library: libCore #include "TDataMember.h"

# TDataMember

class description - source file - inheritance tree (.pdf)

## class TDataMember : public TDictionary

| Inheritance Chart:

`TObject`

<-

`TNamed`

<-

`TDictionary`

<-

`TDataMember`

        public:

                          TDataMember(G__DataMemberInfo* info = 0, TClass* cl = 0)
                          TDataMember(const TDataMember&)
                  virtual ~TDataMember()
           static TClass* Class()
                    Int_t GetArrayDim() const
              const char* GetArrayIndex() const
                  TClass* GetClass() const
               TDataType* GetDataType() const
              const char* GetFullTypeName() const
                    Int_t GetMaxIndex(Int_t dim) const
                    Int_t GetOffset() const
                    Int_t GetOffsetCint() const
                   TList* GetOptions() const
             TMethodCall* GetterMethod(TClass* cl = 0)
              const char* GetTrueTypeName() const
              const char* GetTypeName() const
                    Int_t GetUnitSize() const
          virtual TClass* IsA() const
                   Bool_t IsaPointer() const
                   Bool_t IsBasic() const
                   Bool_t IsEnum() const
                   Bool_t IsPersistent() const
                    Int_t IsSTLContainer()
             TDataMember& operator=(const TDataMember&)
           virtual Long_t Property() const
             TMethodCall* SetterMethod(TClass* cl)
             virtual void ShowMembers(TMemberInspector& insp, char* parent)
             virtual void Streamer(TBuffer& b)
                     void StreamerNVirtual(TBuffer& b)

### Data Members

        private:

          G__DataMemberInfo* fInfo          pointer to CINT data member info
                     TClass* fClass         pointer to the class
                  TDataType* fDataType      pointer to data basic type descriptor
                       Int_t fOffset        offset
                       Int_t fSTLCont       STL type
                      Long_t fProperty      Property
                     TString fTypeName      data member type, e,g.: "class TDirectory*" -> "TDirectory".
                     TString fFullTypeName  full type description of data member, e,g.: "class TDirectory*".
                     TString fTrueTypeName  full type description with no typedef
                TMethodCall* fValueGetter   method that returns a value;
                TMethodCall* fValueSetter   method which sets value;
                      TList* fOptions       list of possible values 0=no restrictions

        public:

          static const enum TDataMember:: kObjIsPersistent

## Class Description

      TDataMember.

     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{
                private:
                    Float_t fX1;
                        ...
                public:
                    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 fEditable field in TCanvas:

    /*

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

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

        TMethodCall *getter = dm->GetterMethod(c); //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(c);
        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() const { 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()

     TDataMember dtor deletes adopted G__DataMemberInfo object.

Int_t GetArrayDim() const

     Return number of array dimensions.

const char* GetArrayIndex() const

     If the data member is pointer and has a valid array size in its comments
     GetArrayIndex returns a string pointing to it;
     otherwise it returns an empty string.

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".

const char* GetFullTypeName() const

     Get full type description of data member, e,g.: "class TDirectory*".

const char* GetTrueTypeName() const

     Get full type description of data member, e,g.: "class TDirectory*".

Int_t GetOffset() const

     Get offset from "this".

Int_t GetOffsetCint() const

     Get offset from "this" using the information in CINT only.

Int_t GetUnitSize() const

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.

int IsSTLContainer()

     The return type is defined in TDictionary (kVector, kList, etc.)

Long_t Property() const

     Get property description word. For meaning of bits see EProperty.

TList* GetOptions() const

     Returns list of options - list of TOptionListItems

TMethodCall* GetterMethod(TClass *cl)

     Return a TMethodCall method responsible for getting the value
     of data member. The cl argument specifies the class of the object
     which will be used to call this method (in case of multiple
     inheritance TMethodCall needs to know this to calculate the proper
     offset).

TMethodCall* SetterMethod(TClass *cl)

     Return a TMethodCall method responsible for setting the value
     of data member. The cl argument specifies the class of the object
     which will be used to call this method (in case of multiple
     inheritance TMethodCall needs to know this to calculate the proper
     offset).

### 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)
                    void StreamerNVirtual(TBuffer& b)
             TDataMember TDataMember(const TDataMember&)
            TDataMember& operator=(const TDataMember&)

Author: Fons Rademakers 04/02/95
Last update: root/meta:$Name: $:$Id: TDataMember.cxx,v 1.24 2005/03/03 08:04:16 brun Exp $
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *