Re: Class design issue
"crea" <no@invalid.com> wrote in message
news:zZUbp.34357$2_5.20334@newsfe25.ams2...
Nilone wrote:
On Mar 3, 4:21 pm, "crea" <n...@invalid.com> wrote:
I would make a Weather abstract base class, and derive EarthWeather
(and later MoonWeather, etc) classes from it. I would make a
WeatherChart class that accepts a Weather object in its constructor, a
setter method or its Draw method, depending on its requirements. If
there's a generic Chart class that's suitable, I would have
WeatherChart create an instance of it and delegate to it.
Yes, this is what I wanted, a suggestion. I will think about this... I
have a real application with similar problem right now...
I think your weather class design is good with a base weather and derived
weather classes:
But I think you should keep your chart drawing class seperate and consider
it an extension to the drawing API.
Wthr_chart I presume is full of lots of good GDI code for drawing the chart,
labels , axes, titles, etc. You need a system to transfer the data from a
weather object to the chart. For example your temperature scale maybe min=0,
max=100 for the earth but on venus its different. You can't just plug the
data directly into a chart without some meta data.
You also have timescale, is your weather updated with live transducer data
or is it user data input? Is it reasonable to have one Weather object per
month or per year?
Ok now consider only windspeed data you need something like this:
class windspeed{
int max_windspeed, min_windspeed; /*for min/max scale on graph*/
std::vector<float> windspeed_data;
std::string name;/*"windspeed" */
/*need some kind of date metadata, that is related to your data collection
times.*/
};
Now change this to be a generic weather class:
class WthrData{
int max, int min;
std::vector<float> _data;
std::string name;
/*some time/date structure*/
getDateLimits();
setDateLimits();
appendData();
etc etc;
};
AmazonWthr{
WthrData windspeed;
WthrData humidity;
WthrData humidity;
WthrData humidity;
....
};
VenusWthr{
WthrData windspeed;
WthrData humidity;
WthrData humidity;
WthrData humidity;
....
};
Ok so say you want to graph the weather for July-Oct of a particular year,
how do you select that data? Is the data collected on a daily basis or maybe
4 times a day?
You can't just pass the whole weather object and except the drawing class to
sort it out can you.
So presumably you will have something like:
Wthr_Chart::loadData( int MAX, int MIN, std::vector<float> data ,
std::string name, ??? datelimits );
VenusWthr v1;
Wthr_Chart chart1;
chart1.loadData(v1.windspeed.getMax(), v1.windspeed.getMin(),
v1.windspeed.getData() , v1.windspeed.getName(),
v1.windspeed.getDateLimits() /*pass data for line 1*/)
chart1.loadData(v1.humidity.getMax(), v1.humidity.getMin(),
v1.humidity.getData() , v1.humidity.getName(), v1.humidity.getDateLimits()
/*pass data for line 2*/)
chart1.Draw(HORIZONTAL_LINE_CHART);
The other way is a reversal of this but requires some interfase logic to get
the data, and meta data, into a format acceptable for the graphing
functions. As you were speaking of passing a base pointer to some
intermediate class, I cannot really go into details without know more about
the project, but that type of logic seems like a typical case DLL
..
HTH.