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This file defines a class messaging system reminiscent of traditional OO-style setter and getter interfaces to object properties. More...

Files

file  qofclass.h
 API for registering parameters on objects.
 

Data Structures

struct  QofParam
 This structure is for each queriable parameter in an object. More...
 

Macros

#define QOF_MOD_CLASS   "qof.class"
 

Typedefs

typedef const char * QofType
 Type of Parameters (String, Date, Numeric, GncGUID, etc.)
 
typedef gpointer(* QofAccessFunc) (gpointer object, const QofParam *param)
 The QofAccessFunc defines an arbitrary function pointer for access functions. More...
 
typedef void(* QofSetterFunc) (gpointer, gpointer)
 The QofSetterFunc defines an function pointer for parameter setters. More...
 
typedef gint(* QofCompareFunc) (gpointer a, gpointer b, gint compare_options, QofParam *getter)
 
typedef int(* QofSortFunc) (gconstpointer, gconstpointer)
 This function is the default sort function for a particular object type.
 
typedef void(* QofClassForeachCB) (QofIdTypeConst, gpointer)
 Type definition for the class callback function. More...
 
typedef void(* QofParamForeachCB) (QofParam *, gpointer user_data)
 Type definition for the parameter callback function. More...
 

Functions

void qof_class_register (QofIdTypeConst obj_name, QofSortFunc default_sort_fcn, const QofParam *params)
 This function registers a new object class with the Qof subsystem. More...
 
gboolean qof_class_is_registered (QofIdTypeConst obj_name)
 An example: More...
 
QofType qof_class_get_parameter_type (QofIdTypeConst obj_name, const char *param_name)
 Return the core datatype of the specified object's parameter.
 
const QofParam * qof_class_get_parameter (QofIdTypeConst obj_name, const char *parameter)
 Return the registered Parameter Definition for the requested parameter.
 
QofAccessFunc qof_class_get_parameter_getter (QofIdTypeConst obj_name, const char *parameter)
 Return the object's parameter getter function.
 
QofSetterFunc qof_class_get_parameter_setter (QofIdTypeConst obj_name, const char *parameter)
 Return the object's parameter setter function.
 
void qof_class_foreach (QofClassForeachCB, gpointer user_data)
 Call the callback once for each object class that is registered with the system. More...
 
void qof_class_param_foreach (QofIdTypeConst obj_name, QofParamForeachCB, gpointer user_data)
 Call the callback once for each parameter on the indicated object class. More...
 
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_DATE   "date"
 
#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. More...
 

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

◆ QOF_TYPE_COLLECT

#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 101 of file qofclass.h.

Typedef Documentation

◆ QofAccessFunc

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 177 of file qofclass.h.

◆ QofClassForeachCB

typedef void(* QofClassForeachCB) (QofIdTypeConst, gpointer)

Type definition for the class callback function.

Definition at line 282 of file qofclass.h.

◆ QofParamForeachCB

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

Type definition for the parameter callback function.

Definition at line 290 of file qofclass.h.

◆ QofSetterFunc

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 184 of file qofclass.h.

Function Documentation

◆ qof_class_foreach()

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 222 of file qofclass.cpp.

223 {
224  struct class_iterate iter;
225 
226  if (!cb) return;
227  if (!classTable) return;
228 
229  iter.fcn = cb;
230  iter.data = user_data;
231 
232  g_hash_table_foreach (classTable, class_foreach_cb, &iter);
233 }

◆ qof_class_get_referenceList()

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 ::QofInstanceReference

Definition at line 337 of file qofclass.cpp.

338 {
339  GList *ref_list;
340  struct param_ref_list b;
341 
342  ref_list = NULL;
343  b.list = NULL;
344  qof_class_param_foreach(type, find_reference_param_cb, &b);
345  ref_list = g_list_copy(b.list);
346  return ref_list;
347 }
void qof_class_param_foreach(QofIdTypeConst obj_name, QofParamForeachCB cb, gpointer user_data)
Call the callback once for each parameter on the indicated object class.
Definition: qofclass.cpp:253

◆ qof_class_is_registered()

gboolean qof_class_is_registered ( QofIdTypeConst  obj_name)

An example:

#define MY_OBJ_MEMO "memo" #define MY_OBJ_VALUE "value" #define MY_OBJ_DATE "date" #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_DATE, QOF_TYPE_DATE, myDateGetter, 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 128 of file qofclass.cpp.

129 {
130  if (!obj_name) return FALSE;
131  if (!check_init()) return FALSE;
132 
133  if (g_hash_table_lookup (classTable, obj_name)) return TRUE;
134 
135  return FALSE;
136 }

◆ qof_class_param_foreach()

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 253 of file qofclass.cpp.

255 {
256  struct parm_iterate iter;
257  GHashTable *param_ht;
258 
259  if (!obj_name || !cb) return;
260  if (!classTable) return;
261  param_ht = static_cast<GHashTable*>(g_hash_table_lookup (classTable, obj_name));
262  if (!param_ht) return;
263 
264  iter.fcn = cb;
265  iter.data = user_data;
266 
267  g_hash_table_foreach (param_ht, param_foreach_cb, &iter);
268 }

◆ qof_class_register()

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

This function 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. It may be NULL if there are no parameters to be registered.

Definition at line 89 of file qofclass.cpp.

92 {
93  GHashTable *ht;
94  int i;
95 
96  if (!obj_name) return;
97  if (!check_init()) return;
98 
99  if (default_sort_function)
100  {
101  g_hash_table_insert (sortTable, (char *)obj_name,
102  reinterpret_cast<void*>(default_sort_function));
103  }
104 
105  ht = static_cast<GHashTable*>(g_hash_table_lookup (classTable, obj_name));
106 
107  /* If it doesn't already exist, create a new table for this object */
108  if (!ht)
109  {
110  ht = g_hash_table_new (g_str_hash, g_str_equal);
111  g_hash_table_insert (classTable, (char *)obj_name, ht);
112  }
113 
114  /* At least right now, we allow dummy, parameterless objects,
115  * for testing purposes. Although I suppose that should be
116  * an error.. */
117  /* Now insert all the parameters */
118  if (params)
119  {
120  for (i = 0; params[i].param_name; i++)
121  g_hash_table_insert (ht,
122  (char *)params[i].param_name,
123  (gpointer)&(params[i]));
124  }
125 }