Re: ideas for data binding?
Frank Buss wrote:
My goal is to simplify the amount of code for the GUI application code and
the serializers. An idea would be to use some kind of special data object
class instead of plain "string" and "int", but this is for an embedded
system and I don't know if this would slow down the program too much, so
maybe I need both: plain members and a list of data objects for each
object, which references the members, maybe with some kind of template
magic and function pointers for the getters and setters.
I think extra objects for all data members is the way to go. A solution
would be something like this:
class Attribute {
public:
Attribute(string attributeName);
virtual void loadValue(XmlNode* node) = 0;
virtual void saveValue(XmlNode* node) = 0;
virtual string getDisplayValue() = 0;
};
class IntAttribute : public Attribute {
public:
IntAttribute(string attributeName, int value);
int getValue();
void setValue(int value);
....
};
class StringAttribute : public Attribute ...
class EnumAttribute : public Attribute ...
Then I would derive all my data classes from one class:
class Data {
public:
virtual void loadValues(XmlNode* node);
virtual void saveValues(XmlNode* node);
private:
vector<Attribute*> m_attributes;
};
The loadValues and saveValues methods can be generic, except for saving
more complex objects than Attributes, or maybe with some kind of Container
Attribute class? But I want to avoid multiple inheritance.
The constructor of the book class could create the attribute-objects, but
maybe for faster access and compile time check, I'll need a member for each
attribute:
Book::Book() {
m_countAttribute = new intAttribute("Count", 0);
m_attributes.push_back(m_countAttribute);
}
The destructor of Data can delete all attributes.
Then I can use it in the GUI like this, without the need for a Handler
class for each member:
addNumberField(aBook->getCountAttribute());
There are still some open questions:
- do you think it is fast enough to use the attributes instead of plain
fields? E.g. I could rewrite the getCount in book as getCount() { return
m_countAttribute->getValue(); } (and the same for setCount)
- how can I reduce the amount of code for defining and declaring one
attribute and the related getters, setters and initializing code? I can
think of some macros, but maybe templates would be more elegant
- how can I add some additional callback action for the GUI in an easy to
use way, when a value is changed? I'm using an old 4.1 GCC and I don't
think the nice new C++0x closures are supported
--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
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