Class: Getting and setting entity values.
[Query Object Framework]


Data Structures

struct  _QofParam

Modules

 GUID
 Entity
 Instance

Files

file  qofclass.h
 API for registering paramters on objects.

Defines

#define QOF_MOD_CLASS   "qof-class"

Typedefs

typedef const gchar * QofType
typedef struct _QofParam QofParam
typedef gpointer(* QofAccessFunc )(gpointer object, const QofParam *param)
typedef void(* QofSetterFunc )(gpointer, gpointer)
typedef gint(* QofSortFunc )(gconstpointer, gconstpointer)
typedef void(* QofClassForeachCB )(QofIdTypeConst, gpointer)
typedef void(* QofParamForeachCB )(QofParam *, gpointer user_data)

Functions

void qof_class_register (QofIdTypeConst obj_name, QofSortFunc default_sort_fcn, const QofParam *params)
 registers a new object class with the Qof subsystem.
gboolean qof_class_is_registered (QofIdTypeConst obj_name)
QofType qof_class_get_parameter_type (QofIdTypeConst obj_name, const gchar *param_name)
const QofParamqof_class_get_parameter (QofIdTypeConst obj_name, const gchar *parameter)
QofAccessFunc qof_class_get_parameter_getter (QofIdTypeConst obj_name, const gchar *parameter)
QofSetterFunc qof_class_get_parameter_setter (QofIdTypeConst obj_name, const gchar *parameter)
void qof_class_foreach (QofClassForeachCB, gpointer user_data)
void qof_class_param_foreach (QofIdTypeConst obj_name, QofParamForeachCB, gpointer user_data)
GList * qof_class_get_referenceList (QofIdTypeConst type)
 List of the parameters that could be references.

Core types

Core data types for objects that can be used in parameters. Note that QofIdTypes may also be used and will create a single reference between two known objects.

#define QOF_TYPE_STRING   "string"
#define QOF_TYPE_TIME   "time"
#define QOF_TYPE_NUMERIC   "numeric"
#define QOF_TYPE_DEBCRED   "debcred"
#define QOF_TYPE_GUID   "guid"
#define QOF_TYPE_INT32   "gint32"
#define QOF_TYPE_INT64   "gint64"
#define QOF_TYPE_DOUBLE   "double"
#define QOF_TYPE_BOOLEAN   "boolean"
#define QOF_TYPE_KVP   "kvp"
#define QOF_TYPE_CHAR   "character"
#define QOF_TYPE_COLLECT   "collection"
 secondary collections are used for one-to-many references between entities and are implemented using QofCollection. These are NOT the same as the main collections in the QofBook.

Detailed Description

This file defines a class messaging system reminiscent of traditional OO-style setter and getter interfaces to object properties. A C-language object can declare a collection of setters and getters on itself that can then be used to perform run-time (as opposed to compile-time) bindings to the object.

To put it differently, a QOF class is a set of parameter getters and setters that are associated with an object type. Given a pointer to some thing, the setters and getters can be used to get and set values out of that thing. Note that the pointer to "some thing" need not be a pointer to a QOF Entity or Instance (although QOF classes are more interesting when used with Entities/Instances). What "some thing" is defined entirely by the programmer declaring a new QOF Class.

Because a QOF Class associates getters and setters with a type, one can then ask, at run time, what parameters are associated with a given type, even if those parameters were not known at compile time. Thus, a QOF Class is sort-of like a DynAny implementation. QOF classes can be used to provide "object introspection", i.e. asking object to describe itself.

The QOF Query subsystem depends on QOF classes having been declared; the Query uses the getters to get values associated with particular instances.

A QofAccessFunc or QofSetterFunc do not need to be public functions, if you need to add functions to an object with an established API, define the additional QOF routines as static. Only the register routine needs to be public.


Define Documentation

#define QOF_TYPE_COLLECT   "collection"

secondary collections are used for one-to-many references between entities and are implemented using QofCollection. These are NOT the same as the main collections in the QofBook.

  1. Each QofCollection contains one or many entities - *all* of a single type.
  2. The entity type within the collection can be determined at run time.
  3. Easy conversions to GList or whatever in the param_setfcn handler.
  4. Each parameter can have its own collection.
  5. Each entity can have a different *type* of collection to its siblings, provided that it is acceptable to the set function.
  6. Each object decides which types are acceptable for which parameter in the set functions. This is then part of the API for that object.

QOF_TYPE_COLLECT has two functions, both related to one-to-many links:

  • Represent a reference between 2 entities with a list of acceptable types. (one object linked to many types of single entities)
  • Represent a reference between one entity and many entities of another type. (one object linked to many entities of a single type.)

If the set function can handle it, it could also be used for true one-to-many links: one object linked to many entities of many types.

n.b. Always subject to each collection holding only one type at runtime. (otherwise use books).

Definition at line 121 of file qofclass.h.


Typedef Documentation

typedef gpointer(* QofAccessFunc)(gpointer object, const QofParam *param)

The QofAccessFunc defines an arbitrary function pointer for access functions. This is needed because C doesn't have templates, so we just cast a lot. Real functions must be of the form:

param_type getter_func (object_type *self); or param_type getter_func (object_type *self, QofParam *param);

The additional argument 'param' allows generic getter functions to be implemented, because this argument provides for a way to identify the expected getter_func return type at runtime. It also provides a place for the user to hang additional user-defined data.

Definition at line 144 of file qofclass.h.

typedef void(* QofClassForeachCB)(QofIdTypeConst, gpointer)

Type definition for the class callback function.

Definition at line 251 of file qofclass.h.

typedef void(* QofParamForeachCB)(QofParam *, gpointer user_data)

Type definition for the paramter callback function.

Definition at line 260 of file qofclass.h.

typedef void(* QofSetterFunc)(gpointer, gpointer)

The QofSetterFunc defines an function pointer for parameter setters. Real functions must be of the form:

void setter_func (object_type *self, param_type *param);

Definition at line 151 of file qofclass.h.

typedef gint(* QofSortFunc)(gconstpointer, gconstpointer)

This function is the default sort function for a particular object type

Definition at line 181 of file qofclass.h.

typedef const gchar* QofType

Type of Paramters (String, Date, Numeric, GUID, etc.)

Definition at line 125 of file qofclass.h.


Function Documentation

void qof_class_foreach ( QofClassForeachCB  ,
gpointer  user_data 
)

Call the callback once for each object class that is registered with the system. The 'user_data' is passed back to the callback.

Definition at line 234 of file qofclass.c.

00235 {
00236     struct class_iterate qiter;
00237 
00238     if (!cb)
00239         return;
00240     if (!classTable)
00241         return;
00242 
00243     qiter.fcn = cb;
00244     qiter.data = user_data;
00245 
00246     g_hash_table_foreach (classTable, class_foreach_cb, &qiter);
00247 }

const QofParam* qof_class_get_parameter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the registered Parameter Definition for the requested parameter

Definition at line 147 of file qofclass.c.

00148 {
00149     GHashTable *ht;
00150 
00151     g_return_val_if_fail (obj_name, NULL);
00152     g_return_val_if_fail (parameter, NULL);
00153     if (!check_init ())
00154         return NULL;
00155 
00156     ht = g_hash_table_lookup (classTable, obj_name);
00157     if (!ht)
00158     {
00159         PWARN ("no object of type %s", obj_name);
00160         return NULL;
00161     }
00162 
00163     return (g_hash_table_lookup (ht, parameter));
00164 }

QofAccessFunc qof_class_get_parameter_getter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the object's parameter getter function

Definition at line 167 of file qofclass.c.

00169 {
00170     const QofParam *prm;
00171 
00172     g_return_val_if_fail (obj_name, NULL);
00173     g_return_val_if_fail (parameter, NULL);
00174 
00175     prm = qof_class_get_parameter (obj_name, parameter);
00176     if (prm)
00177         return prm->param_getfcn;
00178 
00179     return NULL;
00180 }

QofSetterFunc qof_class_get_parameter_setter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the object's parameter setter function

Definition at line 183 of file qofclass.c.

00185 {
00186     const QofParam *prm;
00187 
00188     g_return_val_if_fail (obj_name, NULL);
00189     g_return_val_if_fail (parameter, NULL);
00190 
00191     prm = qof_class_get_parameter (obj_name, parameter);
00192     if (prm)
00193         return prm->param_setfcn;
00194 
00195     return NULL;
00196 }

QofType qof_class_get_parameter_type ( QofIdTypeConst  obj_name,
const gchar *  param_name 
)

Return the core datatype of the specified object's parameter

Definition at line 199 of file qofclass.c.

00201 {
00202     const QofParam *prm;
00203 
00204     if (!obj_name || !param_name)
00205         return NULL;
00206 
00207     prm = qof_class_get_parameter (obj_name, param_name);
00208     if (!prm)
00209         return NULL;
00210 
00211     return (prm->param_type);
00212 }

GList* qof_class_get_referenceList ( QofIdTypeConst  type  ) 

List of the parameters that could be references.

Simple check to return a GList of all parameters of this object type that are not known QOF data types. Used for partial QofBook support, see QofEntityReference

Definition at line 329 of file qofclass.c.

00330 {
00331     GList *ref_list;
00332     struct param_ref_list b;
00333 
00334     ref_list = NULL;
00335     b.list = NULL;
00336     qof_class_param_foreach (type, find_reference_param_cb, &b);
00337     ref_list = g_list_copy (b.list);
00338     return ref_list;
00339 }

gboolean qof_class_is_registered ( QofIdTypeConst  obj_name  ) 

An example:

 #define MY_OBJ_MEMO     "memo"
 #define MY_OBJ_VALUE    "value"
 #define MY_OBJ_TIME     "time"
 #define MY_OBJ_ACCOUNT  "account"
 #define MY_OBJ_TRANS    "trans"

 static QofParam myParams[] = {
 { MY_OBJ_MEMO, QOF_TYPE_STRING, myMemoGetter, NULL },
 { MY_OBJ_VALUE, QOF_TYPE_NUMERIC, myValueGetter, NULL },
 { MY_OBJ_TIME, QOF_TYPE_TIME, myTimeGetter, NULL },
 { MY_OBJ_ACCOUNT, GNC_ID_ACCOUNT, myAccountGetter, NULL },
 { MY_OBJ_TRANS, GNC_ID_TRANS, myTransactionGetter, NULL },
 NULL };

 qof_class_register ("myObjectName", myObjectCompare, &myParams);
 
Return true if the the indicated type is registered, else return FALSE.

Definition at line 133 of file qofclass.c.

00134 {
00135     if (!obj_name)
00136         return FALSE;
00137     if (!check_init ())
00138         return FALSE;
00139 
00140     if (g_hash_table_lookup (classTable, obj_name))
00141         return TRUE;
00142 
00143     return FALSE;
00144 }

void qof_class_param_foreach ( QofIdTypeConst  obj_name,
QofParamForeachCB  ,
gpointer  user_data 
)

Call the callback once for each parameter on the indicated object class. The 'user_data' is passed back to the callback.

Definition at line 268 of file qofclass.c.

00270 {
00271     struct parm_iterate qiter;
00272     GHashTable *param_ht;
00273 
00274     if (!obj_name || !cb)
00275         return;
00276     if (!classTable)
00277         return;
00278     param_ht = g_hash_table_lookup (classTable, obj_name);
00279     if (!param_ht)
00280         return;
00281 
00282     qiter.fcn = cb;
00283     qiter.data = user_data;
00284 
00285     g_hash_table_foreach (param_ht, param_foreach_cb, &qiter);
00286 }

void qof_class_register ( QofIdTypeConst  obj_name,
QofSortFunc  default_sort_fcn,
const QofParam params 
)

registers a new object class with the Qof subsystem.

In particular, it registers the set of setters and getters for controlling the object. The getters are typically used by the query subsystem to query type specific data. Note that there is no particular requirement for there to be a setter for every getter or even vice-versa, nor is there any requirement for these to map 'cleanly' or orthogonally to the underlying object. The parameters are really just a set of value setting and getting routines.

The "params" argument must be a NULL-terminated array of QofParam with a constant storage size. It may be NULL if there are no parameters to be registered. When creating dynamic QofObjects, ensure the array is long enough for all objects. Registration will stop at the first NULL parameter.

Definition at line 94 of file qofclass.c.

00096 {
00097     GHashTable *ht;
00098     int i;
00099 
00100     if (!obj_name)
00101         return;
00102     if (!check_init ())
00103         return;
00104 
00105     if (default_sort_function)
00106     {
00107         g_hash_table_insert (sortTable, (gchar *) obj_name,
00108             default_sort_function);
00109     }
00110 
00111     ht = g_hash_table_lookup (classTable, obj_name);
00112 
00113     /* If it doesn't already exist, create a new table for this object */
00114     if (!ht)
00115     {
00116         ht = g_hash_table_new (g_str_hash, g_str_equal);
00117         g_hash_table_insert (classTable, (gchar *) obj_name, ht);
00118     }
00119 
00120     /* At least right now, we allow dummy, parameterless objects,
00121      * for testing purposes.  Although I suppose that should be
00122      * an error..  */
00123     /* Now insert all the parameters */
00124     if (params)
00125     {
00126         for (i = 0; params[i].param_name; i++)
00127             g_hash_table_insert (ht,
00128                 (char *) params[i].param_name, (gpointer) & (params[i]));
00129     }
00130 }


Generated on Mon Jul 13 05:15:15 2009 for QOF by  doxygen 1.5.9