Generic QueryValue() Method

[Steve Hyatt]

Hi.

I wrote the following snipped that uses tempalates that can get the value of an attribute with one function:

in TiXmlAttribute:

    #ifdef TIXML_USE_STL
    template <typename DataType>
    int QueryValue(DataType* val) const
    {
        std::stringstream ss(value.c_str());
        if (ss >> *val)
            return TIXML_SUCCESS;
        return TIXML_WRONG_TYPE;
    }
    #endif

Usage:

...
int intVal;
float floatVal;

if (attrib->QueryValue(&intVal) == TIXML_SUCCESS) {
    cout << "int val=" << intVal << endl;
}

if (attrib->QueryValue(&floatVal) == TIXML_SUCCESS) {
    cout << "float val=" << floatVal << endl;
}

...

Would anyone else find this useful?

Steve

[Ellers]

Personally, I'm a fan of templates :)

Two queries come to mind -

- is the #ifdef TIXML_USE_STL the right choice? That is, some people (ok, me) might prefer *not* to have STL, but *do* want to have template methods like this. If so, perhaps use #ifdef TIXML_USE_TEMPLATE_EXTRAS or #ifdef TIXML_USE_ADV?

- is the expression "(ss >> *val)" always going to give a boolean result? Where I say "always" I guess it could mean "for all intents and purposes".

WDYT?

[Steve Hyatt]

Hi.

I use the #ifdef since the function uses the STL stringstream class.

The check for success uses the stream's good() method.  It could be written as:

int QueryValue(DataType* val) const
{
    std::stringstream ss(value.c_str());
    ss >> *val;
    if (ss.good()) 
        return TIXML_SUCCESS;
    return TIXML_WRONG_TYPE;
}

Thoughts?

Steve

[Lee Thomason]

That's clever.

We should put that in after a little testing. (Along with Visit() and the memory leak on error fix...) with the next release.

lee

[Lee Thomason]

Implemented - will be checked in to CVS soon.

Good idea!

lee

[RJP Computing]

Is this close to being checked in. I have a great need for that. Thanks

[Lee Thomason]

I thought it was, but it's not in CVS. That's a little wierd. I'll check it in tonight.

lee

[RJP Computing]

Great! Thanks.

Ryan

[Lee Thomason]

Checked in to CVS, QueryValueAttribute()

lee