delphi的类写在哪里?

delphi的类写在哪里?

tlist=class(tobject) //类tlist的声明
private
datamod:tdatamod; //私有变量
public
//公共方法的定义
function listrec(list_code:string):boolean;
function listsfind(sql:string):boolean;
function lists(findsql:string):olevariant;
procedure listinsert(insertsql:string);
procedure listupdata(updatesql:string);
procedure listdelete(deletesql:string);
//构造方法的声明
constructor create;
destructor destroy;override;
end;
implementation

//构造方法的实现
constructor tlist.create;
begin
datamod:=tdatamod.create(nil);
end;
destructor tlist.destroy;
begin
freeandnil(datamod);
inheritde;
end;

//其他公共方法的实现
function tlist.listrec(list_code:string):boolean;
begin
datamod.adoq2.close;
datamod.adoq2.sql.chear;
datamod.adoq2.sql.add('select * from list_info'+'where list_code='''+list_code'''');
datamod.adoq2.open;
if datamod.adoq2.eof then result:=false
else result:true;
end;
function tlist.listsfind(sql:string):boolean;
begin
datamod.adoq2.close;
datamod.adoq2.sql.clear;
datamod.adoq2.sql.add(sql);
datamod.adoq2.open;
if datamod.adoq2.eof then result:=false
else result:=ture;
end;
procedure tlist.listinsert(insertsql:string);
begin
datamod.adoq2.close;
datamod.adoq2.sql.clear;
datamod.adoq2.sql.add(insertsql);
datamod.adoq2.execsql;
end;
procedure tlist.listupdata(updatasql:string);
begin
datamod.adoq2.close;
datamod.adoq2.sql.clear;
datamod.adoq2.sql.add(updatasql);
datamod.adoq2.execsql;
end;
procedure tlist.listdelete(deletesql:string);
begin
datamod.adoq2.close;
datamod.adoq2.sql.clear;
datamod.adoq2.sql.add(deletesql);
datamod.adoq2.execsql;
end;
function tlist.lists(findsql;string);olevariant;
begin
datamod.sel_adoq1.close;
datamod.sel_adoq1.clear;
datamod.sel_adoq1.add(findsql);
datamod.sel_adoq1.open;
result:datamod.sel_dsp1.data;
end;

tlist=class(tobject)