On 28.12.2012 00:58, xrfang wrote:
Hi,
Suppose I have a generic class like this:
type
TSerie = generic class
public
procedure Append(value: T);
end
It should be "generic TSerie<T> = class".
then, in the Append procedure can I do something like:
case *typeof*(T) of
integer: // do something with integer
string: // do someting with string
... ...
end;
Don't use "TypeOf". The function you are looking for is called
"TypeInfo" and works with every type, except Enums with jumps (e.g.
TTestEnum = (teOne := 1, teTwo := 5)).
Here you have an example:
=== source begin ===
program tgentypes;
{$mode objfpc}
uses
typinfo;
type
generic TTest<T> = class
class procedure DoSomething(aArg: T);
end;
{ TTestClass }
class procedure TTest.DoSomething(aArg: T);
var
ti: PTypeInfo;
begin
ti := TypeInfo(aArg);
case ti^.Kind of
tkInteger:
Writeln('Type is an integer');
tkAString:
Writeln('Type is an AnsiString');
tkUString:
Writeln('Type is a UnicodeString');
tkBool:
Writeln('Type is a Boolean');
tkEnumeration:
Writeln('Type is an enumeration');
tkSString:
Writeln('Type is a ShortString');
tkClass:
Writeln('Type is a class');
tkObject:
Writeln('Type is an object');
else
Writeln('Unhandled type: ', ti^.Kind);
end;
end;
type
TTestEnum = (teOne, teTwo, teThree);
TTestObject = object
end;
TTestLongInt = specialize TTest<LongInt>;
TTestAnsiString = specialize TTest<AnsiString>;
TTestUnicodeString = specialize TTest<UnicodeString>;
TTestShortString = specialize TTest<ShortString>;
TTestBoolean = specialize TTest<Boolean>;
TTestTTestEnum = specialize TTest<TTestEnum>;
TTestTObject = specialize TTest<TObject>;
TTestTTestObject = specialize TTest<TTestObject>;
var
obj: TObject;
testobj: TTestObject;
begin
TTestLongInt.DoSomething(42);
TTestAnsiString.DoSomething('Hello World');
TTestUnicodeString.DoSomething('Hello World');
TTestShortString.DoSomething('Hello World');
TTestBoolean.DoSomething(True);
TTestTTestEnum.DoSomething(teOne);
TTestTObject.DoSomething(obj);
TTestTTestObject.DoSomething(testobj);
end.
=== source end ===
For getting the exact value of the argument you need to rely on the
information provided by the RTTI as you can't use e.g. "IntToStr(aArg)"
in case of an integer as you'll get a compiler error when you specialize
the class with something that is not an Integer.
Regards,
Sven
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