Home » Extra libraries, Code snippets, applications etc. » C++ language problems and code snippets » template + convert problem
| template + convert problem [message #23152] |
Sat, 19 September 2009 14:14  |
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I make a table in which multiple fields of reference from other tables. The mapping of the field from another table I made with the converter.
Now it looks as follows:
converts.h
struct ConvCompany : Convert
{
virtual Value Format(const Value& q) const;
};
struct ConvNomencl : Convert
{
virtual Value Format(const Value& q) const;
};
struct ConvManager : Convert
{
virtual Value Format(const Value& q) const;
};
converts.cpp:
Value ConvCompany::Format(const Value &q) const
{
if(q.IsNull()) return Null;
static VectorMap<int, String> comp;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > 600){
comp.Clear();
lastcleartime=GetSysTime();
}
int f = comp.Find(int(q));
if(f >= 0){
return comp[f];
} else {
Sql sql;
sql * Select(COM_NAME).From(COMPANY).Where(COM_ID == q);
String company;
if(sql.Fetch()) {
int sid = int(q);
company = sql[COM_NAME];
comp.Add(sid, company);
} else {
company = "";
}
return company;
}
}
Value ConvNomencl::Format(const Value& q) const
{
if(q.IsNull()) return Null;
static VectorMap<int, String> nom;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > 600){
nom.Clear();
lastcleartime=GetSysTime();
}
int f = nom.Find(int(q));
if(f >= 0){
return nom[f];
} else {
Sql sql;
sql * SqlSelect(NOM_ID,NOM_NAME).From(NOMENCL).Where(NOM_ID == q);
String nomencl;
if(sql.Fetch()) {
int sid = sql[NOM_ID];
nomencl = sql[NOM_NAME];
nom.Add(sid, nomencl);
} else {
nomencl = "";
}
return nomencl;
}
}
Value ConvManager::Format(const Value &q) const
{
if(q.IsNull()) return Null;
static VectorMap<int, String> man;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > 600){
man.Clear();
lastcleartime=GetSysTime();
}
int f = man.Find(int(q));
if(f >= 0){
return man[f];
} else {
Sql sql;
sql * SqlSelect(USR_REALNAME).From(USER).Where(USR_ID == q);
String manager;
if(sql.Fetch()) {
int sid = int(q);
manager = sql[USR_REALNAME];
man.Add(sid, manager);
} else {
manager = "";
}
return manager;
}
}
These converters differ only in the name of the table and field names. I want this to be in the form of a template, something like:
template <SqlId TBL ,SqlId ID, SqlId NAME,int CLEARTIME>
struct ConvDict : Convert
//ConvDict<COMPANY,COM_ID,COM_NAME,600>()
{
virtual Value Format(const Value& q) const {
if(q.IsNull()) return Null;
static VectorMap<int, String> dict;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > CLEARTIME){
dict.Clear();
lastcleartime=GetSysTime();
}
int f = dict.Find(int(q));
if(f >= 0){
return dict[f];
} else {
Sql sql;
sql * Select(NAME).From(TBL).Where(ID == q);
String s;
if(sql.Fetch()) {
int sid = int(q);
s = sql[NAME];
dict.Add(sid, s);
} else {
s = "";
}
return s;
}
}
};
But this code is not compiled, wrote that at this point can not be applied SqlId.
Can someone experienced with this?
How do make a template for the Converter, or Display?
SergeyNikitin<U++>( linux, wine )
{
under( Ubuntu || Debian || Raspbian );
}
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| Re: template + convert problem [message #23160 is a reply to message #23152] |
Sun, 20 September 2009 11:56  |
Didier
Messages: 726
Registered: November 2008
Location: France
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Contributor |
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Hi sergey,
The only words template declaration accepts are: 'class' (or typename) and 'int', all other notations are false and will not compile.
class : means anything, any variable, constant, ... whatever you wan't
int : means only literal integer numbers (1, 2, 1110, 0x10, ...) : no variables !!
But in you're case try this
template <class TBL ,class ID, class NAME,int CLEARTIME>
struct ConvDict : Convert
{
virtual Value Format(const Value& q) const {
if(q.IsNull()) return Null;
static VectorMap<int, String> dict;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > CLEARTIME){
dict.Clear();
lastcleartime=GetSysTime();
}
int f = dict.Find(int(q));
if(f >= 0){
return dict[f];
} else {
Sql sql;
sql * Select(NAME).From(TBL).Where(ID == q);
String s;
if(sql.Fetch()) {
int sid = int(q);
s = sql[NAME];
dict.Add(sid, s);
} else {
s = "";
}
return s;
}
}
};
I haven't tried it, but at least the declaration is correct
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| Re: template + convert problem [message #23161 is a reply to message #23160] |
Sun, 20 September 2009 12:08 |
Didier
Messages: 726
Registered: November 2008
Location: France
|
Contributor |
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After another look, something is missing. You mixed up type passing (template paremeters), and specific value fixing (you're parameters).
You need a constructor, no need for template ! 
The following code compiles:
struct ConvDict : Convert
{
private:
const SqlId TBL;
const SqlId ID;
const SqlId NAME;
const int CLEARTIME;
public:
ConvDict(SqlId tbl ,SqlId id, SqlId name,int clearTime)
: TBL(tbl)
, ID(id)
, NAME(name)
, CLEARTIME(clearTime)
{
}
virtual Value Format(const Value& q) const
{
if(q.IsNull()) return Null;
static VectorMap<int, String> dict;
static Time lastcleartime;
if(GetSysTime()-lastcleartime > CLEARTIME)
{
dict.Clear();
lastcleartime=GetSysTime();
}
int f = dict.Find(int(q));
if(f >= 0)
{
return dict[f];
} else {
Sql sql;
sql * Select(NAME).From(TBL).Where(ID == q);
String s;
if(sql.Fetch()) {
int sid = int(q);
s = sql[NAME];
dict.Add(sid, s);
} else {
s = "";
}
return s;
}
}
};
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