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RTTI Part 5. Summary. - Page 2

© Lyapin Ilya

GetPropList(obj.ClassInfo, tkAll, ppList);
GetPropInfos retrieves data for all objects' properties, GetPropList allows to specify a kind (several kinds) of the properties. So if you need only string properties use following code:
GetPropList( Obj.ClassInfo ,[ tkString, tkLString, tkWString], nil);

Declarations of these routines are the same in all Delphi versions.

GetXXX and SetXXX routines.

Through the RTTI you can access property if you know its name. The RTTI provides a series of functions with names like SetOrdProp, GetOrdProp, SetStrProp,GetStrProp and so forth.
function Get<PropType>Prop(Instance: TObject; PropInfo: PPropInfo): <PropType>;
procedure Set<PropType>Prop(Instance: TObject; PropInfo: PPropInfo;
Value: <PropType>);

The first parameter is the object instance, the second is PPropInfo reference to property. The GetXXX functions return value of the property; the SetXXX functions receive a new value as the third parameter.

Each type has its own GetXXX/SetXXX pair. Here is a full listing of these routines:

function GetOrdProp(Instance: TObject; PropInfo: PPropInfo): Longint;
procedure SetOrdProp(Instance: TObject; PropInfo: PPropInfo;
Value: Longint);

function GetStrProp(Instance: TObject; PropInfo: PPropInfo): string;
procedure SetStrProp(Instance: TObject; PropInfo: PPropInfo;
const Value: string);

function GetFloatProp(Instance: TObject; PropInfo: PPropInfo): Extended;
procedure SetFloatProp(Instance: TObject; PropInfo: PPropInfo;
Value: Extended);

function GetVariantProp(Instance: TObject; PropInfo: PPropInfo): Variant;
procedure SetVariantProp(Instance: TObject; PropInfo: PPropInfo;
const Value: Variant);

function GetMethodProp(Instance: TObject; PropInfo: PPropInfo): TMethod;
procedure SetMethodProp(Instance: TObject; PropInfo: PPropInfo;
const Value: TMethod);

The GetInt64Prop and SetInt64Prop routines are added in Delphi 4 in order to access properties of type Int64.

function GetInt64Prop(Instance: TObject; PropInfo: PPropInfo): Int64;
procedure SetInt64Prop(Instance: TObject; PropInfo: PPropInfo;
const Value: Int64);

The following routines are added in Delphi 5
function GetEnumProp(Instance: TObject; PropInfo: PPropInfo): string; procedure SetEnumProp(Instance: TObject; PropInfo: PPropInfo;
const Value: string);

function GetSetProp(Instance: TObject; PropInfo: PPropInfo;
Brackets: Boolean = False): string;
procedure SetSetProp(Instance: TObject; PropInfo: PPropInfo;
const Value: string);

New Delphi 5 features.

There are several so-called 'easy access' routines. They overload standard routines listed above. Each GetXXX/SetXXX routine has an 'easy access' version. The only difference - type of second parameter is string, and the name of property should be specified instead of PPropinfo reference. These routines are implemented like following
function GetEnumProp(Instance: TObject; const PropName: string): string;
begin
Result := GetEnumProp(Instance, GetPropInfo(Instance, PropName));
end;

procedure SetEnumProp(Instance: TObject; const PropName: string;
const Value: string);
begin
SetEnumProp(Instance, GetPropInfo(Instance, PropName), Value);
end;

The call to GetPropInfo is hidden in the 'easy access' routine body.
I prefer to use old style routines in order to make the source code that can be compiled and do the same under all Delphi versions.

Summary.

I hope that this article will simplify usage of undocumented Delphi features. I spent several hours analyzing the typinfo.pas unit sources to retrieve this information, I'm not sure that all is correct so if you find a bug please let me know.

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