class description - source file - inheritance tree

class TDataMember : public TDictionary

TDataMember TDataMember(G__DataMemberInfo* info = 0, TClass* cl = 0) TDataMember TDataMember(TDataMember&) virtual void ~TDataMember() TClass* Class() virtual Int_t Compare(TObject* obj) Int_t GetArrayDim() const TClass* GetClass() const TDataType* GetDataType() const const char* GetFullTypeName() const Int_t GetMaxIndex(Int_t dim) const virtual const char* GetName() const Int_t GetOffset() const TList* GetOptions() TMethodCall* GetterMethod() virtual const char* GetTitle() const const char* GetTypeName() const virtual ULong_t Hash() virtual TClass* IsA() const Bool_t IsaPointer() const Bool_t IsBasic() const Bool_t IsEnum() const Bool_t IsPersistent() const virtual Long_t Property() const TMethodCall* SetterMethod() virtual void ShowMembers(TMemberInspector& insp, char* parent) virtual void Streamer(TBuffer& b)

Data Members

G__DataMemberInfo* fInfo pointer to CINT data member info TClass* fClass pointer to the class TDataType* fDataType pointer to data basic type descriptor TMethodCall* fValueGetter method that returns a value; TMethodCall* fValueSetter method which sets value; TList* fOptions list of possible values 0=no restrictions

Class Description


 All ROOT classes may have RTTI (run time type identification) support
 added. The data is stored in so called DICTIONARY (look at TDictionary).
 Information about a class is stored in TClass.
 This information may be obtained via the CINT api - see class TCint.
 TClass has a list of TDataMember objects providing information about all
 data members of described class.



 TDataMember provides information about name of data member, its type,
 and comment field string. It also tries to find the TMethodCall objects
 responsible for getting/setting a value of it, and gives you pointers
 to these methods. This gives you a unique possibility to access
 protected and private (!) data members if only methods for doing that
 are defined.
 These methods could either be specified in a comment field, or found
 out automatically by ROOT: here's an example:
 suppose you have a class definition:

        class MyClass{
                Float_t fX1;
                void    SetX1(Float_t x) {fX1 = x;};
                Float_t GetX1()          {return fX1;};

***************************************************************************/ Look at the data member name and method names: a data member name has a prefix letter (f) and has a base name X1 . The methods for getting and setting this value have names which consist of string Get/Set and the same base name. This convention of naming data fields and methods which access them allows TDataMember find this methods by itself completely automatically. To make this description complete, one should know, that names that are automatically recognized may be also: for data fields: either fXXX or fIsXXX; and for getter function GetXXX() or IsXXX() [where XXX is base name]. As an example of using it let's analyse a few lines which get and set a fIsEditable field in TCanvas:

    TCanvas     *c  = new TCanvas("c");   // create a canvas
    TClass      *cl = c->IsA();            // get its class description object.

    TDataMember *dm = cl->GetDataMember("fIsEditable"); //This is our data member

    TMethodCall *getter = dm->GetterMethod(); //find a method that gets value!
    Long_t l;   // declare a storage for this value;

    getter->Execute(c,"",l);  // Get this Value !!!! It will appear in l !!!

    TMethodCall *setter = dm->SetterMethod();
    setter->Execute(c,"0",);   // Set Value 0 !!!

*/ This trick is widely used in ROOT TContextMenu and dialogs for obtaining current values and put them as initial values in dialog fields. If you don't want to follow the convention of naming used by ROOT you still could benefit from Getter/Setter method support: the solution is to instruct ROOT what the names of these routines are. The way to do it is putting this information in a comment string to a data field in your class declaration:

    class MyClass{
        Int_t mydata;  //  *OPTIONS={GetMethod="Get";SetMethod="Set"} 
        Int_t Get(){ return mydata;};
        void  Set(Int_t i){mydata=i;};
*/ However, this getting/setting functions are not the only feature of this class. The next point is providing lists of possible settings for the concerned data member. The idea is to have a list of possible options for this data member, with strings identifying them. This is used in dialogs with parameters to set - for details see TMethodArg, TRootContextMenu, TContextMenu. This list not only specifies the allowed value, but also provides strings naming the options. Options are managed via TList of TOptionListItem objects. This list is also created automatically: if a data type is an enum type, the list will have items describing every enum value, and named according to enum name. If type is Bool_t, two options "On" and "Off" with values 0 and 1 are created. For other types you need to instruct ROOT about possible options. The way to do it is the same as in case of specifying getter/setter method: a comment string to a data field in Your header file with class definition. The most general format of this string is:

*OPTIONS={GetMethod="getter";SetMethod="setter";Items=(it1="title1",it2="title2", ... ) } 

*/ While parsing this string ROOT firstly looks for command-tokens: GetMethod, SetMethod, Items; They must be preceded by string *OPTIONS= , enclosed by {} and separated by semicolons ";". All command token should have a form TOKEN=VALUE. All tokens are optional. The names of getter and setter method must be enclosed by double-quote marks (") . Specifications of Items is slightly more complicated: you need to put token ITEMS= and then enclose all options in curly brackets "()". You separate options by comas ",". Each option item may have one of the following forms: /*
         IntegerValue  = "Text Label"

         EnumValue     = "Text Label"

        "TextValue" = Text Label"

*/ One can sepcify values as Integers or Enums - when data field is an Integer, Float or Enum type; as texts - for Text_t (more precisely: Option_t). As mentioned above - this information are mainly used by contextmenu, but also in Dump() and Inspect() methods and by the THtml class.

TDataMember(G__DataMemberInfo *info, TClass *cl) : TDictionary()
 Default TDataMember ctor. TDataMembers are constructed in TClass
 via a call to TCint::CreateListOfDataMembers(). It parses the comment
 string, initializes optionlist and getter/setter methods.

 TDataMember dtor deletes adopted G__DataMemberInfo object.

Int_t GetArrayDim() const
 Return number of array dimensions.

Int_t GetMaxIndex(Int_t dim) const
 Return maximum index for array dimension "dim".

const char* GetTypeName() const
 Get type of data member, e,g.: "class TDirectory*" -> "TDirectory".
 Result needs to be used or copied immediately.

const char* GetFullTypeName() const
 Get full type description of data member, e,g.: "class TDirectory*".

const char* GetName() const
 Get data member name.

Int_t GetOffset() const
 Get offset from "this". This information is only available for
 public datamembers.

const char* GetTitle() const
 Get data member description string (comment).

Int_t Compare(TObject *obj)
 Compare to other object. Returns 0<, 0 or >0 depending on
 whether "this" is lexicographically less than, equal to, or
 greater than obj.

ULong_t Hash()
 Return hash value for TDataMember based on its name.

Bool_t IsBasic() const
 Return true if data member is a basic type, e.g. char, int, long...

Bool_t IsEnum() const
 Return true if data member is an enum.

Bool_t IsaPointer() const
 Return true if data member is a pointer.

Long_t Property() const
 Get property description word. For meaning of bits see EProperty.

TList* GetOptions()
 Returns list of options - list of TOptionListItems

TMethodCall* GetterMethod()
 Return a TMethodCall method responsible for getting the value of data member

TMethodCall* SetterMethod()
 Return a TMethodCall method responsible for setting the value of data member

Inline Functions

            TClass* GetClass() const
         TDataType* GetDataType() const
             Bool_t IsPersistent() const
            TClass* Class()
            TClass* IsA() const
               void ShowMembers(TMemberInspector& insp, char* parent)
               void Streamer(TBuffer& b)
        TDataMember TDataMember(TDataMember&)

Author: Fons Rademakers 04/02/95
Last update: 2.23/12 26/01/2000 10.02.18 by Rene Brun
Copyright (c) 1995-1999, The ROOT System, All rights reserved. *

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