((result >= 0) &&
                    ((std::string::size_type)result < strBuffer.size()))
                {
                    strBuffer.resize(result);
                    break;
                }
            }
        }
        va_end(ap);
        viewData_[key] = std::move(strBuffer);
    }

    /// Get the 'any' object by the key parameter.
    any &operator[](const std::string &key) const
    {
        return viewData_[key];
    }

    /// Translate some special characters to HTML format
    /**
     * such as:
     * @code
       " --> &quot;
       & --> &amp;
       < --> &lt;
       > --> &gt;
       @endcode
     */
    static std::string htmlTranslate(const char *str, size_t length);
    static std::string htmlTranslate(const string_view &str)
    {
        return htmlTranslate(str.data(), str.length());
    }

    static bool needTranslation(const string_view &str)
    {
        for (auto const &c : str)
        {
            switch (c)
            {
                case '"':
                case '&':
                case '<':
                case '>':
                    return true;
                default:
                    continue;
            }
        }
        return false;
    }

  protected:
    using ViewDataMap = std::unordered_map<std::string, any>;
    mutable ViewDataMap viewData_;
};

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