QOF  0.7.5
Class: Getting and setting entity values.

Modules

 GUID
 
 Entity
 
 Instance
 

Files

file  qofclass.h
 API for registering paramters on objects.
 

Data Structures

struct  _QofParam
 

Macros

#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. More...
 
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. More...
 

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"
 

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.

Macro Definition 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 93 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 169 of file qofclass.h.

typedef void(* QofClassForeachCB)(QofIdTypeConst, gpointer)

Type definition for the class callback function.

Definition at line 275 of file qofclass.h.

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

Type definition for the paramter callback function.

Definition at line 284 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 176 of file qofclass.h.

typedef gint(* QofSortFunc)(gconstpointer, gconstpointer)

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

Definition at line 206 of file qofclass.h.

typedef const gchar* QofType

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

Definition at line 150 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 233 of file qofclass.c.

234 {
235  struct class_iterate qiter;
236 
237  if (!cb)
238  return;
239  if (!classTable)
240  return;
241 
242  qiter.fcn = cb;
243  qiter.data = user_data;
244 
245  g_hash_table_foreach (classTable, class_foreach_cb, &qiter);
246 }
const QofParam* qof_class_get_parameter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the registered Parameter Definition for the requested parameter

Definition at line 146 of file qofclass.c.

147 {
148  GHashTable *ht;
149 
150  g_return_val_if_fail (obj_name, NULL);
151  g_return_val_if_fail (parameter, NULL);
152  if (!check_init ())
153  return NULL;
154 
155  ht = g_hash_table_lookup (classTable, obj_name);
156  if (!ht)
157  {
158  PWARN ("no object of type %s", obj_name);
159  return NULL;
160  }
161 
162  return (g_hash_table_lookup (ht, parameter));
163 }
QofAccessFunc qof_class_get_parameter_getter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the object's parameter getter function

Definition at line 166 of file qofclass.c.

168 {
169  const QofParam *prm;
170 
171  g_return_val_if_fail (obj_name, NULL);
172  g_return_val_if_fail (parameter, NULL);
173 
174  prm = qof_class_get_parameter (obj_name, parameter);
175  if (prm)
176  return prm->param_getfcn;
177 
178  return NULL;
179 }
QofSetterFunc qof_class_get_parameter_setter ( QofIdTypeConst  obj_name,
const gchar *  parameter 
)

Return the object's parameter setter function

Definition at line 182 of file qofclass.c.

184 {
185  const QofParam *prm;
186 
187  g_return_val_if_fail (obj_name, NULL);
188  g_return_val_if_fail (parameter, NULL);
189 
190  prm = qof_class_get_parameter (obj_name, parameter);
191  if (prm)
192  return prm->param_setfcn;
193 
194  return NULL;
195 }
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 198 of file qofclass.c.

200 {
201  const QofParam *prm;
202 
203  if (!obj_name || !param_name)
204  return NULL;
205 
206  prm = qof_class_get_parameter (obj_name, param_name);
207  if (!prm)
208  return NULL;
209 
210  return (prm->param_type);
211 }
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 332 of file qofclass.c.

333 {
334  GList *ref_list;
335  struct param_ref_list b;
336 
337  ref_list = NULL;
338  b.list = NULL;
339  qof_class_param_foreach (type, find_reference_param_cb, &b);
340  ref_list = g_list_copy (b.list);
341  return ref_list;
342 }
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 132 of file qofclass.c.

133 {
134  if (!obj_name)
135  return FALSE;
136  if (!check_init ())
137  return FALSE;
138 
139  if (g_hash_table_lookup (classTable, obj_name))
140  return TRUE;
141 
142  return FALSE;
143 }
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 267 of file qofclass.c.

269 {
270  struct parm_iterate qiter;
271  GHashTable *param_ht;
272 
273  if (!obj_name || !cb)
274  return;
275  if (!classTable)
276  return;
277  param_ht = g_hash_table_lookup (classTable, obj_name);
278  if (!param_ht)
279  return;
280 
281  qiter.fcn = cb;
282  qiter.data = user_data;
283 
284  g_hash_table_foreach (param_ht, param_foreach_cb, &qiter);
285 }
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 93 of file qofclass.c.

95 {
96  GHashTable *ht;
97  int i;
98 
99  if (!obj_name)
100  return;
101  if (!check_init ())
102  return;
103 
104  if (default_sort_function)
105  {
106  g_hash_table_insert (sortTable, (gchar *) obj_name,
107  default_sort_function);
108  }
109 
110  ht = g_hash_table_lookup (classTable, obj_name);
111 
112  /* If it doesn't already exist, create a new table for this object */
113  if (!ht)
114  {
115  ht = g_hash_table_new (g_str_hash, g_str_equal);
116  g_hash_table_insert (classTable, (gchar *) obj_name, ht);
117  }
118 
119  /* At least right now, we allow dummy, parameterless objects,
120  * for testing purposes. Although I suppose that should be
121  * an error.. */
122  /* Now insert all the parameters */
123  if (params)
124  {
125  for (i = 0; params[i].param_name; i++)
126  g_hash_table_insert (ht,
127  (char *) params[i].param_name, (gpointer) & (params[i]));
128  }
129 }